Lewis acid-catalyzed reactions of ethyl diazoacetate with aldehydes. Synthesis of α-formyl esters by a sequence of aldol reaction and 1,2- nucleophilic rearrangement

Article abstract of DOI:10.1016/S0040-4039(99)00932-6

Ethyl diazoacetate reacts with a variety of aldehydes in the presence of a Lewis acid catalyst to give either β-keto esters or α-formyl esters, the types of products mainly depending upon the nature of Lewis acid catalysts employed. Reactions catalyzed by Lewis acids such as SnCl₂ and SnCl₄ provide β-keto esters via nucleophilic 1,2-hydride migration, while those catalyzed by trimethylsilyl triflate give α-formyl esters via migration of the substituent of the aldehyde. Reaction mechanisms are discussed.