Copper(I)−Homoscorpionate Catalysts for the Preferential, Kinetically Controlled Cis Cyclopropanation of α-Olefins with Ethyl Diazoacetate
- 19 January 2002
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 124 (6) , 978-983
- https://doi.org/10.1021/ja011895y
Abstract
In situ prepared copper catalysts Tp(X)Cu (Tp(X) = homoscorpionate) catalyze the olefin cyclopropanation reaction using ethyl diazoacetate as the carbene source. Very high values of both activity and diastereoselectivity toward the cis isomer have been obtained for styrene, alpha-methylstyrene, 1-hexene, 1-octene, vinyl acetate, n-butyl vinyl ether, 2,5-dimethyl-2,4-hexadiene, and 3,3-dimethyl-1-butene. The effect of the temperature in the diastereoselectivity was almost negligible within the range -10 to +30 degrees C. Kinetic studies have allowed us to propose that the homoscorpionate ligand might act in a dihapto form during the catalytic process. This transformation seems to operate under kinetic control, where the formation of the cis isomer would govern the reaction rate.Keywords
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