3,4-Dichlorobenzoic acid → 3,4-Dichloro-2-methylbenzoic acid

Reaction equation

[CH2:1]([Li])CCC.[Cl:6][C:7]1[CH:8]=[C:9]([CH:13]=[CH:14][C:15]=1[Cl:16])[C:10]([OH:12])=[O:11].CI>O1CCCC1>[Cl:6][C:7]1[C:8]([CH3:1])=[C:9]([CH:13]=[CH:14][C:15]=1[Cl:16])[C:10]([OH:12])=[O:11]

Participants

Procedure

n-Butyl lithium (2.5M in hexanes, 180 ml) was added during 1 hour to a stirred solution of 3,4-dichlorobenzoic acid (40.0 g) at -78° C. and stirring maintained at that temperature overnight. A solution of methyl iodide (72 ml) in tetrahydrofuran was then added during 1.5 hours and the mixture kept at -78° C. for 3 hours and allowed to warm to room temperature overnight. The solvent was evaporated and the mixture added to water, acidified (concentrated hydrochloric acid) and extracted (ethyl acetate). The extract was dried (magnesium sulphate), evaporated and triturated (ether) to give 3,4-dichloro-2-methylbenzoic acid (33.3 g) as a white solid, m.p. 177°-178° C.