Triruthenium dodecacarbonyl/triphenylphosphine catalyzed dehydrogenation of primary and secondary alcohols

Abstract Dehydrogenation of alcohols into aldehydes and ketones by Ru 3 (CO) 12 /PPh 3 based homogeneous catalysis has been investigated as an alternative for the classical Oppenauer oxidation. Several catalytic systems have been screened in the Oppenauer-like oxidation of alcohols. A systematic study of various combinations of Ru 3 (CO) 12 , mono- and bidentate ligands and hydride acceptors was performed to enable dehydrogenation of primary alcohols to stop at the aldehyde stage. Among many H-acceptors screened, diphenylacetylene (tolane) proved the most suitable judged from its smooth reduction. Electron rich and deficient analogues of tolane have been synthesized and, based on competition experiments between these H-acceptors, a tentative catalytic cycle for the Ru 3 (CO) 12 /PPh 3 -catalyzed dehydrogenations has been proposed.