On the Dual Role of N-Heterocyclic Carbenes as Bases and Nucleophiles in Reactions with Organic Halides

Abstract

The synthetic consequences of different basicities, nucleophilicities, and sterics of N-heterocyclic carbenes have been studied in reactions of imidazolin-2-ylidenes with organic halides. Highly nucleophilic and less basic carbenes cleanly gave alkyli­deneimidazolines, the deoxy analogues of Breslow-type intermediates. More basic NHCs engaged in unwanted deprotonation or dehydrohalogenation reactions.

N-heterocyclic carbenes - enamines - umpolung - imidazoles - nucleophilicity

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