Cyclization of 1,6-Enynes Catalyzed by Gold Nanoparticles Supported on TiO<sub>2</sub>: Significant Changes in Selectivity and Mechanism, as Compared to Homogeneous Au-Catalysis
作者:Charis Gryparis、Christina Efe、Christos Raptis、Ioannis N. Lykakis、Manolis Stratakis
DOI:10.1021/ol301212j
日期:2012.6.15
Gold nanoparticles supported on TiO2 (1.2 mol %) catalyze, for the first time under heterogeneous conditions, the cycloisomerization of a series of 1,6-enynes in high yields. In several cases, the product selectivity differs significantly as compared to homogeneous Au(I)-catalysis. Based on product analysis and stereoisotopic studies it is proposed that the major or exclusive pathway involves a 5-exo cyclization mode to form stereoselectively gold cyclopropyl carbenes that undergo a single cleavage pathway, in contrast to homogeneous Au-catalysis where the double cleavage pathway operates substantially.