Isolation of Cyclopropenylidene–Lithium Adducts: The Weiss–Yoshida Reagent

Abstract

Luck is important: In the 1970s, Yoshida and Weiss both had the right cyclopropenium cation precursor. With the right counteranion, they would have isolated the first carbene–lithium adduct (see scheme; C black, N blue, O red, Li pink, B yellow, F green). With the right base and counteranion combination, they would have isolated the first stable free carbene.