New frontiers of N-heterocyclic carbene catalysis

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N-heterocyclic carbene(NHC)is both a family of strongσ-donor ligands for transition metals and a privileged class of organocatalysts with synthetic potential that rivals popular amine and phosphoric acid catalysts.NHC was found as a key catalytic species in thiamine diphosphate catalyzed biochemical reactions[1].However,due to their inherent chemical instability,free NHCs had not been isolated until1991 by Ardungo et al.[2].Since then,the use of chiral N-heterocyclic carbene (NHC) is a family of strong sigma-donor ligands for transition metals and a privileged class of organocatalysts with synthetic potential that rivals popular amine and phosphoric acid catalysts. NHC found as a key catalytic species in thiamine diphobic catalyzed biochemical reactions [1] .However, due to their inherent chemical instability, free NHCs had not been isolated until1991 by Ardungo et al. [2] .Since then, the use of chiral
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