Enantioselective syntheses of nonracemic benzyl-alpha-d alcohols via catalytic transfer-hydrogenation with Ru, Os, Rh, and Ir catalysts

摘要

The synthesis of chiral benzyl-a-d alcohols via the reduction of benialdehyde-a-d derivatives has been investigated with a. series of catalysts that were derived in situ from (1R,2S)- (+)-cis-1-amino-2-indanol and the chloro-bridged dimers of p-cymeneRu, p-cymeneOs, Cp*Rh, or Cp*Ir. An unusual trend was observed in which substrates containing electron-withdrawing substituents led to greater enantioenrichment than those with electron-donating substituents., All four catalyst systems were found to produce benzyl-a-d alcohols with high conversion (>98%). Modest to good enantioselectivites (up to 68% ee) were observed. [References: 24]