A comparative study of diphosphine and phosphinamine palladium complexes on a new substrate for the intramolecular asymmetric Heck reaction

Palladium-catalysed intramolecular asymmetric Heck reactions were performed on triflate 5 using complexes derived from BINAP and a range of oxazoline-containing phosphinamine ligands. The optimum ee obtained was 85% employing the t-butyl-substituted ferrocenyloxazoline ligand 6. The isomer distribution of the product spirooxindoles was dependent on the ligand chosen, with the oxazoline-containing ligands showing an increased selectivity (up to 99:1) for the Δ2,3-isomer 3 compared to BINAP (optimum 75:25).