SHAPE-SELECTIVE OXIDATION OF BENZYLIC ALCOHOLS BY A RECEPTOR FUNCTIONALIZED WITH A DICOPPER(II) PYRAZOLE COMPLEX

A novel metallohost containing a substrate-binding site and two copper ions held by two bis-pyrazole ligand sets is described. The cavity of this molecule can bind dihydroxybenzene guests (association constants in chloroform are in the range K-a = 2000-3000 M(-1)). In the presenc e of benzylic alcohols the Cu(II) centers of the metallohost are reduc ed to Cu(I). During this process the alcohols are oxidized to aldehyde s. Benzylic alcohols possessing phenolic hydroxyl functions are extrem ely effective in the reduction reaction. It is believed that they are bound in the cavity of the metallohost and are oriented in the correct position with respect to the copper centers. This results in a rate e nhancement of at least 4 orders of magnitude for the oxidation reactio n.