A. Palmer, A. Zanotti-gerosa, H. G. Nedden
Jun 16, 2008
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Influential Citations
10
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Journal
Tetrahedron-asymmetry
Abstract
Abstract The novel complex RuCl 2 [( S )-Xyl-P-Phos][( S )-DAIPEN] was identified as a highly active catalyst for the asymmetric reduction of a variety of prochiral ketones possessing an imidazo[1,2- a ]pyridine scaffold. The corresponding alcohols were obtained in excellent enantiomeric purities (>96% ee) and served as valuable intermediates for the synthesis of pharmacologically active 7 H -8,9-dihydropyrano[2,3- c ]imidazo[1,2- a ]pyridines. The complexity of these multi-functional substrates required the development of specific reaction conditions. Whereas the reduction with RuCl 2 [PP][NN] catalysts (Noyori catalysts) has never been reported to occur under aqueous conditions, in the present case, the use of aqueous isopropanol or tert -butanol was not only tolerated, but also turned out to be beneficial, especially when the reduction was conducted at high substrate to catalyst (S/C) ratios.