A promising new catalyst family for enantioselective cycloadditions involving allenes and imines: chiral phosphines with transition metal–CH2–P: linkages

The racemic rhenium-containing phosphine (η5-C5H5)Re(NO)(PPh3)(CH2PPh3) (3) catalyzes the [3+2] cycloaddition of H2CCCHCO2Et and N-tosyl imines ArCHNTs in C6H6 (RT, 1 d, 20 mol %) to give 2-aryl-3-carbethoxy-3-pyrrolines (Arp-C6H4X (X = H, NO2, OMe, Me, Cl, Br), 2-furyl; 95–84% isolated). Similar reactions with enantiopure (S)-3 are conducted in C6H5Cl at −30 °C (8 d) to maximize enantioselectivities (60–51% ee; 93–90% isolated).