Coarctate cyclization reactions: a primer

Abstract

The cleavage of five-membered heterocycles possessing an exocyclic carbene or nitrene to form conjugated ene–ene–yne systems has been documented for over 40 years; however, the reverse reaction, using a conjugated “ene–ene–yne” precursor to form a heterocycle is a relatively new approach. Over the past decade, the Haley and Herges groups have studied computationally and experimentally the cyclization of the “hetero-ene–ene–yne” motif via an unusual class of concerted reactions known as coarctate reactions. This feature article details our synthetic and mechanistic work involving triazene–arene–alkynes and structurally-related systems to generate heterocycles using coarctate chemistry.