An aqueous acidic 15% solution of titanium trichloride is a fairly rapid, mild reducing agent (Eo=-0.1 V). This reagent has no effect on aliphatic or aromatic ketones and aldehydes. It easily couples carbonyl compounds activated toward reduction by an electron-withdrawing group, such as a pyridyl residue,'to the corresponding symmetrical diols. These diols are formed through dimerization of the intermediate stabilized capto-dative2 radicals. By ...
