Cobalt-Catalyzed Asymmetric Addition of Silylacetylenes to 1,1-Disubstituted Allenes
摘要:
The asymmetric addition of silylacetylenes to 1,1-disubstituted allenes proceeded in the presence of a cobalt/chiral bisphosphine ligand to give the corresponding enynes with high enantioselectivity. The results of deuterium-labeling experiments indicated that a hydrogen atom at the chiral center is originated from the terminal alkyne, and they were in good agreement with the proposed catalytic cycle where enantioselectivity is determined by the reaction of the proposed pi-allylcobalt intermediate with the terminal alkyne.
Divergent Outcomes of Gold(I)-Catalyzed Indole Additions to 3,3-Disubstituted Cyclopropenes
摘要:
Depending on the conditions employed, gold(I)-catalyzed addition of indoles to 3,3-disubstituted cyclopropenes can be controlled to yield either 3-(E)-vinylindoles (3) or bis-indolylalkanes (4). If the cyclopropene substituents are sterically bulky, unprecedented gold-catalyzed oxidation under air occurs to yield bis-indolylalkene (5) and epoxide (6) at room temperature.