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.

Ruthenium-Catalyzed Transfer Hydrogenation for C–C Bond Formation: Hydrohydroxyalkylation and Hydroaminoalkylation via Reactant Redox Pairs

“…Conventional diol-alkyne transfer hydrogenation provides the initial quantities of dione required for entry into the catalytic cycle. 23,24,74 …”

Ru-catalyzed oxidation of primary alcohols

“…Ruthenium catalysts are known to oxidize alcohols and other substrates according to different reaction mechanisms such as hydridometal or oxometal pathways and even radical mechanism, depending on the oxidation states of ruthenium, oxidant and cocatalysts or additives [23][24][25][26][27][28][29][30][31][32][33][34][35]. Various homogeneous Ru catalysts, like RuCl 3 [36], perruthenate [37,38] or Ru complexes [20,39,40] preferentially with salen [41], amine [42][43][44]50] or phosphine [45][46][47][48][49][50][51] ligands, also in combination with bases and TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) as cocatalyst were successfully employed in the aerobic oxidation. Bäckvall and co-workers [52] developed methods for the oxidation of alcohols via biomimetic multi-stage electron transfers.…”

Ruthenium-Catalyzed Transfer Hydrogenation for C–C Bond Formation: Hydrohydroxyalkylation and Hydroaminoalkylation via Reactant Redox Pairs

“…Conventional diol-alkyne transfer hydrogenation provides the initial quantities of dione required for entry into the catalytic cycle. 23,24,74 Intermolecular catalytic reductive couplings of α-olefins with unactivated aldehydes and ketones remains an unmet challenge. [75][76][77] In a significant step toward this goal, it was found that ruthenium(0) catalysts promote the transfer hydrogenative C-C coupling of 3-hydroxy-2-oxindoles with α-olefins, including feedstocks such as ethylene, propylene and styrene, to furnish the branched adducts as single regio-and diastereomers.…”