Direct Conversion of Alcohols to Acetals and H2 Catalyzed by an Acridine-Based Ruthenium Pincer Complex

The crystallographically characterized ruthenium complex RuHCl(A-'Pr-PNP)(CO) (1) [A-'Pr-PNP = 4,5-bis-(diisopropylphosphinomethyl)acridine], which bears a nonplanar acridine moiety, catalyzes in a neutral medium the transformation of primary alcohols to the corresponding acetals with the liberation of H-2. In the presence of base, complex I catalyzes the dehydrogenative coupling of alcohols to form esters. Acetal formation may involve hemiacetal dehydration to form an enol ether followed by alcohol addition to the double bond.