Accept it! Although the π‐acceptor properties of N‐heterocyclic carbenes (NHCs) are often considered negligible, they can be enhanced to the extent that they start to dominate the catalytic behavior of gold–NHC complexes (see scheme). As it seems to be easier to tune the π acidity of NHCs than to alter their σ‐donor properties, the general perception of this important class of ancillary ligands needs
Gold(I)-Catalyzed Divergence in the Reactivity of 3-Silyloxy 1,6-Enynes: Pinacol-Terminated vs Claisen-Terminated Cyclization Cascades
作者:Baburaj Baskar、Hyo J. Bae、Sang E. An、Jae Y. Cheong、Young H. Rhee、Alexander Duschek、Stefan F. Kirsch
DOI:10.1021/ol8008733
日期:2008.6.1
On activation with catalytic amounts of gold(I) complexes, 3-silyloxy 1,6-enynes can react through two alternative pathways. In one, a cascade reaction consisting of carbocyclization and subsequent pinacol rearrangement takes place. In the second pathway, a heterocyclization is followed by a Claisen rearrangement. The reaction outcome differs depending on the substitution pattern of the 3-silyloxy 1,6-enynes and, more importantly, the electronic properties of the gold-bound phosphane ligand.