Chiral organometallic NADH mimics: Highly stereoselective reductions of ethyl benzoylformate with a 1,4-dihydronicotinoyl fragment attached to the homochiral auxiliary 5-C5H5)Fe(CO)(PPh3)> and possessing a homochiral β-hydroxy-carboxamide at C-5.

Article abstract of DOI:10.1016/S0957-4166(00)82187-4

A series of homochiral organometallic NADH mimics incorporating the chiral auxiliary <(η⁵-C5H5)Fe(CO)(PPh3)> at the C-3 carbonyl and a chiral carboxamide at C-5 of a 1,4-dihydronicotinoyl fragment have been prepared.These complexes were shown to stereoselectively reduce ethyl benzoylformate to either (R)- or (S)-ethyl mandelate by a combination of steric and chelation control.For example, complex (R,R)-12 bearing a carboxamide derived from (R)-(+)-methylbenzylamine afforded (R)-ethyl mandelate in 89percent enantiomeric excess.Utilisation of complexes (R,S)-19a and (R,R,S)-22a bearing chiral β-hydroxy-carboxamides derived from valinol and norephedrine respectively gave the (R)-ethyl mandelate in greater than 97percent enantiomeric excess.