Copper(I)-homoscorpionate catalysts for the preferential, kinetically controlled cis cyclopropanation of alpha-olefins with ethyl diazoacetate.
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.
Díaz-Requejo
M Mar
MM
Departamento de Química y Ciencia de Materiales, Universidad de Huelva, Carretera de Palos de la Frontera s/n 21819-Huelva, Spain.
Caballero
Ana
A
Belderraín
Tomás R
TR
Nicasio
M Carmen
MC
Trofimenko
Swiatoslaw
S
Pérez
Pedro J
PJ