Synthesis Of 1,2- And 1,3-dicarboxylic Acids Via Pd(ii)-catalyzed Carboxylation Of Aryl And Vinyl C-h Bonds

摘要

Pd(0)-catalyzed Heck carbonylation of aryl halides, triflates, and tosylates is an expedient route to access carboxylic acid derivatives. Direct conversion of aryl and alkyl C-H bonds by Pd(II) catalysts into carboxylic acids using excess arenes and alkanes in trifluoroacetic acid has been reported by Fujiwara.Orito developed an alkylamine-directed regioselective carbonylation of aryl C-H bonds to prepare benzolactams using the substrate as the limiting reagent. Recently, an intriguing ortho-ethoxycarbonylation of 2-phenylpyridines using diethyl azodicarboxylate as the carboxyl donor was reported. Herein, we disclose a new carboxylation reaction of broadly useful aryl and vinyl carboxylic acids using a C-H activation/CO insertion sequence. This protocol provides a method for the preparation of dicarboxylic acids which is complementary to the ortho-lithiation/CO_2 insertion process directed by amide groups. We have also characterized by X-ray crystallography the first C-H insertion intermediate from the cyclometalation of carboxylic acids.