Asymmetric [2+2] photocycloaddition <i>via</i> charge transfer complex for the synthesis of tricyclic chiral ethers
作者:Ana M. Martínez-Gualda、Pablo Domingo-Legarda、Thomas Rigotti、Sergio Díaz-Tendero、Alberto Fraile、José Alemán
DOI:10.1039/d1cc00035g
日期:——
The asymmetricsynthesis of chiral polycyclic ethers by an intramolecular [2+2] photocycloaddition is described. This process proceeded through a photocatalytically active iminium ion-based charge transfer (CT) complex under visible light irradiation. In this way a stereocontrolled [2+2] photocycloaddition is enabled leading to tricyclic products with good enantiomeric ratios.
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.