Filling the Gaps in the Challenging AsymmetricHydroboration of 1,1-Disubstituted Alkenes with Simple Phosphite-Based Phosphinooxazoline Iridium Catalysts

Identifier:  PC:1257

Handle: https://hdl.handle.net/20.500.11797/PC1257

Authors:  Montserrat Diéguez; Maria Biosca; Marc Magre; Oscar Pàmies

Abstract:
We have identified a readily accessible phosphinooxazoline based phosphite-oxazoline catalytic system, (S)-4-isopropyl-2-{2-[(3,3¿,5,5¿-tetra-tert-butyl-1,1¿-biphenyl-2,2¿-diyl)phosphite]-phenyl}-2-oxazoline (L1 a), that can hydroborate a range of 1,1-disubstituted aryl olefins with high enantioselectivity (up to 94%), excellent yields and perfect regioselectivity. The new phosphite-oxazoline ligands efficiently hydroborate a broader range of olefins than previous phosphinooxazoline ligands. In particular, a wide range of a-tert-butylstyrenes can be hydroborated that bear aryl substituents with different electronic and steric properties, which complements previous results with N-heterocyclic copper catalysts, the only other system reported to date that has achieved these reactions.