Active Low-Valent Niobium Catalysts from NbCl₅ and Hydrosilanes for Selective Intermolecular Cycloadditions

Abstract

An active niobium catalyst was developed via a simple and nontoxic reduction method from NbCl(5)/hydrosilane and utilized for the selective [2 + 2 + 2] cycloaddition reaction of terminal alkynes and alkenes/α,ω-dienes, to give 1,3-cyclohexadiene derivatives in high yields with excellent chemo- and regioselectivity.