Novel silica-based hybrid materials incorporating binaphthyl units: a chiral matrix effect in heterogeneous asymmetric catalysis

Polysilsesquioxane hybrid materials containing chiral binaphthyl moieties are readily available by coupling (R)- or (S)-2;2'-dihydroxy-1,1'-binaphthyl (BINOL) with 3-(triethoxysilyl)propyl isocyanate and subsequent hydrolysis polycondensation of the resulting bis-trialkoxysilylated carbamate precursor, Rhodium species were embedded in the chiral hybrid matrix. The catalytic properties of the solids were evaluated in hydride-transfer reduction to prochiral ketones, When the catalytic species were embedded in an entirely chiral network, enantiomeric excesses up to 45% were observed, (C) 2000 Elsevier Science Ltd. All rights reserved.