A new route to chiral bis-tertiary phosphine ligands: synthesis, resolution, and crystal structure of trans-bis-1,2-(diphenylphosphino)-cyclopentane and the nickel adduct NiBr2[trans-1,2-(PPh2)2C5H8]

Abstract

Heating of white phosphorus, phosphorus trichloride, and cyclopentene at 220 "C gives trans-I ,2bis(dich1orophosphino)cyclopentane ( I ) , which with phenylmagnesium bromide gives trans-l,2-bis(diphenylphosphino)cyclopentane (dpcp) (2); compound (2) forms the adduct Ni(dpcp) Br2.CH2C12, which readily crystallises as a conglomerate and the pure eqantiomers may be separated by hand allowing resolution of (2), and catalytic hydrogenation of methyl(N-benzoy1)dehydrophenylalanine using resolved (2) and a rhodium catalyst gave a hydrogenated product of 100% optical purity.-179 + 4".

Bisphosphine ligands containing two o-N,N-dimethylanilinyl substituents at each phosphorus atom

“…It is constructive to consider structural features of dmapm, dmape, and dmapcp along with those of their phenyl analogues: bis(diphenylphosphino)methane, dppm (32), 1,2-bis(diphenylphosphino)ethane, dppe (33), and dppcp (see above) (22), and those we have determined for the pyridyl analogues dpype (20) and dpypcp (20,34), respectively. As far as we are aware, the pyridyl analogue of dmapm has not been reported.…”

“…The precursor 1,2-bis(dichlorophosphino)cyclopentane was made by reaction of cyclopentene, white phosphorus, and PCl 3 (22). This procedure results almost exclusively in the trans product and, because of this, dmapcp is produced as a racemic mixture of R,R-and S,S-enantiomers, as with the 1,2-bis(diphenylphosphino)cyclopentane analogue, dppcp (22); the chirality designators refer to the absolute configurations of the methine C atoms 1 and 2 in the backbone of the ligand (Figs.…”

“…The precursors 1,1-bis(dichlorophosphino)methane and 1,2-bis(dichlorophosphino)ethane were purchased from commercial sources and stored in an N 2 -filled glovebox, while 1,2-bis(dichlorophosphino)cyclopentane was made according to a literature procedure (22) and stored in a Schlenk tube under Ar. N,N-Dimethyl-o-bromoaniline was made by reaction of o-bromoaniline and dimethylsulfate according to a literature procedure (23); all other reagents were purchased from commercial sources and used as supplied.…”

Enantioselective Catalysis; 130: Optically Active Expanded Ligands Based on the trans-1,2-Substituted Cyclopentane Skeleton

“…Promoted by a phase transfer catalyst, under the two-phase conditions, the ligands (R,R)-21a and (S,S)-21b maintained their high enantioselectivities known from monophasic hydrogenations, whilst the conventional phosphanes suffered a great loss of their selectivity. For (R,R)-21a and (S,S)-21b 60-80% ee were achieved in several experiments, but only 23% ee for dpcp, 8 and less than 5% ee for diop 20 and norphos. 21 Only small amounts of water were used in the system (aqueous slurry of substrate) in order to assure complete hydrogenation.…”

Asymmetric synthesis of phosphines via chiral cyclopalladium(II) complexes promoted reactions

“…Several excellent chiral C^-symmetric chelating bisphosphines were also discovered. These include BDPP 37 , NorPhos 38 , DPCP 39 , CBD 4 , PyrPhos 41 and 6 42 . Most of them are 1,2-bisphosphines.…”