Based on our recent finding that 2,6-dimethoxyphenyl-substitutedNHCs show superior reactivity in the hydroacylation reactions of electron-neutral olefins compared with known NHCs, we now report the syntheses and crystal structures of four highlyelectron-rich2,6-dimethoxyphenyl-substitutedNHCs and show the increase in efficiency caused by the electron-rich aryl substituent in hydroacylation reactions
N-Heterocyclic Carbene-Catalyzed Hydroacylation of Unactivated Double Bonds
作者:Keiichi Hirano、Akkattu T. Biju、Isabel Piel、Frank Glorius
DOI:10.1021/ja906361g
日期:2009.10.14
An intramolecular N-heterocyclic carbene (NHC)-catalyzed hydroacylation of unactivated double bonds is reported. Systematic variation of the catalyst structure revealed an N-mesitylthiazolylidene annulated with a seven-membered ring to be especially reactive. This NHC enables a unique C-C bond-forming reaction to afford substituted chroman-4-ones in moderate to excellent yields, even ones containing all-carbon quaternary centers.
Carboranes as Aryl Mimetics in Catalysis: A Highly Active Zwitterionic NHC-Precatalyst
and control reactions. In the design of Nheterocycliccarbene catalysts both electronic and steric nature of the nitrogen substituents play a crucial role. While hydrocarbon-based systems and especially aryl residues have considerably contributed to surmount multifaceted catalytic challenges, the unique properties of carborane moieties such as delocalized charge, potential planar chirality and their