Ruthenium‐Catalyzed Regioselective Deuteration of Alcohols at the β‐Carbon Position with Deuterium Oxide

A convenient method for regioselective H/D exchange between D(2)O and alcohols at the β-carbon position using the catalytic system [(p-cymene)RuCl(2)]/ethanolamine/KOH is described. This method is applicable for deuteration of both primary and secondary alcohols. The H/D exchange reactions proceed through an oxidation/modification/reduction reaction sequence. Alcohols are first temporarily oxidized to carbonyl compounds by the hydrogen transfer catalyst. The carbonyl compounds then undergo deuteration at the carbon adjacent to the carbonyl group by keto-enol tautomerization in the presence of D(2)O and a catalytic amount of base. The deuterated carbonyl compounds are then reduced to produce deuterated alcohols. In support of the reaction mechanism, a well-defined bimetallic ruthenium complex was isolated from the reaction of [{(p-cymene)RuCl(2)}(2)] with ethanolamine. The activity of this complex is similar to that of [{(p-cymene)RuCl(2)}(2)]/ethanolamine.