Synthesis of enantiopure C1 symmetric diphosphines and phosphino-phosphonites with ortho-phenylene backbones

Abstract

Reaction of 2-(diphenylphosphino)phenylphosphonous acid tetramethyldiamide 1 with (+)-menthol, (1 S,2 S,3 S,5 R)-isopinocampheol and (1 R,2 R)- trans-cyclohexanediol affords enantiopure phosphino-phosphonite ligands 3– 5. The X-ray structures of 1 (space group P2 1/ n) and 3 (space group P2 1) have been determined. The reaction of 1 with (1 R,2 R,3 S,5 R)-(−)-pinanediol proceeds diastereoselectively to afford a novel type of enantiopure phosphino-phosphonite ligand 6 with an asymmetric substituted P atom. On reaction of (+)-cedryl alcohol with 1 the adduct 7 of the phosphonous acid 2-Ph 2PC 6H 4P(O)(H)OH 9 and its dimethylammonium salt is formed through elimination of water and subsequent hydrolysis. The structure of 7 (space group P1̄) was elucidated by X-ray structural analysis. Reduction of the chlorophosphine 8 with LiAlH 4 yields the novel primary–tertiary phosphine 10, which is a valuable starting material for the synthesis of the enantiopure C 1 symmetric bidentate phospholane ligands 11 and 12.