Synthesis of 1,5-P,N-phosphino-sulfoximines through phospha-Michael reaction of alkenyl sulfoximines and their evaluation as ligands in palladium-catalyzed allylic alkylation

We describe a modular synthesis of cyclic and acyclic 1,5-P,N-phosphino-sulfoximines by using a phospha-Michael reaction of the corresponding alkenyl sulfoximines with HPPh2/KOtBu as key step, which proceeds with medium diastereoselectivity. The palladium-catalyzed allylic alkylation of racemic 1,3-diphenyl allyl acetate with malonate in the presence of a SSRCRC-configured N-benzyl-substituted cyclic phosphino-sulfoximine gave the corresponding alkene with 97% ee in 98% yield. A comparative study of N-substituted phosphino-sulfoximines showed the selectivity of the Pd(0)-catalyst to be dependent not only on the chiral backbone of the ligand but also on the N-substituent and configuration of the sulfoximine group.