1,3-Ferrocenyldiols are useful starting material to gain access to a new class of ferrocene ligands bearing two coordinating groups on the side chain, since the acetoxygroup in the alpha position with respect the cyclopentadienyl ring can be selectively substituted with amines or other nucleophiles. The enantioselective reduction of a carbonyl group is a powerful tool to prepare optically active secondary alcohols and among the different available methodologies we investigated the transfer hydrogenation promoted by a Ru-complex. A serie of 1,3-ferrocenyldiketones was subjected to asymmetric reduction in the presence of HCOOH/TEA mixture as hydrogen donor and (R,R)-RuCl[N-(tosyl)-1,2-diphenylethylendiamine](p-cymene). In all the cases the reduction of the carbonyl group far away the ferrocene moiety was observed and ferrocenylaldols with up to 99% ee were obtained, depending on the substrate structure. The ferrocenylaldols were then converted into the corresponding diols, whose stereochemistry was determined by detailed NMR analyses, and the synthetic route to new ferrocenylaminoalcohols is also described .
Asymmetric reduction of 1,3-ferrocenyldiketones
Patti A;Pedotti S
2006
Abstract
1,3-Ferrocenyldiols are useful starting material to gain access to a new class of ferrocene ligands bearing two coordinating groups on the side chain, since the acetoxygroup in the alpha position with respect the cyclopentadienyl ring can be selectively substituted with amines or other nucleophiles. The enantioselective reduction of a carbonyl group is a powerful tool to prepare optically active secondary alcohols and among the different available methodologies we investigated the transfer hydrogenation promoted by a Ru-complex. A serie of 1,3-ferrocenyldiketones was subjected to asymmetric reduction in the presence of HCOOH/TEA mixture as hydrogen donor and (R,R)-RuCl[N-(tosyl)-1,2-diphenylethylendiamine](p-cymene). In all the cases the reduction of the carbonyl group far away the ferrocene moiety was observed and ferrocenylaldols with up to 99% ee were obtained, depending on the substrate structure. The ferrocenylaldols were then converted into the corresponding diols, whose stereochemistry was determined by detailed NMR analyses, and the synthetic route to new ferrocenylaminoalcohols is also described .I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
