Tuning diastereoselectivity with the solvent: the asymmetric hydrogenation of simple and functionalized 1,3-diketones with ruthenium(amidophosphine–phosphinite) catalysts
MAHLER, ULRIKE;DEVANT, RALF M.;BRAUN, MANFRED, CHEM. BER., 121,(1988) N 11, C. 2035-2044
作者:MAHLER, ULRIKE、DEVANT, RALF M.、BRAUN, MANFRED
DOI:——
日期:——
Tuning diastereoselectivity with the solvent: the asymmetric hydrogenation of simple and functionalized 1,3-diketones with ruthenium(amidophosphine–phosphinite) catalysts
Spectacular
solvent effects in the asymmetric hydrogenation of methyl 3,5-dioxohexanoate (3) and 2,4-pentanedione
(5) have been observed using Ru[(S)-Ph,Ph-oxoProNOP]X2
complexes (X=η3-C4H7, IIa; CF3CO2, IIb; (R)-MTPA, IIc) as catalyst
precursors. β-Diketones 3 and 5 are respectively reduced to the corresponding β-diols 4 and 6. In both cases, an almost
complete reversal in the diastereoselectivity of the reaction is observed when changing the solvent from CH2Cl2
(syn-4 in up to 92% de; meso-6 in up to 84% de) to a 1:1 CH2Cl2âCH3OH mixture (anti-4
and anti-6 in up to 84% de).
The extent of this
solvent effect
is much less
marked with Ru-atropisomeric
diphosphine catalysts.