Cyclization of 1,6-enynes catalyzed by gold nanoparticles supported on TiO2: significant changes in selectivity and mechanism, as compared to homogeneous Au-catalysis.
Gold nanoparticles supported on TiO(2) (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.
Department of Chemistry, University of Crete, Voutes 71003 Iraklion, Greece.
Charis
C
Gryparis
Christina
C
Efe
Christos
C
Raptis
Ioannis N
IN
Lykakis
Manolis
M
Stratakis