(1R,1′R,2S,2′S)-2,2′-Bis(1,1-dimethylethyl)-2,2′,3,3′-tetrahydro-1,1′-bi-1H-isophosphindole and (1S,1′S,2R,2′R)-2,2′-Bis(1,1-dimethylethyl)-2,2′,3,3′-tetrahydro-1,1′-bi-1H-isophosphindole

Abstract

[528814-26-8] C24H32P2 (MW 382.46) InChI = 1S/C24H32P2/c1-23(2,3)25-15-17-11-7-9-13-19(17)21(25)22-20-14-10-8-12-18(20)16-26(22)24(4,5)6/h7-14,21-22H,15-16H2,1-6H3/t21-,22-,25+,26+/m1/s1 InChIKey = HCBRTCFUVLYSKU-PWGHIRGTSA-N [795290-34-5] C24H32P2 (MW 382.46) InChI = 1S/C24H32P2/c1-23(2,3)25-15-17-11-7-9-13-19(17)21(25)22-20-14-10-8-12-18(20)16-26(22)24(4,5)6/h7-14,21-22H,15-16H2,1-6H3/t21-,22-,25+,26+/m0/s1 InChIKey = HCBRTCFUVLYSKU-CNXCYTMISA-N (optically active reagent used as a ligand for asymmetric catalysis; its rhodium(I) complexes are highly enantioselective catalysts in homogeneous asymmetric hydrogenation reactions) Alternate Names: (1R,1′R,2S,2′S)-DuanPhos and (1S,1′S,2R,2′R)-DuanPhos. Physical Data: mp 214–246 °C, +18° (c = 1.0, CH3Cl) for the (1R,1′R,2S,2′S)-enantiomer. Solubility: soluble in THF, CH2Cl2, and other common organic solvents. Analysis of Reagent Purity: optical rotation; NMR spectroscopy. Form Supplied in: colorless crystals, Sigma–Aldrich. Preparative Methods: the DuanPhos ligands are readily synthesized from 1,2-benzenedimethanol (eq 1).1 The derived cyclic sulfate is treated with tert-butylphosphine in the presence of n-BuLi, followed by oxidation with H2O2, to afford the corresponding phosphine oxide. Homocoupling of the phosphine oxide in the presence of CuCl2 and LDA gives the racemic bis(phosphine) oxide, followed by resolution with l-DBT·H2O. The (1R,1′R,2S,2′S)-enantiomer is obtained by reduction of the enantiomerically pure bis(phosphine) oxide with trichlorosilane in the presence of triethylamine. Similarly, the (1S,1′S,2R,2′R)-enantiomer is obtained by resolution with d-DBT·H2O. (1) Purification: passing through a short silica gel plug under N2 afforded the pure phosphine. Handling, Storage, and Precautions: although an ether solution of DuanPhos was exposed to air overnight without any oxidation detected,1 the reagent is still considered air-sensitive and should be handled and stored under an inert atmosphere. Toxicity data are not available.