Amidophosphine-phosphinites: Synthesis and use in rhodium-based asymmetric hydrogenation of activated keto compounds. Crystal structure of bis[(μ-chloro)((S)-2-((diphenylphosphino)oxy)-2-phenyl-N-(diphenylphosphino)- N-methylacetamide)rhodium(I)]

Alain Roucoux, Laurent Thieffry, J. F. Carpentier, Marc Devocelle, Catherine Méliet, Francine Agbossou, André Mortreux, Alan J. Welch

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Abstract

Amidophosphine-phosphinite ligands (AMPP) derived from (S)-N-benzylmandelamide ((S)-R,R'-benzylmandelNOP (S)-1 (R = R' = phenyl) and (S)-7 (R = phenyl, R' = cyclopentyl)), (S)-N-methylmandelamide ((S)-R,R'-methylmandelNOP (S)-2 (R = R' = phenyl) and (S)-8 R = phenyl, R' = cyclopentyl)), (S)-N-methyllactamide ((S)-R,R'-methyllactaNOP (S)-3 (R = R' = phenyl) and (S)-9 (R = phenyl, R' = cyclopentyl)), and (S)-2-hydroxymethyl)-2-pyrrolidinone ((S)-R,R'-oxoProNOP (S)-4-6 and (S)-10 (R, R' = phenyl, cyclohexyl, cyclopentyl)) have been prepared in high yields (60-94%) and reacted with rhodium Precursors to prepare neutral "Rh{AMPP}" complexes 11-26 of general formula [Rh{AMPP}X]2, where X = Cl, I, OCOCH3, OCOCF3, and OCOC3F7. The crystal structure of [Rh{(S)-Ph,Ph-methylmandelNOP}Cl]2 (12) has been determined. The rhodium atom has a cis square-planar coordination, and the seven-membered chelate ring has a boat conformation with the nitrogen atom in the mean plane RhP2. Complexes 11-26 have been used as catalyst precursors for the asymmetric hydrogenation of dihydro-4,4-dimethyl-2,3-furandione (27) and N-benzylbenzoylformamide (29) giving the corresponding optically active hydroxy compounds 28 and 30 in high yields and low to high enantiomeric excesses (28-98.7% ee and 13-87% ee, respectively). Catalytic activities (turnover frequency at 50% conversion at room temperature up to 3300 h-1) as well as the enantioselectivities depended strongly on the nature of the substituents on phosphorus as well as on the nature of the non chiral ligands. Catalyst precursor [Rh{(S)-Cp,Cp-oxoProNOP}OCOCF3]2 afforded (R)-pantolactone in 98.7% ee.

Original languageEnglish
Pages (from-to)2440-2449
Number of pages10
JournalOrganometallics
Volume15
Issue number10
Publication statusPublished - 14 May 1996

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