Process for preparing 3-alkyl-5-t-butylphenols
.United States Patent 1 Kamoshita et al.  
 [451 Apr. 29, 1975 1 PROCESS FOR PREPARING 3-ALKYL-5-T-BUTYLPHENOLS [75] Inventors: Katsuzo Kamoshita, Toyonaka;  
 Shinji Nakai, Takarazuka, both of Japan [73] Assignee: Sumitomo Chemical Company,  
 Limited, Osaka-shi, Japan [22] 1 Filed: Apr. 13, 1971 [21] 7 Appl. No.: 133,754  
 [30] Foreign Application Priority Data Apr. 15, 1970 Japan 45-32558 [52] 11.8. CI 260/624 E; 260/621 E [51] Int. Cl. C07c 39/06 [58] Field of Search 260/624 E, 624 C, 621 E [56] References Cited UNITED STATES PATENTS 2,107,060 2/1938 Olin 260/621 E 3,014,079 12/1961 Olin 260/624 FOREIGN PATENTS OR APPLICATIONS 555,751 9/1943 United Kingdom 260/621 E 1,112,502 5/1968 United Kingdom 260/621 E OTHER PUBLICATIONS Elder et al., Canadian J. of Chem,&#34; Vol. 41, pp. 1653-1656, July 1963, No. 7. Braddeley, .Chem. Soc. Jour., (1943), pp. 527-531.  
 Primary ExaminerBernard Helfin Assistant ExaminerW. B. Lone Attorney, Agent, or Firm-Craig &amp; Antonelli 4 Claims, No Drawings PROCESS FOR PREPARING 3-ALKYL-5 -T-BUTYLPHENOLS The present invention relates to a process for preparing 3-alkyl-5-t-butylphenols. More particularly, it is concerned with a process for preparing 3-alkyl-5-tbutylphenols in high yields which comprises contacting 3-alkyl-6-t-butylphenols with aluminum chloride under a mild condition to rearrange the t-butyl group at the 6-position to the 5-position, the alkyl being an alkyl having 1 to 3 carbon atoms.  
  For alkylation of m-cresol, there has heretofore been adopted a procedure where it is reacted with an alkylating agent such as an alkanol, an olefin or an alkyl halide in the presence of a catalyst such as a strong acid or a Fridel-Crafts type catalyst. In this procedure, an alkyl group is selectively introduced into the oor p-position of the phenolic OH group on the benzene ring and the introduction of an alkyl group into the m-position hardly takes place. Thus, the industrial production of 3-alkyl-5-t-butylphenols in a single step by the utilization of the said procedure is hardly possible.  
  On the other hand, it is known that m-alkylphenols can be produced by heating the corresponding oor palkylphenols above 125C in the presence of a strong acid and a natural or synthetic alumina-silicate to rearrange the alkyl group at the oor p-position to the mposition [U.S. Pat. No. 3,014,079]. When this procedure is applied to 3-alkyl-6-t-butylphenols, however, the elimination of the t-butyl group preferentially takes place rather than the rearrangement of the t-butyl group so that 3-alkyl-5-t-butylphenols are obtained only in trace.  
  As the results of the extensive study, it has now been found that the treatment of 3-alkyl-6-t-butylphenols with aluminum chloride under a mild condition affords 3-alkyl-5-t-butylphenols in excellent yields. In this connection, it should be noted that the above rearrangement is quite specific to 3-alkyl-6-t-butylphenols and not applicable to any other similar or analogous compound. For instance, the application to 3-methyl-6- isopropylphenol or 3-methyl-6-ethylphenol results only in the recovery of the starting compound without the proceeding of the rearrangement. Further, for instance, the application to o-t-butylphenol gives p-t-butylphenol in a high yield with no material production of the corresponding m-isomer. The application to 2-t-butyl-4- methylphenol results in the elimination of the t-butyl group to give p-cresol. In case of the application to 3-methyl-4-t-butylphenol, the rearrangement of the tbutyl group to the m-position does not take place. The present invention is based on the said finding.  
  According to the present invention, 3-alkyl-6-tbutylphenols are treated with aluminum chloride at a temperature below 70C, preferably of to 30C while stirring for 2 to 4 hours at atmospheric pressure whereby the rearrangement of the t-butyl group at the 6-position to the -position takes place to give 3-alkyl- S-t-butylphenols. The amount of aluminum chloride to be used may be 0.25 to 2 mol, preferably 1 mol, per mol of the starting phenol.  
  The thus obtained 3-alkyl-5-t-butylphenols are utilizable as intermediates in the production of various per se useful substances. For instance, the reaction with methyl isocyanate affords 3-alkyl-5-t-butylphenol N- methylcarbamates, which are insecticides exerting a strong controlling activity against various harmful insects without any toxicity to mammals.  
  Practical and presently preferred embodiments of the present invention are illustratively shown in the following Examples.  
 EXAMPLE 1 Material Percent (7() (l) m-Cresol 21.0 (ll) Unidentified component l) 2.3 (III) Unidentified component (2) 0.9 (W) 3-Methyl-5-t-butylphenol 67.0 (V) High boiling component 8.8  
  Elementrary analysis of the distilled fraction ((IV): Calculated (for C H O): C, 80.42 H, 9.84 Found: C, 80.62 H, 9.58  
 EXAMPLE 2 3-Methyl-6-t-butylphenol (30 g) and powdery anhydrous aluminum chloride (7 g) are reacted in the same manner as in Example 1. The produced oily material is fractionally distilled to give 3-methyl-5-t-butylphenol as a fraction boiling at to l04C/2.5 mmHg.  
 The oily product before fractional distillation is con- 8 firmed to have the following composition by gas chromatography:  
 Material Percent (92) (l) m-Cresol 35.2  
 (11) Unidentified component (1) 8.7  
 ([11) Unidentified component (2) 0.5  
 (1V) 3-Methyl-5-t-butylphenol 48.3  
 (V) High boiling component 7.3  
 Elementary analysis of the distilled fraction (1V):  
 Calculated (for C H O): C, 80.42 H, 9.84  
 Found: C, 80.77 H, 9.60  
 EXAMPLE 3 3-Ethyl-6-t-butylphenol (44 g) and powdery anhydrous aluminum chloride (26 g) are reacted in the same manner as in Example 1. The produced oily material is fractionally distilled to give 3-ethyl-5-tbutylphenol as a fraction boiling at to l29C/l.8 mmHg.  
  The oily product before fractional distillation to confirmed to have the following composition by gas chromatography:  
 Material Percent (7r) (1) 3-Ethylphenol 36.3 (ll) Unidentified component (1 4.8 (III) Unidentified component (2) 0.2 (1V) Unidentified component (3) 0.2 (V) 3-Ethyl5-t-butylphenol 31 .3 (V1) High boiling component 27.0  
  Elementary analysis of the distilled fraction (V): Calculated (for C H, O):C, 80.83 H, 10.20 Found: C, 81.22 H, 10.12  
 EXAMPLE 4 Mate rial Percent (71 (l) 3-lsopropylphcnol 3 1.5 ([1) Unidentified component l 1.8 (111) Unidentified component (2) 0.3 (1V) Unidentified component (3) 0.3 (V) 3-lsopropyl-5t-butylphenol 25.6 (V1) High boiling component 40.5  
  Elementary analysis of the distilled fraction (V): Calculated (for G l-I 0): C, 81.18 H, 10.50 Found: C, 81.66 H, 10.05  
 What is claimed is:  
  1. A process for preparing a 3-alkyl-5-t-butylphenol which comprises contacting a 3-alkyl-6-t-butylphenol with aluminum chloride at a temperature between about 0 and 30C to rearrange the t-butyl group at the 6-position to the 5-position, the alkyl group having 1 to 3 carbon atoms.  
  2. The process according to claim 1, wherein the aluminum chloride is anhydrous.  
  3. The process according to claim 1, wherein the contact is effected using a 0.25 to 2 molar amount of aluminum chloride per one molar amount of the 3-alkyl-6-t-butylphenol.  
 4. The process according to claim 1, wherein the contact is effected for 2 to 4 hours.