TRICHLOROMETHYLATION REACTION .3. REACTION WITH BENZOIC ANHYDRIDE AND PARTICIPATION BY SOLVENT 1,2-DIMETHOXYETHANE

Reaction of sodium trichloroacetate with benzoic anhydride in dimethoxyethane (DME) solution yields C6H5COOC(═CCl2)C6H6 (1, 79%), benzoic acid, some methyl benzoate, and minor amounts of α,α,α-trichloro-, α, α-dichloro-, and α-chloroacetophenone. A similar reaction with p,p′-dichlorobenzoic anhydride gives the corresponding p,p′-dichloro analog (2) of 1, methyl p-chlorobenzoate, and the p-chloro analogs of the other minor components. The reaction of sodium trichloroacetate with α, α, α-trichloroacetophenone and p,p′-dichlorobenzoic anhydride in DME produces p-ClC6H4COOC(═CCl2)C6H5 (3). The proposed mechanism for the formation of 1, 2, and 3 involves the abstraction of chlorine from α,α, α-trichloroacetophenone, initially produced by a normal trichloromethylation reaction, followed by a condensation of the enolate anion with the parent anhydride. The methyl benzoate originates from the DME solvent. Reaction of sodium trichloroacetate, α,α,α-trichloroacetophenone, and DME also gives methyl benzoate. Reaction of DME with various bases produces formaldehyde and ethylene. These results are accounted for by a mechanism involving the abstraction of a proton from the methyl group of DME and a resulting decomposition of the DME. The methoxide ion produced in the decomposition then attacks the trichloroacetophenone to give methyl benzoate. © 1968, American Chemical Society. All rights reserved.