Amides as surrogates of aldehydes for C-C bond formation: amide-based direct Knoevenagel-type condensation reaction and related reactions

Aldehydes are perhaps the most versatile compounds that enable many C-C bond forming reactions, which are not amenable for other subclasses of carbonyl compounds. We report the first use of amides as surrogates of aldehydes for C-C bond formation, namely, the direct Knoevenagel-type condensation based on amides. The one-pot method consists of controlled reduction of an amide with LDBIPA [LiAlH(iBu)(2)(OiPr)], Lewis acid-mediated release of a reactive iminium ion intermediate, nucleophilic addition, and in situ elimination of amine. The reaction shows good functional group tolerance. We also demonstrated that the Schwartz reagent could be used as an alternative of LDBIPA. The employment of nitromethane and a silyl enol ether as the nucleophiles opens an avenue for the unprecedented amide-based nitro-aldol condensation reaction and aldol condensation reaction, respectively.