Bisguanidinium-catalyzed remote enantioselective desymmetrization with 1,2-acyl shift

In this work, we described a remote desymmetrization reaction in which cesium carboxylate, in the presence of bisguanidinium as catalyst, was added to (cis)-α,α′-dibromocyclohexanone to access 6-oxocyclohex-1-enyl ester via a 1,2-acyl shift in a highly enantioselective fashion. In this process, the carboxylate initiated a nucleophilic attack, and then a keto-enol tautomerism led to a 1,2-acyl shift to the neighboring alcohol. Key intermediates were isolated and determined using single-crystal X-ray crystallography. The remote desymmetrization that includes stepwise SN2 and intramolecular acyl transfer was proposed and was further supported using computational studies. Finally, it was successfully applied to a tropinone derivative, realizing carbonyl chain walking efficiently.