Functional modeling of alcoholdehydrogenase with pyrazolylborate-zinc complexes

Unlike free isopropanol, the complex Tp(Cum,Me)Zn-OCHMe2 (Tp(Cum,Me) = tris (3-cumenyl-5-methylpyrazolyl)borate) is oxidized by N-benzylnicotinamide ch loride to acetone and Tp(Cum,Me)Zn-Cl in small yield. The stronger oxidant 2,3-dichloro-5,6-dicyanobenzoquinone oxidizes Tp(Cum,Me)Zn-phenolates with o-hydroxymethyl substituents to the corresponding zinc phenolates with o-fo rmyl substituents. Benzaldehydes with electronegative substituents (F, NO2, CF3) are reduced by N-benzyldihydronicotinamide in the presence of Tp(Cum, Me)Zn-OH to the corresponding benzyl alcohols which are isolated as Tp(Cum, Me)Zn-OCH2Ar. A kinetic analysis has shown that the reduction of the aldehy des alone is roughly two times slower than that in the presence of the zinc complex. (C) 2001 Elsevier Science B.V. All rights reserved.