Transition-Metal-Free Decarboxylative Propargylic Substitution/Cyclization with either Azolium Enolates or Acyl Anions.

Presented herein is an unprecedented transition-metal-free propargylic substitution reaction with either azolium enolates or acyl anions, which are generated from aldehydes under N-heterocyclic carbene catalysis. This new catalytic activation operates on readily available cyclic propargylic carbamates through decarboxylation, and generates reactive allene intermediates that can undergo divergent cyclization pathways to deliver skeletally diverse polycyclic compounds with high levels of efficiency and excellent enantioselectivities.