2-Substituted -1,2,4-thiadiazolo-(2,3-a)benzimidazoles and process for their preparation
Uiiited States Patent 1 Beard [451 Apr. 29, 1975 Z-SUBSTITUTED -1,2,4-THlADlAZOL0-(2,3- A)BENZIMIDAZOLES AND PROCESS FOR THEIR PREPARATION [75] Inventor: Colin C. Beard, Palo Alto, Calif.  
 [73] Assignee: Syntex (U.S.A.) Inc., Palo Alto,  
 Calif.  
 [22] Filed: Oct. 4, 1973 [21] Appl. No.: 403,474  
 [52] US. Cl. ..260/306.8 F; 260/250 BN; 260/256.5 R;  
  424/263; 424/270 [51] Int. Cl C07d 99/10 OTHER PUBLICATIONS Chekril et al., Chem. Abstracts, 7818431 ly (1973).  
 Primary Examiner-Richard J. Gallagher Attorney, Agent, or FirmGerard A. Blaufarb; Leon Simon; William B. Walker [57] ABSTRACT Novel I 2-substituted-1,2,4-thiadiazol0-[2,3-a]- benzimidazoles of the formula and the pharmaceutically acceptable salts thereof; and process for their preparation. These 2-substitutedl,2,4-thiadiazolo-[2,3-al-benzimidazoles are useful as fungistatic and fungicidal agents.  
 15 Claims, N0 Drawings Z-SUBSTITUTED -1,2,4-THIADIAZOLQ-(2,3-A)BENZIMIDAZOI:,ES AND PROCESS FOR THEIR PREPARATION This invention relates to novel 2-substituted-l,2.4- thiadiazolo-[2,3-a]-benzimidazole compounds of the formula:  
 wherein R is 1R3 I N r F ii- N I I R is hydrogen or lower alkyl; and the pharmaceutically acceptable salts thereof, and processes for the preparation thereof.  
  The terms lower alkoxy, lower alkyl, lower alkylthio, and lower alkylsulfinyl as used above and in the claims are inclusive of moieties containing from 1 to 4 carbon atoms, for example, methyl, ethyl, propyl, isopropyl, butyl and tert.-butyl.  
  The term -halo&#34; as used above and in the claims is inclusive of chloro, bromo, fluoro and iodo.  
  The compounds of Formula I are chemotherapeutic agents which possess fungistatic and fungicidal properties and thus are useful in combatting fungus infections.  
  Amonst the Amongst against which the compounds of Formula I exhibit fungistatic and fungicidal activity are:  
 M. amlounini H. gramineum E. floccuxmn M. gypsum T. mmlagrophymv Mr (unis C. alhicans T. ruhrum Cr. &#34;(&#39;OfiIIIlMIIS T. wnsuram&#34; R. .rulani T. .l&#39;(&#39;hllt&#39;llf(&#39;illii A. .voluni Particularly preferred are those compounds of Formula I wherein R is phenyl, 4-chlorophenyl, 4- methoxyphenyl, 4-methylphenyl, 4-methylthiophenyl, 4-methylsulfinylphenyl, 4-tert.-butylphenyl, 4-trifluoromethylphenyl, 2-furyl, 3-furyl, Z-naphthyl, 2- thienyl, 3-thienyl, Z-thiazolyl, 4-thiazolyl, S-thiazolyl, 2-methyl-4-thiazolyl, Z-pyridyl, 3-pyridyl, 4-pyridyl. 2- pyrazinyl, 3-isothiazolyl, 4-isothiazolyl. S-isothiazolyl. l,2,3-thiadiazolyl, and 1,2.5-thiadiazolyl.  
  The compounds of Formula I are prepared according to the following generalized reaction scheme:  
  The Z-substituted l,2,4-thiadiazolo-[ 2,3-a benzimidazole compounds of Formula I are obtained by treating the compounds of Formula IV with an oxidizing agent, e.g., m-chloroperbenzoic acid, bromine, chlorine, sulfuryl chloride, peracetic acid, hydrogen peroxide, and the like, at a temperature of from about 40 to 40C., for from about one-fourth to 6 hours, in an inert organic solvent, e.g., chloroform, and the like. When the reaction is carried out using bromine or chlorine it is preferred that the temperature be between about and 30C. In addition, when the oxidation rewherein R is defined as above.  
  The carbonylamino compounds of Formula III are obtained by treating the 2-aminobenzimidazole of Formula II with an acid chloride (RCOCI), acid ester (RCOOR wherein R is methyl or ethyl), or the mixed anhydride of a free acid (RCOOH) and trifluoroacetic acid.  
  The reaction of the compounds of Formula II with an acid chloride (RCOCl) to obtain the carbonylamino compounds of Formula III is carried out in the presence of an organic solvent, e.g., pyridine, acetone, tetrahydrofuran, and the like, at a temperature of from about 40 to 35C. for from about 2 to hours.  
  The reaction of the compound of Formula II with an acid ester (RCOOR to obtain the carbonylamino compounds of Formula [II is carried out at a temperature of from about 100 to 200C. for from about I to 20 hours.  
  The reaction of the compound of Formula II with a mixed anhydride of a free acid (RCOOH) and trifluoroacetic acid, prepared from the free acid and trifluoroacetic acid anhydride, to obtain the carbonylamino compounds of Formula I&#34; is carried out in the presence of an inert organic solvent, e.g., tetrahydrofuran, acetone, and the like, and in the presence of a base, e.g., triethylamine, and the like, at a temperature of from about 20 to C. for from about 1 to 20 hours.  
  The thus-obtained carbonylamino compounds of Formula III, obtained by reaction with an acid chloride, acid ester, or mixed anhydride, as described above, are then converted to the corresponding thionylcarbonylamino compounds of Formula IV by treatment with phosphorous pentasulfide (P 8 in an inert organic solvent, e.g., pyridine, dioxane, and the like, at a temperature of from about 80 to 120C, for from about I to 20 hours.  
 action is carried out using bromine or chlorine, the compounds of Formula l can, if desired, be isolated as their pharmaceutically acceptable hydrobromide or hydrochloride salts, or treated with a base, e.g., ammonia, sodium or potassium bicarbonate and the like, to obtain the corresponding free bases.  
  When the oxidation reaction is carried out using other than bromine or chlorine, the thus-obtained free bases of Formula I can be converted to their pharmaceutically acceptable salts by reaction with pharmaceutically acceptable acids, for example, inorganic acids, e.g., halogen hydroacids (particularly hydrochloric and hydrobromic), nitric acid, phosphoric acids, sulphonic acids, monoand dicarboxylic acids, and the like; and organic acids, e.g., acetic, maleic, succinic, tartaric, lactic, citric, sorbic, salicylic, and the like.  
  Alternatively, the 2-(methylsulfinylphenyl)-I,2,4- thiadiazolo[2,3-a]-benzimidazole compounds of Formula I are obtained by subjecting the corresponding 2- (methylthiophenyl )-l ,2,4-thiadiazolo-[ 2,3-a]- benzimidazole compounds to a further oxidation with an oxidizing agent, e.g., m-chloroperbenzoic acids, peracetic acid, and the like, in the presence of an inert organic solvent, e.g., chloroform, dichloromethane, and the like, at temperatures of from about 30 to 30C. for from one-half to 24 hours.  
  The thus-obtained 2-(methylsulfinylphenyl)-l,2,4- thiadiazolo-[2,3-a]-benzimidazole compounds can then be converted to their pharmaceutically acceptable salts as previously described.  
  The compounds of Formula I, or the pharmaceutically acceptable salts thereof, can be formulated into solutions, creams and ointments, according to methods known to those skilled in the art, for topical administration. Preferably a concentration of from about 0.5 to 5 percent of the active ingredient is used.  
  It is to be understood that isolation of the compounds described herein can be effected by any suitable sepa-. ration or purification procedure, such as, for example, extraction, filtration, evaporation, distillation, crystallization, thin-layer chromatography or column chromatography, or a combination of these procedures lllustrations of suitable separation and isolation procedures can be had by reference to the examples described herein below. However, other equivalent separation or isolation procedures could, of course, also be used.  
  A further understanding of the invention can be had from the following non-limiting examples. Also, where necessary, examples are repeated to provide starting materials for subsequent examples.  
 EXAMPLE 1 A. A solution of 20 g. of Z-aminobenzimidazole (ll) in 150 ml. of pyridine is cooled to 20C. and 20 g. of 3-furoyl chloride is added thereto. The thus-obtained reaction mixture is allowed to warm slowly to between 20 and 30C. (room temperature), and maintained at this temperature for hours, diluted with water and filtered to give a residue which is recrystallized from acetic acid to yield 2-(3-furylcarbonylamino)- benzimidazole [(lll), R 3-furyl].  
  Similarly, substituting a stoichiometric equivalent amount of benzoyl chloride,  
 4-chlor0benzoyl cloride,  
 4-methoxybenzoyl chloride,  
 4-methylbenzoyl chloride,  
 4-methylthiobenzoyl chloride,  
 4-methylsulfinylbenzoyl chloride,  
 4-tert.-butylbenzoyl chloride, 4-trifluoromethylbenzoyl chloride,  
 2 furoyl chloride,  
 Z-naphthoyl chloride,  
 2-thenoyl chloride,  
 3-thenoyl chloride,  
 4-thiazoloyl chloride,  
 S-thiazoloyl chloride,  
 2-methyl-4-thiazoloyl chloride,  
 1,2,3-thiadiazol-4-oyl chloride, and  
  1,2,5-thiadiazol-3-oyl chloride, for 3-furoyl chloride in the procedure of Example 1A is productive of 2-phenylcarbonylamino-benzimidazole 2-(4-chlorophenylcarbonylamino)-benzimidazole 2-(4-methoxyphenylcarbonylamino)-benzimidazole, 2-(4-methylphenylcarbonylamino)-benzimidazole, 2-(4-methylthiophenylcarbonylamino)- benzimidazole, 2-(4-methylsulfinylphenylcarbonylamino)- benzimidazole, 2-(4-tert.-butylphenylcarbonylamino)- benzimidazole, 2-(4-trifluoromethylphenylcarbonylamino)- benzimidazole, 2-(2-furylcarbonylamino)-benzimidazole, 2-(Z-naphthylcarbonylamino)-benzimidazole,  
 2-( Z-thienylcarbonylamino)-benzimidazole,  
 2-(3-thienylcarbonylamino)-benzimidazole,  
 2-(4-thiazolylcarbonylamino)-benzimidazole,  
 2-(S-thiazolylcarbonylamino)-benzimidazole,  
 2-(2-methyl-4-thiazolylcarbonylamino)- benzimidazole, I  
 2-( l,2,3-thiadiazol-4-ylcarbonylamino benzimidazole, and  
 2-( l,2,5-thiadiazol-3-ylcarbonylamino)- benzimidazole, respectively.  
  B. A mixture of 9 g. of Z-aminobenzimidazole (ll) and 10 g. of 3-pyridinecarboxylic acid methyl ester (methyl nicotinate) is heated at l60C. for about 10 hours. The reaction mixture is then triturated with 50 ml. of hot methanol, followed by filtration to yield a residue comprising 2-(3-pyridylcarbonylamino)- benzimidazole [(lll), R 3-pyridyl].  
  Similarly, substituting a stoichiometric equivalent amount of 2-thiazolecarboxylic acid methyl ester,  
 Z-pyridinecarboxylic acid methyl ester, and  
  4-pyridinecarboxylic acid methyl ester for 3 pyridinecarboxylic acid methyl ester in the procedure of Example 1B is productive of 2-(2-thiazolylcarbonylamino)-benzimidazole,  
 2-(Z-pyridylcarbonylamino)-benzimidazole, and  
  2-(4-pyridylcarbonylamino)-benzimidazole, respectively.  
  C. 3.7 G. of 2-pyrazinecarboxylic acid is suspended in 20 ml. of dry tetrahydrofuran and 6.3 g. of trifluoroacetic anhydride is added thereto. To the resulting solution, at 20-25C., there is added 8.5 ml. of triethylamine and 4 g. of 2-aminobenzimidazole (ll) and the thus-obtained reaction mixture is stirred at 20-25C. for about 5 hours. 200 Ml. of water is then added, followed by filtration and the residue is recrystallized from aqueous acetic acid to yield 2-(2-pyrazinylcarbonylamino)-benzimidazole [(III), R 2-pyrazinyl].  
  Similarly, substituting a stoichiometric equivalent amount of 3-isothiazolecarboxylic acid,  
 4-isothiazolecarboxylic acid, and  
  5-isothiazolecarboxylic acid, for Z-pyrazinecarboxylic acid in the procedure of Example IC is productive of 2-(3-isothiazolylcarbonylamino)-benzimidazole,  
 2-(4-isothiazolylcarbonylamino)-benzimidazole, and  
  2-(5-isothiazolylcarbonylamino)-benzimidazole, respectively.  
 EXAMPLE 2 To l0 g. of 2-(3-furylcarbonylamino)-benzimidazole [(III), R 3-furyl] in 200 ml. of pyridine is added 10 g. of phosphorous pentasulfide and the reaction mixture is heated to l00-l 10C. for 10 hours. The bulk of the pyridine is removed under vacuum and the residue is treated with 500 ml. of saturated potassium bicarbonate solution, filtered and recrystallized from methanol-chloroform to yield 2-( 3-furylthiocarbonylamino)-benzimidazole [(lV), R 3-furyl].  
  Similarly, substituting a stoichiometric equivalent amount of the other compounds obtained in Example 1A; the compounds obtained in Example 1B; and the compounds obtained in Example 1C; for 2-(3-furylcarbonylamino)-benzimidazole, and following the procedure of Example 2 is productive of 2-phenylthiocarbonylamino-benzimidazole,  
 2-(4-chlorophenylthiocarbonylamino)- benzimidazole,  
 2-(4-methoxyphenylthiocarbonylamino)- benzimidazole,  
 2-(4-methylphenylthiocarbonylamino)- benzimidazole,  
 2-(4-methylthiophenylthiocarbonylamino)- benzimidazole,  
  Similarly, substituting a stoichiometric equivalent R amount of 2-( 2-pyridylthiocarbonylamino S benzimidazole for 2-(2-pyrazinylthiocarbonylamino)- N/ I benzimidazole in the procedure of Example 3B is productive of 2-(2-pyridyl)-l,2,4-thiadiazolo-[2,3-a]- benzimidazole. N  
 C. To 0.28 g. 2-(4-methylthiophenyl)-l,2,4-  
 thiadiazolo-benzimidazole [(l), R 4- I methylthiophenyl] in 250 ml. of chloroform and 5 ml.  
 of methanol at 20C. is added 0.2 g. of mchloroperbenzoic acid in ml. of chloroform. The rewherein R is and action mixture is allowed to stand at 2025C. for 5 in which R and R are hydrogen, lower alkoxy, halo,  
 hours, washed with 20 ml. of dilute sodium bicarbonate nitro, lower alkyl, lower alkylthio, lower alkylsulfisolution, 20 ml. of water and dried over magnesium sulnyl, or trifluoromethyl;  
 fate, The chloroform solution is concentrated and the R is hydrogen, lower alkoxy, halo, nitro, or lower alresidue remaining is recrystallized from methanolkyl;  
 chloroform to yield 2-(4-methylsulfinylphenyl)-l,2,4- and the pharmaceutically acceptable salts thereof.  
 thiadiazolo-[2,3-al-benzimidazole. 2. A compound of claim 1 wherein R is phenyl, 4-  
 In the Examples above, specific reaction sequences p y yp y y p y have been extended, in a general sense, to the preparamethylthiophenyh y p y 44cm tion of other similar and related compounds. It should y p y f y l y &#39;y Y be understood, however, that with respect to any comp yL 2411181134 and y pound which has been prepared by the extension of a The compound of Claim 2 wherein R is P y specific reaction sequence, it may be necessary or dey &#39;l sirable to utilize solvents, reaction media. recrystalli- The compound of Claim 2 wherein R is zation media, reaction times or temperatures, etc.. chlorophenyl, &#39;P y other than the ones given in the specific reaction se- 45 quence upon which such extension is based. Addition- The compound of Claim 2 wherein R is ally, the specific reaction sequence or manner in which yp y yp yh- 1 2.  
 particular compounds are to be prepared will depend, thifldiaZOlO-ll3-al-benlimidaloleinter alia, upon the availability of the necessary starting 6. The compound of claim 2 wherein R is 4- materials, or the ease in which the desired starting mamethylphenyl, 2-(4-methylphenyl)-l,2,4-thiadiazoloterials can be prepared, and the reactivity thereof. [2,3-a1-benzimidazole.  
 These variations are deemed to be within the skill of 7. The compound of claim 2 wherein R is 4- those working in this art and will be apparent from a methylthiophenyl, 2-(4-methylthiophenyl)-l,2,4-  
 consideration of the particular reactants utilized and/or thiadiazolo-[ 2,3-a]-benzimidazole.  
 particular compound desired to be produced. 8. The compound of claim 2 wherein R is 4-methyl- While the present invention has been described with ulfinylphenyl, 2-(4-methylsulfinylphenyl)-l,2,4-  
 reference to specific embodiments thereof, it should be thifldia20l0-l23-a]-benZimidaZ0l6- understood by those skilled in this art that various 9. The compound of claim 2 wherein R is 4-tert.-  
 changes may be made and equivalents may be substibutylphenyl, 2-(4-tert.-butylphenyl)-l,2,4-thiadiazolotuted without departing from the true spirit and scope [2,3-a]-benzimidazole.  
 of the invention. In addition. many modifications may 10. The compound of claim 2 wherein R is 4-tribe made to adapt a particular situation, material or fluoromethylphenyl, 2-(4-trifluoromethylphenyl)- composition of matter, process, process step or steps, l,2,4-thiadiazolo-[2,3-a]-benzimidazole.  
 or then-present objective to the spirit of this invention 11. The compound of claim 2 wherein R is 2-furyl,  
 without departing from its essential teachings. 2-(2-furyl)-l,2,4-thiadiazolo-[2,3-a]-benzimidazole.  
 What is claimed is: 12. The compound of claim 2 wherein R is 3-furyl,  
 l. A compound represented by the formula 2-(3-furyl)-l ,2,4-thiadiazolo-[2,3-a]-benzimidazole.  
  13. The compound of claim 2 wherein R is 2- 2-(2-thienyl)-l ,2,4-thiudiazolo-[2.3-a]-benzimidazole. naphthyl, 2-(2-naphthyl)-l,2 4-thiadiazolo-[2,3-a]- 15. The compound of claim 2 wherein R is 3-thienyl benzimidazolei 2-( 3-thienyl)- l ,2 4-thiadiazolo-[ 2,3-al-benzimidazole.  
 14. The compound of claim 2 wherein R is 2-thienyl,  
  UNITED STATES PATENT OFFICE W C R c T (:0 c ION Patent No. 3&#39;880&#39;874 Dated Ap il 29, 1975 Inventor) Col1n C. Beard It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:  
  Column 2, line 17, Amonst should read Amongst and &#34;Amongst&#34; should read fungi Column 5, line 29, &#34;cloride&#34; should read chloride Column 7, line 33, &#34;furly&#34; should read furyl Column 10, Claim 1, line 0 30, &#34;are hydrogen&#34; should read are each hydrogen Signed and Scaled this eleve th 3 0 [SEAL] D y f May 1976 Arrest:  
  RUTH. C. M:ASON C. MARSHALL DANN I Q 1 (mnmissimu&#39;r ()fl&#39;algnfs j Trademark-X