From 2H-phospholes to BIPNOR, a new efficient biphosphine for asymmetric catalysis

For many years now, we have studied the 1H-/2H-phosphole equilibrium and its synthetic applications. On reaction with alkynes, 2H-phospholes yield the corresponding 1-phosphanorbornadienes. As ligands of rhodium(I), these phosphines show some potential in catalytic hydrogenation and hydroformylation of alkenes. Starting from 3,3',4,4'-tetramethyl-1,1'-biphospholyl and tolan, we have similarly obtained the corresponding 2,2'-bis-(1-phosphanorbornadienyl) (BIPNOR) with two chiral, non-racemisable, phosphorus atoms at the bridgeheads. The pure enantiomers of BIPNOR appear to be efficient ligands in asymmetric hydrogenation of C=C and C=O double bonds. (C) 1998 Elsevier Science S.A. All rights reserved.