Open-Vessel Microwave-Mediated (2+2+2)-Cyclotrimerization Reactions

摘要

[2+2+2]-Cyclotrimerization reactions often suffer from low reaction rates and low chemoselectivity. We are reporting a solution to both problems through the use of open-vessel conditions for microwave-mediated cyclotrimerization reactions. The transition-metal-catalyzed [2+2+2]-cyclotrimerization reaction of alkynes, nitriles, isocyanates, carbodiim-ides and other reaction partners is a versatile tool for the synthesis of aromatic carbo- and heterocyclic structures, and several applications of this methodology in the synthesis of natural products have been reported. The most commonly used catalysts for [2+2+2]-cyclotrimerization reactions are based on Co, Ni, Rh, and Ru. Typically, a specific catalyst (metal and ligand) is selected for a cyclotrimerization reaction of a specific substrate.