Reductive coupling of aromatic aldehydes promoted by an aqueous TiCl(3)ItBuOOH system in alcoholic cosolvents

The tert-butoxyl radical, generated by the aqueous Ti-III/ TBHP system, abstracts an H atom from alcoholic cosolvents (EtOH, iPrOH), leading to alpha-hydroxyalkyl radicals that reduce aromatic aldehydes to the corresponding 1,2-diols. The reactivities observed are explained by resonance stabilization of the a-hydroxybenzyl radicals formed in the electron-transfer (ET) process. Good Hammett-type correlations are obtained. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).