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.