cis-Semihydrogenation of alkynes with amine borane complexes catalyzed by gold nanoparticles under mild conditions

Abstract

Supported gold nanoparticles catalyze the semihydrogenation of alkynes to alkenes with ammonia borane or amine borane complexes in excellent yields and under mild conditions. Internal alkynes provide cis-alkenes, making this protocol an attractive alternative of the classical Lindlar's hydrogenation.

Reduction of the Diazo Functionality of α-Diazocarbonyl Compounds into a Methylene Group by NH3BH3 or NaBH4 Catalyzed by Au Nanoparticles

“…The monodeuterated 3b - d 1 was formed in 60% relative yield, along with dideuterated 3b - d 2 (15%) and non-deuterated 3b - d 0 (25%). The incorporation of H atoms from protic solvents in the Au/TiO 2 -catalyzed semireduction of alkynes using NH 3 BH 3 has been already shown by our group in the past [ 16 ]. An analogous H/D scrabbling pattern in products has been reported in the Pd-catalyzed hydrogenation of N -tosylhydrazones in MeOD [ 19 ].…”

“…At the outset, we investigated the possible Au/TiO 2 -catalyzed reduction of the model compound 1a into the desired product 3a, using the readily available boron hydride reagents NH 3 BH 3 and NaBH 4 . Ammonia borane complex [16,17] as well as sodium borohydride [18] have been used efficiently in the past for the reduction of alkynes or nitro compounds using Au/TiO 2 as catalyst. While no reaction occurs in a series of dry aprotic solvents (dichloromethane, diethyl ether, hexane, or benzene), to our pleasure, we found that the treatment of 1a with NH 3 BH 3 (0.4 molar equivalent) or NaBH 4 (0.3 molar equivalent) in MeOH for 15 min at room temperature resulted in the quantitative formation of the reduced product 3a (Scheme 2).…”

Stereoselective Transfer Semi‐Hydrogenation of Alkynes to E‐Olefins with N‐Heterocyclic Silylene–Manganese Catalysts

“…In addition to hydrogen storage, AB was successfully employed for transfer hydrogenation of various unsaturated organic substrates . This includes transfer semi‐hydrogenations of alkynes with Ni, Co, Au, and Cu complexes as precatalysts; Mn complexes, however, have merely been employed as precatalysts for H 2 evolution from AB, but not yet in transfer hydrogenation.…”

Efficient Synthesis of Functionalized β‐Keto Esters and β‐Diketones through Regioselective Hydration of Alkynyl Esters and Alkynyl Ketones by Use of a Cationic NHC–AuI Catalyst

“…Melting points were determined by using a visual melting range apparatus. Synthesis and data of many alkynyl ketones and alkynyl esters employed in this work are already reported in the literature …”