Asymmetric 1,3-dipolar cycloaddition with a P-stereogenic dipolarophile: an efficient approach to novel P-stereogenic 1,2-diphosphine systems.

The asymmetric 1,3-dipolar cycloaddition of the P-stereogenic dipolarophile (S(p),S(p))-6 to C,N-diphenylnitrone (7) led to previously unknown P-stereogenic isoxazolinyl diphosphine dioxides (R(p),S(p))-8 in enantio- and diastereomerically pure form; their stereospecific reduction with Ti(OiPr)(4)/PMHS proceeds in high yield with retention of configuration at the phosphorus atoms to give enantio- and diastereomerically pure diphosphines, which are conveniently purified via the corresponding diphosphine-diboranes.