A promising new catalyst family for enantioselective cycloadditions involving allenes and imines: chiral phosphines with transition metal–CH2–P: linkages
作者:Alexander Scherer、J.A. Gladysz
DOI:10.1016/j.tetlet.2006.07.005
日期:2006.9
The racemic thenium-containing phosphine (eta(5)-C5H5)Re(NO)(PPh3)(CH2PPh3) (3) catalyzes the [3+2] cycloaddition of H2C=C=CHCO2Et and N-tosyl imines ArCH=NTs in C6H6 (RT, 1 d, 20 mol %) to give 2-aryl-3-carbethoxy-3-pyrrolines (Ar=p-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 degrees C (8 d) to maximize enantio selectivities (60-51% ee; 93-90% isolated). (c) 2006 Elsevier Ltd. All rights reserved.