Spiro-fused six-membered N-heterocyclic carbene: a new scaffold toward unique properties and activities

Abstract

A six-membered N-heterocyclic carbene fused with a spiro-scaffold is designed. The new NHC shows stronger σ-donation ability than typical 5-membered NHCs. This property leads to interesting reactivities of this spiro-fused six-membered NHC. For example, the NHC–BF₃ Lewis pair complex can be readily prepared by using LiBF₄ as the BF₃ source, or through a direct bond-reconstruction of the tetrafluoroborate salt NHC·HBF₄.