Synthesis of cyclopent-2-enones through stepwise [3 + 2] cycloaddition of simple silyl enol ethers and alk-1-ynes

Abstract

Treatment of silyl enol ethers and alk-1-ynes with SnCl₄–Bu₃N reagent followed by DBU, leads to cyclopent-2-enones, through [3 + 2] cycloaddition reactions; the initial carbon–carbon bond formation is carbometallation of alkynes, and the second step is a base-promoted intramolecular alkylation which reductively eliminates tin species (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene).