Superelectrophilic Fe(III)–Ion Pairs as Stronger Lewis Acid Catalysts for (<i>E</i>)-Selective Intermolecular Carbonyl–Olefin Metathesis

Abstract

An intermolecular carbonyl-olefin metathesis reaction is described that relies on superelectrophilic Fe(III)-based ion pairs as stronger Lewis acid catalysts. This new catalytic system enables selective access to (<i>E</i>)-olefins as carbonyl-olefin metathesis products. Mechanistic investigations suggest the regioselective formation and stereospecific fragmentation of intermediate oxetanes to be the origin of this selectivity. The optimized conditions are general for a variety of aryl aldehydes and trisubstituted olefins and are demonstrated for 28 examples in up to 64% overall yield.