Intemiolecular and Selective Synthesis of 2,4,5-Trisubstituted Oxazoles by a Gold-Catalyzed Formal [3 + 2] Cycloaddition

摘要

The generation and subsequent evolution of metal-stabilized carbocation/carbenoid reactivity patterns from C—C π systems is central to π-acid catalysis. Following the formation of α-oxo/imido organogold species by intramolecular atom-transfer processes onto alkynes, such intermediates [Eq. (1), B-D, Ts = toluene-4-sulfonyl] have very recently been accessed by intermolecular attack of an O- or N-nucleophilic oxidant or nitrene equivalent to an electro-philically activated π system [Eq. (1), A→B].