Oxygen transposition of formamide to α-aminoketone moiety in a carbene-initiated domino reaction.

Abstract

The carbonyl group is one of the most important functional groups in organic chemistry. C=O cleavage and full transfer of the resulting fragments into final products would be extremely attractive and open up new avenues in retrosynthetic planning. In this context, as an N-containing carbonyl compound, the transformations of formamides, wherein C=O cleavage occurring with simultaneous incorporation of 'O' and aminomethine moieties to highly functionalized amines, remain a formidable challenge. Here we disclosed a dirhodium/Xantphos or dirhodium-palladium dual catalysed reaction of diazo compounds and allylic substrates in dimethyl formamide, giving various α-aminoketones and cyclopentenone derivatives efficiently featured with extensively reorganized structure, wherein a carbenic carbon was formally inserted into C=O bond and α-group of the carbene was shifted to the residual aminomethine moiety. Mechanistic studies revealed that three or six domino steps are involved in this catalytic process, including epoxidation, dyotropic type rearrangement, allylic alkylation, Claisen rearrangement, isomerization and Nazarov cyclization.