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Stereodivergency of Triazolium and Imidazolium-Derived NHCs for Catalytic, Enantioselective Cyclopentane Synthesis

2009; American Chemical Society; Volume: 11; Issue: 3 Linguagem: Inglês

10.1021/ol802739d

1523-7060

Juthanat Kaeobamrung, Jeffrey W. Bode,

Coordination Chemistry and Organometallics

Chiral triazolium- and imidazolium-derived N-heterocyclic carbene catalysts promote the direct annulation of alpha,beta-unsaturated aldehydes and achiral alpha-hydroxy enones to afford cyclopentane-fused lactones with high enantioselectivity. Remarkably, otherwise structurally identical imidazolium and triazolium precatalysts afford different major products. These studies provide both an efficient entry to valuable chiral structures and a dramatic demonstration of stereodivergency of chiral imidazolium versus triazolium-derived N-heterocyclic carbene catalysts.