Stereodivergency of Triazolium and Imidazolium-Derived NHCs for Catalytic, Enantioselective Cyclopentane Synthesis
journal contributionposted on 05.02.2009 by Juthanat Kaeobamrung, Jeffrey W. Bode
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Chiral triazolium- and imidazolium-derived N-heterocyclic carbene catalysts promote the direct annulation of α,β-unsaturated aldehydes and achiral α-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.