Efficient assembly of polysubstituted pyrroles via a (3 + 2) cycloaddition/skeletal rearrangement/redox isomerization cascade reaction.

An unprecedented cascade strategy, used in conjunction with a redox isomerization, for the synthesis of 3-allyl pyrroles is reported. In a single step, readily accessible simple starting materials are transformed into highly substituted pyrroles with high efficiency. The products obtained contain allyl substituents, which can be readily elaborated to other useful functional groups. The reaction proceeds through an unusual (3 + 2) cycloaddition/skeletal rearrangement/redox isomerization pathway.