P. Hesemann et Jje. Moreau, Novel silica-based hybrid materials incorporating binaphthyl units: a chiral matrix effect in heterogeneous asymmetric catalysis, TETRAHEDR-A, 11(10), 2000, pp. 2183-2194
Polysilsesquioxane hybrid materials containing chiral binaphthyl moieties a
re 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 precurs
or, Rhodium species were embedded in the chiral hybrid matrix. The catalyti
c 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 Els
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