Polyalkylphenyl and polyalkyloxycarbonylphenyl amino and nitro benzoates and fuel compositions containing the same
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to polyalkylphenyl and polyalkyloxycarbonylphenyl nitrobenzoic acid and amino benzoic acid esters and derivatives thereof. In a further aspect, this invention relates to the use of the aforementioned compounds in fuel compositions to prevent and control engine deposits. 
     2. Description of the Related Art 
     It is well known that automobile engines tend to form deposits on the surface of engine components, such as carburetor ports, throttle bodies, fuel injectors, intake ports and intake valves, due to the oxidation and polymerization of hydrocarbon fuel. These deposits, even when present in relatively minor amounts, often cause noticeable driveability problems, such as stalling and poor acceleration. Moreover, engine deposits can significantly increase an automobile&#39;s fuel consumption and production of exhaust pollutants. Therefore, the development of effective fuel detergents or &#34;deposit control&#34; additives to prevent or control such deposits is of considerable importance and numerous such materials are known in the art. 
     For example, aliphatic hydrocarbon-substituted phenols are known to reduce engine deposits when used in fuel compositions. U.S. Pat. No. 3,849,085, issued Nov. 19, 1974 to Kreuz et al., discloses a motor fuel composition comprising a mixture of hydrocarbons in the gasoline boiling range containing about 0.01 to 0.25 volume percent of a high molecular weight aliphatic hydrocarbon-substituted phenol in which the aliphatic hydrocarbon radical has an average molecular weight in the range of about 500 to 3,500. This patent teaches that gasoline compositions containing minor amounts of an aliphatic hydrocarbon-substituted phenol not only prevent or inhibit the formation of intake valve and port deposits in a gasoline engine, but also enhance the performance of the fuel composition in engines designed to operate at higher operating temperatures with a minimum of decomposition and deposit formation in the manifold of the engine. 
     Similarly, U.S. Pat. No. 4,134,846, issued Jan. 16, 1979 to Machleder et al., discloses a fuel additive composition comprising a mixture of (1) the reaction product of an aliphatic hydrocarbon-substituted phenol, epichlorohydrin and a primary or secondary mono- or polyamine, and (2) a polyalkylene phenol. This patent teaches that such compositions show excellent carburetor, induction system and combustion chamber detergency and, in addition, provide effective rust inhibition when used in hydrocarbon fuels at low concentrations. 
     Amino phenols are also known to function as detergents/dispersants, antioxidants and anti-corrosion agents when used in fuel compositions. U.S. Pat. No. 4,320,021, issued Mar. 16, 1982 to R. M. Lange, for example, discloses amino phenols having at least one substantially saturated hydrocarbon-based substituent of at least 30 carbon atoms. The amino phenols of this patent are taught to impart useful and desirable properties to oil-based lubricants and normally liquid fuels. Similar amino phenols are disclosed in related U.S. Pat. No. 4,320,020, issued Mar. 16, 1982 to R. M. Lange. 
     Similarly, U.S. Pat. No. 3,149,933, issued Sep. 22, 1964 to K. Ley et al., discloses hydrocarbon-substituted amino phenols as stabilizers for liquid fuels. 
     U.S. Pat. No. 4,386,939, issued Jun. 7, 1983 to R. M. Lange, discloses nitrogen-containing compositions prepared by reacting an amino phenol with at least one 3- or 4-membered ring heterocyclic compound in which the hetero atom is a single oxygen, sulfur or nitrogen atom, such as ethylene oxide. The nitrogen-containing compositions of this patent are taught to be useful as additives for lubricants and fuels. 
     Nitro phenols have also been employed as fuel additives. For example, U.S. Pat. No. 4,347,148, issued Aug. 31, 1982 to K. E. Davis, discloses nitro phenols containing at least one aliphatic substituent having at least about 40 carbon atoms. The nitro phenols of this patent are taught to be useful as detergents, dispersants, antioxidants and demulsifiers for lubricating oil and fuel compositions. 
     Similarly, U.S. Pat. No. 3,434,814, issued Mar. 25, 1969 to M. Dubeck et al., discloses a liquid hydrocarbon fuel composition containing a major quantity of a liquid hydrocarbon of the gasoline boiling range and a minor amount sufficient to reduce exhaust emissions and engine deposits of an aromatic nitro compound having an alkyl, aryl, aralkyl, alkanoyloxy, alkoxy, hydroxy or halogen substituent. 
     More recently, certain poly(oxyalkylene) esters have been shown to reduce engine deposits when used in fuel compositions. U.S. Pat. No. 5,211,721, issued May 18, 1993 to R. L. Sung et al., for example, discloses an oil soluble polyether additive comprising the reaction product of a polyether polyol with an acid represented by the formula RCOOH in which R is a hydrocarbyl radical having 6 to 27 carbon atoms. The poly(oxyalkylene) ester compounds of this patent are taught to be useful for inhibiting carbonaceous deposit formation, motor fuel hazing, and as ORI inhibitors when employed as soluble additives in motor fuel compositions. 
     Poly(oxyalkylene) esters of amino- and nitrobenzoic acids are also known in the art. For example, U.S. Pat. No. 2,714,607, issued Aug. 2, 1955 to M. Matter, discloses polyethoxy esters of aminobenzoic acids, nitrobenzoic acids and other isocyclic acids. These polyethoxy esters are taught to have excellent pharmacological properties and to be useful as anesthetics, spasmolytics, analeptics and bacteriostatics. 
     Similarly, U.S. Pat. No. 5,090,914, issued Feb. 25, 1992 to D. T. Reardan et al., discloses poly(oxyalkylene) aromatic compounds having an amino or hydrazinocarbonyl substituent on the aromatic moiety and an ester, amide, carbamate, urea or ether linking group between the aromatic moiety and the poly(oxyalkylene) moiety. These compounds are taught to be useful for modifying macromolecular species such as proteins and enzymes. 
     U.S. Pat. No. 4,328,322, issued Sep. 22, 1980 to R. C. Baron, discloses amino- and nitrobenzoate esters of oligomeric polyols, such as poly(ethylene) glycol. These materials are used in the production of synthetic polymers by reaction with a polyisocyanate. 
     In addition, U.S. Pat. No. 4,231,759, issued Nov. 4, 1980 to Udelhofen et al., discloses a fuel additive composition comprising the Mannich condensation product of (1) a high molecular weight alkyl-substituted hydroxyaromatic compound wherein the alkyl group has a number average molecular weight of about 600 to about 3,000, (2) an amine, and (3) an aldehyde. This patent teaches that such Mannich condensation products provide carburetor cleanliness when employed alone, and intake valve cleanliness when employed in combination with a hydrocarbon carrier fluid. 
     U.S. Pat. No. 4,859,210, issued Aug. 22, 1989 to Franz et al., discloses fuel compositions containing (1) one or more polybutyl or polyisobutyl alcohols wherein the polybutyl or polyisobutyl group has a number average molecular weight of 324 to 3,000, or (2) a poly(alkoxylate) of the polybutyl or polyisobutyl alcohol, or (3) a carboxylate ester of the polybutyl or polyisobutyl alcohol. This patent further teaches that when the fuel composition contains an ester of a polybutyl or polyisobutyl alcohol, the ester-forming acid group may be derived from saturated or unsaturated, aliphatic or aromatic, acyclic or cyclic mono- or polycarboxylic acids. 
     U.S. Pat. Nos. 3,285,855, and 3,330,859 issued Nov. 15, 1966 and Jul. 11, 1967 respectively, to Dexter et al., disclose alkyl esters of dialkyl hydroxybenzoic and hydroxyphenylalkanoic acids wherein the ester moiety contains from 6 to 30 carbon atoms. These patents teach that such esters are useful for stabilizing polypropylene and other organic material normally subject to oxidative deterioration. Similar alkyl esters containing hindered dialkyl hydroxyphenyl groups are disclosed in U.S. Pat. No. 5,196,565, which issued Mar. 23, 1993 to Ross and trialkylhydroxyaromatic carboxylic acids, amides and esters are disclosed in U.S. Pat. No. 4,049,713 which issued Sep. 20, 1977 to Spivack, Also, 4&#39;-hydroxyphenyl propanoate esters are disclosed in U.S. Pat. No. 4,713,475 which issued to Spivack Dec. 15, 1987. 
     U.S. Pat. No. 5,196,142, issued Mar. 23, 1993 to Mollet et al., discloses alkyl esters of hydroxyphenyl carboxylic acids wherein the ester moiety may contain up to 23 carbon atoms. This patent teaches that such compounds are useful as antioxidants for stabilizing emulsion-polymerized polymers. 
     My prior U.S. Pat. No. 5,380,345 discloses certain polyalkyl esters of amino and/or nitro substituted aromatic esters and their use as fuel additives to provide engine deposit control, including intake valve deposit control. 
     SUMMARY OF THE INVENTION 
     I have now discovered certain polyalkylphenyl and polyalkyloxycarbonylphenyl esters of amino and nitro substituted benzoic acid which provide excellent control of engine deposits, especially intake valve deposits, when employed as fuel additives in fuel compositions. 
     The compounds of the present invention include those having the following formula and fuel soluble salts thereof: ##STR2## wherein R is R 3  or --C(O)OR 3  wherein R 3  is a polyalkyl group having an average molecular weight of about from 450 to 5000; R 1  is nitro or --(CH 2 ) x  --NR 4  R 5  wherein R 4  and R 5  are independently hydrogen or lower alkyl having 1 through 6 carbon atoms and x is 0 or 1; and R 2  is hydrogen, hydroxy, nitro or --NR 6  R 7  wherein R 6  and R 7  are independently hydrogen or lower alkyl having 1 through 6 carbon atoms. 
     The present invention further provides a fuel composition comprising a major amount of hydrocarbons boiling in the gasoline or diesel range and a deposit-controlling effective amount of a compound or mixture of compounds, of the present invention. 
     The present invention additionally provides a fuel concentrate comprising an inert stable oleophilic organic solvent boiling in the range of from about 150° F. to 400° F. and from about 10 to 70 weight percent of a compound or mixture of compounds of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Based on performance (e.g. deposit control), handling properties and performance/cost effectiveness, the preferred compounds of the invention are those wherein R 1  is nitro, amino, N-alkylamino, or --CH 2  NH 2  (aminomethyl). More preferably, R 1  is a nitro, amino or --CH 2  NH 2  group. Most preferably, R 1  is an amino or --CH 2  NH 2  group. Preferably, R 2  is hydrogen, hydroxy, nitro or amino. More preferably, R 2  is hydrogen or hydroxy. Most preferably, R 2  is hydrogen. Preferably, R 3  is a polyalkyl group having an average molecular weight in the range of about 700 to 5,000, more preferably about 700 to 3,000, and most preferably about 900 to 2,500. Preferably, the compound has a combination of preferred substituents. 
     When R 1  and/or R 2  is an N-alkylamino group, the alkyl group of the N-alkylamino moiety preferably contains 1 to 4 carbon atoms. More preferably, the N-alkylamino is N-methylamino or N-ethylamino. 
     Similarly, when R 1  and/or R 2  is an N,N-dialkylamino group, each alkyl group of the N,N-dialkylamino moiety preferably contains 1 to 4 carbon atoms. More preferably, each alkyl group is either methyl or ethyl. For example, particularly preferred N,N-dialkylamino groups are N,N-dimethylamino, N-ethyl-N-methylamino and N,N-diethylamino groups. 
     A further preferred group of compounds are those wherein R 1  is amino, nitro, or --CH 2  NH 2  and R 2  is hydrogen or hydroxy. A particularly preferred group of compounds are those wherein R 1  is amino or --CH 2  NH 2  and R 2  is hydrogen. 
     It is preferred that the R 1  substituent is located at the meta or, more preferably, the para position of the benzoic acid moiety, i.e., para or meta relative to the carbonyloxy group linking the two phenyl rings. When R 2  is a substituent other than hydrogen, it is particularly preferred that this R 2  group be in a meta or para position relative to the carbonyloxy linking group and in an ortho position relative to the R 1  substituent. Further, in general, when R 2  is other than hydrogen, it is preferred that one of R 1  or R 2  is located para to the carbonyloxy linking group and the other is located meta to the linking group. Similarly, it is preferred that the R substituent on the other phenyl ring is located para or meta, more preferably para, relative to the carbonyloxy linking group. 
     The compounds of the present invention will generally have a sufficient molecular weight so as to be non-volatile at normal engine intake valve operating temperatures (about 20°-250° C). Typically, the molecular weight of the compounds of this invention will range from about 900 to about 5,500, preferably from 900 to 3,500. 
     Fuel-soluble salts of the compounds of formula I can be readily prepared and such salts are contemplated to be useful for preventing or controlling engine deposits. Suitable salts include, for example, those obtained by protonating the amino moiety with a strong organic acid, such as an alkyl- or arylsulfonic acid. Preferred salts are derived from toluenesulfonic acid and methanesulfonic acid. 
     When the R 2  substituent is a hydroxy group, suitable salts can be obtained by deprotonation of the hydroxy group with a base. Such salts include salts of alkali metals, alkaline earth metals, ammonium and substituted ammonium salts. Preferred salts of hydroxy-substituted compounds include alkali metal, alkaline earth metal and substituted ammonium salts. 
     Definitions 
     As used herein, the following terms have the following meanings unless expressly stated to the contrary. 
     The term &#34;amino&#34; refers to the group: --NH 2 . 
     The term &#34;N-alkylamino&#34; refers to the group: --NHR a  wherein R a  is an alkyl group. The term &#34;N,N-dialkylamino&#34; refers to the group: --NR b  R c , wherein R b  and R c  are alkyl groups. 
     The term &#34;alkyl&#34; refers to both straight- and branched-chain alkyl groups. 
     The term &#34;lower alkyl&#34; refers to alkyl groups having 1 to about 6 carbon atoms and includes primary, secondary and tertiary alkyl groups. Typical lower alkyl groups include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, n-pentyl, n-hexyl and the like. 
     The term &#34;polyalkyl&#34; refers to alkyl groups which are generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have 2 to about 24 carbon atoms, and more preferably, about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene. 
     The term &#34;fuel&#34; or &#34;hydrocarbon fuel&#34; refers to normally liquid hydrocarbons having boiling points in the range of gasoline and diesel fuels. 
     General Synthetic Procedures 
     The polyalkyl nitro, amino and benzyl aromatic esters of this invention may be prepared by the following general methods and procedures. It should be appreciated that where typical or preferred process conditions (e.g., reaction temperatures, times, mole ratios of reactants, solvents, pressures, etc.) are given, other process conditions may also be used unless otherwise stated. Optimum reaction conditions may vary with the particular reactants or solvents used, but such conditions can be determined by one skilled in the art by routine optimization procedures. 
     Those skilled in the art will also recognize that it may be necessary to block or protect certain functional groups while conducting the following synthetic procedures. In such cases, the protecting group will serve to protect the functional group from undesired reactions or to block its undesired reaction with other functional groups or with the reagents used to carry out the desired chemical transformations. The proper choice of a protecting group for a particular functional group will be readily apparent to one skilled in the art. Various protecting groups and their introduction and removal are described, for example, in T. W. Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, Second Edition, Wiley, New York, 1991, and references cited therein. 
     In the present synthetic procedures, a hydroxyl group will preferably be protected, when necessary, as the benzyl or tert-butyldimethylsilyl ether. Introduction and removal of these protecting groups is well described in the art. Amino groups may also require protection and this may be accomplished by employing a standard amino protecting group, such as a benzyloxycarbonyl or a trifluoroacetyl group. Additionally, as will be discussed in further detail hereinbelow, the aromatic esters of this invention having an amino group on the aromatic moiety will generally be prepared from the corresponding nitro derivative. Accordingly, in many of the following procedures, a nitro group will serve as a protecting group for the amino moiety. 
     Moreover, the compounds of this invention having a --CH 2  NH 2  group on the aromatic moiety will generally be prepared from the corresponding cyano derivative, --CN. Thus, in many of the following procedures, a cyano group will serve as a protecting group for the --CH 2  NH 2  moiety. 
     Synthesis 
     Consistent with the use of appropriate protection groups for hydroxy and amino substituents on the benzoic acid, the compounds of formula I can be prepared by the esterification of the correspondingly substituted benzoic acid with the corresponding substituted phenol: ##STR3## wherein R, R 1 , and R2 are as defined herein and wherein hydroxy and free amino substituents on compound A are preferably protected with a suitable protection group, for example, benzyl and nitro, respectively. 
     This reaction is typically conducted by contacting a substituted phenol of formula B with about 0.25 to about 1.5 molar equivalents of the corresponding substituted and protected benzoic acid of formula A in the presence of an acidic catalyst at a temperature in the range of about 70° C. to about 160° C. for about 0.5 to about 48 hours. Suitable acid catalysts for this reaction include p-toluene sulfonic acid, methanesulfonic acid and the like. Optionally, the reaction can be conducted in the presence of an inert solvent, such as benzene, toluene and the like. The water generated by this reaction is preferably removed during the course of the reaction, for example, by azeotropic distillation. 
     The substituted benzoic acids of formula A are generally known compounds and can be prepared from known compounds using procedures or obvious modifications thereof. Representative acids suitable for use as starting materials include, for example, 2-aminobenzoic acid (anthranilic acid), 3-aminobenzoic acid, 4-aminobenzoic acid, 3-amino-4-hydroxybenzoic acid, 4-amino-3-hydroxybenzoic acid, 2-nitrobenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 3-hydroxy-4-nitrobenzoic acid, 4-hydroxy-3-nitrobenzoic acid. When the R 1  substituent is --CH 2  --NR 4  R 5 , suitable starting materials include 4-cyanobenzoic acid and 3-cyanobenzoic acid. 
     Preferred substituted benzoic acids include 3-aminobenzoic acid, 4-aminobenzoic acid, 3-amino-4-hydroxybenzoic acid, 4-amino-3-hydroxybenzoic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, 3-hydroxy-4-nitrobenzoic acid, 4-hydroxy-3-nitrobenzoic acid, 3-cyanobenzoic acid and 4-cyanobenzoic acid. 
     The starting materials of formula B wherein R is polyalkyl are polyalkylphenols and are well known materials and are typically prepared by the alkylation of phenol with the desired polyolefin or chlorinated polyolefin. A further discussion of polyalkylphenols can be found for example in U.S. Pat. No. 4,744,921. The compounds of formula B wherein R is --C(O)O polyalkyl can be prepared by the reaction of hydroxybenzoic acid with a polyalkyl alcohol. 
     The polyalkyl alcohols may also be prepared by conventional procedures known in the art. For example, polyalkyl alcohols can be prepared from the corresponding olefins by conventional procedures. Such procedures include hydration of the double bond to give an alcohol. Suitable procedures for preparing such long-chain alcohols are described in I. T. Harrison and S. Harrison, Compendium of Organic Synthetic Methods, Wiley-Interscience, New York (1971), pp. 119-122, as well as in U.S. Pat. Nos. 5,055,607 to Buckley and 4,859,210 to Franz et al., the disclosures of which are incorporated herein by reference. 
     Likewise, the polyalkylphenols of formula B wherein Y is polyalkyl may be prepared from the corresponding olefins by conventional procedures. For example, the polyalkylphenols of formula B above may be prepared by reacting the appropriate olefin or olefin mixture with phenol in the presence of an alkylating catalyst at a temperature of from about 60° C. to 200° C., and preferably 125° C. to 180° C. either neat or in an essentially inert solvent at atmospheric pressure. A preferred alkylating catalyst is a sulfonic acid catalyst such as Amberlyst 15® available from Rohnm and Haas, Philadelphia, Pa. Molar ratio of reactants may be used. Alternatively, molar excess of phenol can be employed, i.e., 2-2.5 equivalents of phenol for each equivalent of olefin with unreacted phenol recycled. The latter process maximizes monoalkylphenol. Examples of inert solvents include benzene, toluene, chlorobenzene and 250 thinner which is a mixture of aromatics, paraffins and naphthenes. 
     The polyalkyl substituent on the polyalkyl alcohols and polyalkylphenols employed in the invention are generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have 2 to about 24 carbon atoms, and more preferably, about 3 to 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene. 
     The preferred polyisobutenes used to prepare the presently employed polyalkyl alcohols and polyalkylphenols are polyisobutenes which comprise at least about 20% of the more reactive methylvinylidene isomer, preferably at least 50% and more preferably at least 70%. Suitable polyisobutenes include those prepared using BF 3  catalysts. The preparation of such polyisobutenes in which the methylvinylidene isomer comprises a high percentage of the total composition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808. Such polyisobutenes, known as &#34;reactive&#34; polyisobutenes, yield high molecular weight alcohols in which the hydroxyl group is at or near the end of the hydrocarbon chain. Examples of suitable polyisobutenes having a high alkylvinylidene content include Ultravis 30, a polyisobutene having a number average molecular weight of about 1300 and a methylvinylidene content of about 74%, and Ultravis 10, a polyisobutene having a number average molecular weight of about 950 and a methylvinylidene content of about 76%, both available from British Petroleum. 
     The esterification of the hydroxybenzoic acid with the polyalkyl ol may be conducted under similar conditions to that desired above with respect to the esterification of compound A with compound B including the use of appropriate protection groups. Further, details regarding the preparation of the polyalkyloxycarbonylphenyl compounds can be had by reference to U.S. Pat. No. 5,399,178. 
     The compounds formula I or their suitably protected analogs also can be prepared by reacting the starting material of formula B with an acid halide of the substituted benzoic acid of formula A such as an acid chloride or acid bromide. This can be represented by the following reaction equation: ##STR4## wherein X is halide, typically chloride or bromide, and R, R 1 , and R 2  are as defined herein above, and wherein any hydroxy or free amino substituents on compound A&#39; are preferably protected with a suitable protection group, for example, benzyl or nitro, respectively. Also, when R 1  is --CH 2  NR 4  R 5 , a suitable starting material is a cyanobenzoyl halide. 
     Typically, this reaction is conducted by contacting the phenol compound B with about 0.9 to about 1.5 molar equivalents of the acid halide compound A&#39; in an inert solvent, such as, for example, toluene, dichloromethane, diethyl ether, and the like, at a temperature in the range of about 25° C. to about 150° C. The reaction is generally complete in about 0.5 to about 48 hours. Preferably, the reaction is conducted in the presence of a sufficient amount of an amine capable of neutralizing the acid generated during the reaction, such as, for example, triethylamine, di(isopropyl)ethylamine, pyridine or 4-dimethylaminopyridine. 
     When the acids of formula A or acid halides of formula A&#39; contain a hydroxyl group, protection of the aromatic hydroxyl groups may be accomplished using well-known procedures. The choice of a suitable protecting group for a particular hydroxybenzoic carboxylic acid will be apparent to those skilled in the art. Various protecting groups, and their introduction and removal, are described, for example, in T. W. Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, Second Edition, Wiley, New York, 1991, and references cited therein. 
     After completion of the esterification, deprotection of the aromatic hydroxyl group can also be accomplished using conventional procedures. Appropriate conditions for this deprotection step will depend upon the protecting group(s) utilized in the synthesis and will be readily apparent to those skilled in the art. For example, benzyl protecting groups may be removed by hydrogenolysis under 1 to about 4 atmospheres of hydrogen in the presence of a catalyst, such as palladium on carbon. Typically, this deprotection reaction is conducted in an inert solvent, preferably a mixture of ethyl acetate and acetic acid, at a temperature of from about 0° C. to about 40° C. for about 1 to about 24 hours. 
     When the acids of formula A or acyl halides of formula A&#39; have a free amino group (--NH 2 ) on the phenyl moiety, it is generally desirable to first prepare the corresponding nitro compound (i.e., where R 1  and/or R 2  is a nitro group) using the above-described synthetic procedures, including preparation of the acyl halides, and then reduce the nitro group to an amino group using conventional procedures. Aromatic nitro groups may be reduced to amino groups using a number of procedures that are well known in the art. For example, aromatic nitro groups may be reduced under catalytic hydrogenation conditions; or by using a reducing metal, such as zinc, tin, iron and the like, in the presence of an acid, such as dilute hydrochloric acid. Generally, reduction of the nitro group by catalytic hydrogenation is preferred. Typically, this reaction is conducted using about 1 to 4 atmospheres of hydrogen and a platinum or palladium catalyst, such as palladium on carbon. The reaction is typically carried out at a temperature of about 0° C. to about 100° C. for about 1 to 24 hours in an inert solvent, such as ethanol, ethyl acetate and the like. Hydrogenation of aromatic nitro groups is discussed in further detail in, for example, P. N. Rylander, Catalytic Hydrogenation in Organic Synthesis, pp. 113-137, Academic Press (1979); and Organic Synthesis, Collective Vol. I, Second Edition, pp. 240-241, John Wiley &amp; Sons, Inc. (1941); and references cited therein. 
     Likewise, when the acids of formula A or acyl halides of formula A&#39; contain a --CH 2  NH 2  group on the phenyl moiety, it is generally desirable to first prepare the corresponding cyano compounds (i.e., where R 1  and/or R 2  is a --CN group), and then reduce the cyano group to a --CH 2  NH 2  group using conventional procedures. Aromatic cyano groups may be reduced to --CH 2  NH 2  groups using procedures well known in the art. For example, aromatic cyano groups may be reduced under catalytic hydrogenation conditions similar to those described above for reduction of aromatic nitro groups to amino groups. Thus, this reaction is typically conducted using about 1 to 4 atmospheres of hydrogen and a platinum or palladium catalyst, such as palladium on carbon. Another suitable catalyst is a Lindlar catalyst, which is palladium on calcium carbonate. The hydrogenation may be carried out at temperatures of about 0° C. for about 1 to 24 hours in an inert solvent such as ethanol, ethyl acetate, and the like. Hydrogenation of aromatic cyano groups is further discussed in the references cited above for reduction of aromatic nitro groups. 
     The acyl halides of formula A&#39; can be prepared by contacting the corresponding acid compound of formula A with an inorganic acid halide, such as thionyl chloride, phosphorous trichloride, phosphorous tribromide, or phosphorous pentachloride; or with oxalyl chloride. Typically, this reaction will be conducted using about 1 to 5 molar equivalents of the inorganic acid halide or oxalyl chloride, either neat or in an inert solvent, such as diethyl ether, at a temperature in the range of about 20° C. to about 80° C. for about 1 to about 48 hours. A catalyst, such as N,N-dimethylformamide, may also be used in this reaction. Again it is preferred to first protect any hydroxy or amino substituents before converting the benzoic acid to the acyl halide. 
     Fuel Compositions 
     The compounds of the present invention are useful as additives in hydrocarbon fuels to prevent and control engine deposits, particularly intake valve deposits. The proper concentration of additive necessary to achieve the desired deposit control varies depending upon the type of fuel employed, the type of engine, and the presence of other fuel additives. 
     In general, the concentration of the compounds of this invention in hydrocarbon fuel will range from about 50 to about 2500 parts per million (ppm) by weight, preferably from 75 to 1,000 ppm. When other deposit control additives are present, a lesser amount of the present additive may be used. 
     The compounds of the present invention may be formulated as a concentrate using an inert stable oleophilic (i.e., dissolves in gasoline) organic solvent boiling in the range of about 150° F. to 400° F. (about 65° C. to 205° C.). Preferably, an aliphatic or an aromatic hydrocarbon solvent is used, such as benzene, toluene, xylene or higher-boiling aromatics or aromatic thinners. Aliphatic alcohols containing about 3 to 8 carbon atoms, such as isopropanol, isobutylcarbinol, n-butanol and the like, in combination with hydrocarbon solvents are also suitable for use with the present additives. In the concentrate, the amount of the additive will generally range from about 10 to about 70 weight percent, preferably 10 to 50 weight percent, more preferably from 20 to 40 weight percent. 
     In gasoline fuels, other fuel additives may be employed with the additives of the present invention, including, for example, oxygenates, such as t-butyl methyl ether, antiknock agents, such as methylcyclopentadienyl manganese tricarbonyl, and other dispersants/detergents, such as hydrocarbyl amines, hydrocarbyl poly(oxyalkylene) amines, or succinimides. Additionally, antioxidants, metal deactivators and demulsifiers may be present. 
     In diesel fuels, other well-known additives can be employed, such as pour point depressants, flow improvers, cetane improvers, and the like. 
     A fuel-soluble, nonvolatile carrier fluid or oil may also be used with the polyalkyl aromatic esters of this invention. The carrier fluid is a chemically inert hydrocarbon-soluble liquid vehicle which substantially increases the nonvolatile residue (NVR), or solvent-free liquid fraction of the fuel additive composition while not overwhelmingly contributing to octane requirement increase. The carrier fluid may be a natural or synthetic oil, such as mineral oil, refined petroleum oils, synthetic polyalkanes and alkenes, including hydrogenated and unhydrogenated polyalphaolefins, and synthetic polyoxyalkylene-derived oils, such as those described, for example, in U.S. Pat. No. 4,191,537 to Lewis, and polyesters, such as those described, for example, in U.S. Pat. Nos. 3,756,793 and 5,004,478 to Robinson and Vogel et al., respectively, and in European Patent Application Nos. 356,726 and 382,159, published Mar. 7, 1990 and Aug. 16, 1990, respectively. 
     These carrier fluids are believed to act as a carrier for the fuel additives of the present invention and to assist in removing and retarding deposits. The carrier fluid may also exhibit synergistic deposit control properties when used in combination with a polyalkyl aromatic ester of this invention. 
     The carrier fluids are typically employed in amounts ranging from about 100 to about 5000 ppm by weight of the hydrocarbon fuel, preferably from 400 to 3000 ppm of the fuel. Preferably, the ratio of carrier fluid to deposit control additive will range from about 0.5:1 to about 10:1, more preferably from 1:1 to 4:1, most preferably about 2:1. 
     When employed in a fuel concentrate, carrier fluids will generally be present in amounts ranging from about 20 to about 60 weight percent, preferably from 30 to 50 weight percent. 
     PREPARATIONS AND EXAMPLES 
     A further understanding of the invention can be had in the following nonlimiting Examples. Wherein unless expressly stated to the contrary, all temperatures and temperature ranges refer to the Centigrade system and the term &#34;ambient&#34; or &#34;room temperature&#34; refers to about 20° C.-25° C. The term &#34;percent&#34; or &#34;%&#34; refers to weight percent and the term &#34;mole&#34; or &#34;moles&#34; refers to gram moles. The term &#34;equivalent&#34; refers to a quantity of reagent equal in moles, to the moles of the preceding or succeeding reactant recited in that example in terms of finite moles or finite weight or volume. Where given, proton-magnetic resonance spectrum (p.m.r. or n.m.r.) were determined at 300 mHz, signals are assigned as singlets (s), broad singlets (bs), doublets (d), double doublets (dd), triplets (t), double triplets (dt), quartets (q), and multiplets (m), and cps refers to cycles per second. 
     EXAMPLE 1 
     Preparation of Polyisobutyl Phenol 
     To a flask equipped with a magnetic stirrer, reflux condenser, thermometer, addition funnel and nitrogen inlet was added 203.2 grams of phenol. The phenol was warmed to 40° C. and the heat source was removed. Then, 73.5 milliliters of boron trifluoride etherate was added dropwise. 1040 grams of Ultravis 10 Polyisobutene (moledular weight 950, 76% methylvinylidene, available from British Petroleum) was dissolved in 1,863 milliliters of hexane. The polyisobutene was added to the reaction at a rate to maintain the temperature between 22° C.-27° C. The reaction mixture was stirred for 16 hours at room temperature. Then, 400 milliliters of concentrated ammonium hydroxide was added followed by 2,000 milliliters of hexane. The reaction mixture was washed with water (3×2,000 milliliters), dried over magnesium sulfate, filtered and the solvents removed under vacuum to yield 1,056.5 grams of a crude reaction product. The crude reaction product was determined to contain 80% of the desired product by proton NMR and chromatography on silica gel eluting with hexane, followed by hexane: ethylacetate: ethanol (93:5:2). 
     EXAMPLE 2 
     Preparation of ##STR5## 
     4-Nitrobenzoyl chloride (3.3 grams), 4- polyisobutyl phenol (17.6 grams, prepared as in Example 1), 4-dimethylaminopyridine (2.3 grams) and anhydrous toluene (200 mL) were combined. The resulting mixture was refluxed under nitrogen for 16 hours. The reaction was diluted with 400 mL of hexane and was washed twice with 1% aqueous hydrochloric acid, twice with saturated aqueous sodium bicarbonate solution and once with brine. The organic layer was dried over anhydrous magnesium sulfate, filtered and the solvents removed in vacuo to yield 21.1 grams of the desired product as a yellow oil. 
     EXAMPLE 3 
     Preparation of ##STR6## 
     A solution of 12.3 grams of the product from Example 2 in 200 mL of ethyl acetate containing 1.0 grams of 10% palladium on charcoal was hydrogenolyzed at 35-40 psi for 16 hours on a Parr low-pressure hydrogenator. Catalyst filtration and removal of the solvent in vacuo yield 11.6 grams as a creamy white wax. The wax was chromatographed on silica gel, eluting with hexane/diethyl ether (70:30), and then hexane/diethyl ether (30:70) to yield 8.1 grams of the desired product. 1H NMR (CDCl3) d 8.0 (d, 2H), 7.4 (d, 2H), 7.1 (d, 2H), 6.7 (d, 2H), 4.1(bs, 2H), 0.7-1.8 (m, 137H). 
     EXAMPLE 4 
     Preparation of ##STR7## 
     4-Cyanobenzoyl chloride (2.5 grams), 4-polyisobutyl phenol (15.0 grams, prepared as in Example 1), 4-dimethylaminopyridine (1.9 grams) and anhydrous toluene (300 mL) were combined. The resulting mixture was refluxed under nitrogen for 16 hours. The reaction was diluted with 600 mL of hexane and was washed twice with 1% aqueous hydrochloric acid, twice with saturated aqueous sodium bicarbonate solution and once with brine. The organic layer was dried over anhydrous magnesium sulfate, filtered and the solvents removed in vacuo to yield 16.4 grams as a yellow oil. 
     EXAMPLE 5 
     Preparation of ##STR8## 
     A solution of 16.4 grams of the product from Example 4 in 100 mL of ethyl acetate and 100 mL of acetic acid containing 1.0 gram of 10% palladium on charcoal was hydrogenolyzed at 35-40 psi for 16 hours on a Parr low-pressure hydrogenator. The catalyst was filtered, the residual acetic acid was removed with toluene in vacuo, and the residue was diluted with diethyl ether (300 mL). The diethyl ether was washed twice with saturated aqueous sodium bicarbonate solution and once with brine. The organic layer was dried over anhydrous sodium sulfate, filtered and the solvents removed in vacuo to yield 11.3 grams as a black oil. The oil was chromatographed on silica gel, eluting with hexane/ethyl acetate (90:10), then hexane/diethyl ether/methanol/isopropylamine (40:40:15:5) to yield 3.8 grams of the desired product as a black oil. IR (neat) 1746 cm-1; 1H NMR (CDCl3) d 8.2-7.05(m, 8H), 3.9(s, 2H), 0.7-1.5(m, 137H). 
     EXAMPLE 6 
     Preparation of Polyisobutyl 4-Hydroxybenzoate 
     To a flask equipped with a mechanical stirrer, thermometer, Dean Stark trap, reflux condensor and nitrogen inlet was added 525 grams of polyisobutanol (average molecular weight 984, prepared via hydroformylation of polyisobutene sold under the trademark Amoco H-100), 124.7 grams of 4-hydroxybenzoic acid, and 13.0 grams of p-toluenesulfonic acid. The mixture was stirred at 130° C. for 16 hours, cooled to room temperature and diluted with 2 liters of diethyl ether. The organic phase was washed two times with saturated aqueous sodium bicarbonate, once with brine, dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo to yield 514.3 grams of the desired product as a yellow oil. IR (neat) 1715, 1685 cm -1  ;  1  H NMR (CDCl 3 ) δ7.95 (d,2H), 6.9 (d, 2H), 5.8 (bs, 1H), 4.3 (t, 2H), 0.6-1.8 (m, 139H). 
     EXAMPLE 7 
     Preparation of ##STR9## 
     4-Nitrobenzoyl chloride (11.0 grams), polyisobutyl 4-hydroxybenzoate (63.0 grams, prepared as in Example 6), 4-dimethylaminopyridine (7.6 grams) and anhydrous toluene (500 mL) were combined. The resulting mixture was refluxed under nitrogen for 16 hours. The reaction was diluted with 1.2 L of hexane and was washed twice with 1% aqueous hydrochloric acid, twice with saturated aqueous sodium bicarbonate solution and once with brine. The organic layer was dried over anhydrous magnesium sulfate, filtered and the solvents removed in vacuo to yield 68.1 grams of the desired product as a brown oil.  1  H NMR (CDCL 3 ) d 8.4 (AB quartet, 4H), 8.15 (d, 2H), 7.3 (d, 2H), 4.3 (t, 2H), 0.7-1.8 (m, 139H). 
     EXAMPLE 8 
     Preparation of ##STR10## 
     A solution of 65.0 grams of the product from Example 7 in 500 mL of ethyl acetate containing 3.0 grams of 10% palladium on charcoal was hydrogenolyzed at 35-40 psi for 16 hours on a Parr low-pressure hydrogenator. Catalyst filtration and removal of the solvent in vacuo yielded 56.4 grams of the desired product as a brown oil.  1  H NMR (CDCl 3 ) d 8.1 (d, 2H), 7.95 (d, 2H), 7.3 (d, 2H), 6.7 (d, 2H), 4.3(t, 2H), 4.2(bs, 2H), 0.7-1.8 (m, 139H). 
     EXAMPLE 9 
     Preparation of ##STR11## 
     4-Cyanobenzoyl chloride (2.2 grams ), polyisobutyl 4-hydroxybenzoate (14.0 grams, prepared as in Example 6), 4-dimethylaminopyridine (1.7 grams) and anhydrous toluene (200 mL) were combined. The resulting mixture was refluxed under nitrogen for 16 hours. The reaction was diluted with 600 mL of hexane and was washed twice with 1% aqueous hydrochloric acid, twice with saturated aqueous sodium bicarbonate solution and once with brine. The organic layer was dried over anhydrous magnesium sulfate, filtered and the solvents removed in vacuo to yield 15.1 grams as a yellow oil. 
     EXAMPLE 10 
     Preparation of ##STR12## 
     A solution of 15.1 grams of the product from Example 9 in 100 mL of ethyl acetate and 100 mL of acetic acid containing 1.0 gram of 10% palladium on charcoal was hydrogenolyzed at 35-40 psi for 16 hours on a Parr low-pressure hydrogenator. The catalyst was filtered, the residual acetic acid was removed with toluene in vacuo. The residue was diluted with diethyl ether (300 mL), washed twice with saturated aqueous sodium bicarbonate solution and once with brine. The organic layer was dried over anhydrous sodium sulfate, filtered and the solvents removed in vacuo to yield 13.8 grams as a black oil. The oil was chromatographed on silica gel, eluting with hexane/ethyl acetate (90:10) then hexane/diethyl ether/methanol/isopropylamine (40:40:15:5) to yield 5.2 grams of the desired product as a black oil.  1  H NMR (CDCl 3 ) d 8.2-6.8(m, 8H), 4.3(t, 2H), 3.9(s, 2H), 0.7-1.8(m, 139H). 
     EXAMPLE 11 
     Single-Cylinder Engine Test 
     The test compounds were blended in gasoline and their deposit reducing capacity determined in an ASTM/CFR single-cylinder engine test. 
     A Waukesha CFR single-cylinder engine was used. Each run was carried out for 15 hours, at the end of which time the intake valve was removed, washed with hexane and weighed. The previously determined weight of the clean valve was subtracted from the weight of the value at the end of the run. The differences between the two weights is the weight of the deposit. A lesser amount of deposit indicates a superior additive. The operating conditions of the test were as follows: water jacket temperature 200° F.; vacuum of 12 in Hg, air-fuel ratio of 12, ignition spark timing of 400 BTC; engine speed is 1800 rpm; the crankcase oil is a commercial 30W oil. 
     The amount of carbonaceous deposit in milligrams on the intake valves is reported for each of the test compounds in Table I and Table II. 
     
                       TABLE I                                                     
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         Intake Valve Deposit Weight                                      
         (in milligrams)                                                  
Sample.sup.1                                                              
           Run 1       Run 2   Average                                    
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Base Fuel  288.1       306.2   297.2                                      
Example 3   0.6         2.8     1.7                                       
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 .sup.1 At 150 parts per million actives (ppma).                          
 
    
     
                       TABLE II                                                    
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         Intake Valve Deposit Weight                                      
         (in milligrams)                                                  
Sample.sup.1                                                              
           Run 1       Run 2   Average                                    
______________________________________                                    
Base Fuel  323.8       312.1   318.0                                      
Example 5   25.4        28.0   26.7                                       
Example 7  210.3       212.4   211.4                                      
Example 8   11.8        8.1    10.0                                       
Example 10 118.3        65.0   91.7                                       
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 .sup.1 At 125 parts per million actives (ppma).                          
 
    
     The base fuel employed in the above single-cylinder engine tests was a regular octane unleaded gasoline containing no fuel detergent. The test compounds were admixed with the base fuel to give the concentrations indicated in the tables. 
     The data in Table I and Table II illustrates the significant reduction in intake valve deposits provided by the polyalkylphenyl and polyalkyloxycarbonylphenyl nitro and amino benzoates of the present invention (Examples 3, 5, 7, 8 and 10) compared to the base fuel.