高周期14族元素低配位化合物が触媒する高選択的アルキン三量化反応の発見

抄録

Academically and industrially, the catalytic activation of neutral small molecules followed by the formation of C-C bonds is a highly important method to increase the complexity and/or value of simple starting materials. Traditionally, transition-metal catalysts have been used for this purpose, and these are still considered superior to catalysts based on main-group elements. However, catalytic transformation reactions of neutral small organic molecules in the absence of a transition-metal catalyst remain largely unknown, although such “transition-metal-free” catalytic systems would be highly desirable in order to avoid the use of precious metals. Herein, we will reported the isolation of the stable digermyne with a Ge-Ge triple bond, and demonstrated its high susceptibility to [2+2+2]cycloadditions in the presence of two molecules of alkynes to afford the corresponding 1,2-digermabenzenes. We have since discovered that the reaction of the digermyne with three equivalents of an arylacetylene exclusively affords the corresponding 1,2,4-triarylbenzene derivatives. Finally, we were able to demonstrate that a substoichiometric amount of the digermyne promotes the regioselective cyclotrimerization of several arylacetylenes in high yield. Our results demonstrate that bespoke main-group-element compounds can catalytically activate small neutral organic molecules and induce the formation of C-C bonds. The development of such main-group-element catalysts should represent a highly attractive addition to the toolkit of catalytic coupling reactions, and hopefully improve catalytic efficiency and selectivity under concomitant reduction of the consumption of precious-metal resources.