Synthesis and characterization of chiral enantiopure PC(sp³)P pincer ligands and their complexes

This paper reports an efficient synthetic approach to preparing optically active PC(sp³)P pincer ligands and their complexes. The reported synthetic scheme relies on a simple and straightforward carbo-Diels–Alder reaction cycloaddition of a readily available phosphine precursor, 1,8-bis-(diphenylphosphino)anthracene (2) with enantiomerically pure bis-(methyl-(S)-lactyl) fumarate (3) leading to the formation of chromatographically resolvable diastereomers 4 and 4′ that can be converted into a pair of enantiomerically pure antipodes 1 and 1′. We demonstrated that no racemization occurs upon complexation and metalation of the bifunctional PC(sp³)P pincer ligands.