Highly enantioselective Pd(II)-catalyzed Wacker-type cyclization of 2-allylphenols by use of bisoxazoline ligands with axis-unfixed biphenyl backbone

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,aS)-8c showed excellent catalytic activities and enantioselectivities in Wacker-type cyclization of allylphenols with up to 98% ee.