Article ID: 20140292
Asymmetric hydrogenation of α-phenylcinnamic acid catalyzed by cinchonidine (CD)-modified palladium has been performed. Without benzylamine (BA), a modification inconsistency was observed: the rate diminished when a small amount of CD was used, whereas the product enantiomeric excess (ee) increased when substantially more CD was used. By altering amount of amine additive, we deduced that this inconsistency was caused by the amine effect of CD itself. With a 1,8-diazabicyclo[5.4.0]undec-7-ene additive, the catalytic amount was sufficient to result in the highest ee of 81%.
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