Highly Enantioselective Pd(II)-Catalyzed Wacker-Type Cyclization of 2-Allylphenols by Use of Bisoxazoline Ligands with Axis-Unfixed Biphenyl Backbone.

Abstract A series of axis-unfixed bisoxazoline ligands with different steric and electronic properties has been synthesized. Due to the different steric interactions, the ligands afforded only one of the two possible diastereomeric Pd(II)-complexes upon metal coordination. The palladium complex ( S ,a S )- 8c showed excellent catalytic activities and enantioselectivities in Wacker-type cyclization of allylphenols with up to 98% ee.