Chiral transition metal complexes containing phosphines: Synthesis, characterization, and application in catalytic reactions.

摘要

Chiral rhodium(III) and ruthenium(II) complexes were designed to serve as stereoselective catalysts. These complexes contained the bidentate phosphine ligands, 2,2′-bis(diphenylphosphino)-1,1′ -binaphthyl (BINAP), monoxidized BINAP (BINPO), 1,1′ -bis(diphenylphosphino)methane monoxide (dppmO), (1-(diphenylphosphino)ethyl)diphenylphosphine oxide (Ph₂PCH(CH₃)P(O)Ph₂), 2-dicyclohexylphosphino-2 ′-(N,N-dimethylamino)biphenyl (Me₂NC ₆H₄C₆H₄PCy₂), 2-(dicyclohexylphosphino)biphenyl, and 2-(dicyclohexylphosphino)-2′-methylbiphenyl. The catalysts were applied in several stereoselective reactions.; In the hydrosilylation of phenylacetylene, [Cp*Rh((S)-BINAP)](SbF ₆)₂ was found to generate β-E vinylsilanes preferentially and gave especially high regioselectivity and stereoselectivity with triphenylsilane (>99%).; Each complex catalyzed the asymmetric Diels-Alder reaction of methacrolein with cyclopentadiene in the following ee: [Cp*Rh(( S)-BINAP)](SbF₆)₂, 51% (S-exo); [(p-cymene)Ru((S)-BINAP)](SbF₆) ₂, 50% (R-exo); [Cp*Rh((S)-BINPO)](SbF ₆)₂, 9% (R-exo); [Cp*Rh(η2-Ph ₂PCH(CH₃)P(O)Ph₂-P,O)](SbF ₆)₂, 21–38% (S-exo); [Ru(η 6:η1-Me₂NC₆H₄C ₆H₄PCy₂-P)(PPh₃)](SbF ₆)₂, ∼20%. Racemic [Cp*Rh(η2-Ph ₂PCH(CH₃)P(O)Ph₂-P,O)](SbF ₆)₂ catalyzed the reaction via chiral poisoning by (1R)-(+)-camphor and L-proline. Tethered, chiral-at-metal, [Ru(η6:η1-Me₂ NC₆H₄C₆H₄PCy₂- P)(PPh₃)Cl]SbF₆, which resolved spontaneously upon recrystallization, served as the enantiopure precursor of [Ru(η 6:η1-Me₂NC₆H₄C ₆H₄PCy₂-P)(PPh₃)](SbF ₆)₂.; The asymmetric transfer hydrogenation of 1′-acetonaphthone with 2-propanol was catalyzed by the racemic, tethered compound, [Ru(η 6:η1-Me₂NC₆H₄C ₆H₄PCy₂-P)Cl₂], generating (R)-1-(1-naphthyl)ethanol in 33% ee.; To evaluate the catalyst design, the effect of each transition metal catalyst's structure and chirality on product stereoselectivity was assessed.