Optical resolution of tetra isopropyl-substituted spiro bis(isoxazoline)i-Pr-SPRIX

The optical resolution of racemic tetra isopropyl-substituted spiro bis(isoxazoline) ligand (i-Pr-SPRIX) is achieved by fractional recrystallization of palladium complexes 2a and 2b prepared from (±)-SPRIX 1 and di-μ-chlorobis{(R)-2-[1-(dimethylamino)ethyl]phenyl-C,N}dipalladium(II) (R,R)-3 followed by the decomplexation from palladium by the treatment with 1,2-bis(diphenylphosphino)ethane. The X-ray crystal structure of the complex 2a reveals that (−)-i-Pr-SPRIX has (P,R,R)-configuration.