Shou‐Fei Zhu, Yu Fu, Jian-Hua Xie
Oct 17, 2003
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Influential Citations
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Journal
Tetrahedron-asymmetry
Abstract
Abstract Three chiral 4,4′-substituted 1,1′-spirobiindane-7,7′-diols and related monodentate spiro phosphoramidite ligands have been readily synthesized from enantiomerically pure 1,1′-spirobiindane-7,7′-diol. Excellent enantioselectivities were obtained with these new ligands in the rhodium-catalyzed asymmetric hydrogenation of dehydroamino acid derivatives and enamides. Comparing SIPHOS, ligands 4,4′-dibromo-SIPHOS and 4,4′-diphenyl-SIPHOS gave similarly high enantioselectivities although the rates in hydrogenations of enamides are somewhat slower. Methoxy substituents at the 4,4′-position of ligands slightly reduced enantioselectivities of hydrogenation reactions.