Double Dehydrogenation of Primary Amines to Nitriles by a Ruthenium Complex Featuring Pyrazole Functionality

Abstract

A ruthenium(II) complex bearing a naphthyridine-functionalized pyrazole ligand catalyzes oxidant-free and acceptorless selective double dehydrogenation of primary amines to nitriles at moderate temperature. The role of the proton-responsive entity on the ligand scaffold is demonstrated by control experiments, including the use of a N-methylated pyrazole analogue. DFT calculations reveal intricate hydride and proton transfers to achieve the overall elimination of 2 equiv of H.

Aerobic dehydrogenation of amines to nitriles catalyzed by triazolylidene ruthenium complexes with O2 as terminal oxidant

“…After these initial stages, complex 5 and 7 show similar catalytic profile with formation of nitrile in 81% and 79% yield respectively, suggesting the evolution of an identical catalytic species, which supports the initial loss of cymene from complex 5. However, the solvento complex 7 showed only very modest activity at lower temperature and reached a mere 50% conversion after 3 d at 80°C, indicating that unlike N-coordinated systems, 29,51 high temperatures are needed also for the catalytic dehydrogenation and not only for cymene dissociation during catalyst activation. We note that nitrile formation was more favored when running the catalysis with complex 7 under higher concentration of ammonia gas (30 instead of 6 mL), reaching 71% nitrile and 22% imine after 10 min, and almost full conversion to nitrile (95% yield) after 20 min reaction (Fig.…”

“…21 Later on Parvulescu introduced a faster novel ruthenium-terpyridyl complex that showed conversion of amines to nitriles after 2 h when using 5 atm of oxygen at 60°C, 25 while Maiti and co-workers developed new ruthenium hydrido complexes for the selective generation of nitriles and imines by varying the catalyst instead of the substrates. 26 More recently, different N-chelated ruthenium complexes [27][28][29] as well as simple [Ru(arene)Cl 2 ] 2 complexes have been demonstrated to be highly competent in amine dehydrogenation. 30,31 Herein we describe new ruthenium(II) complexes featuring a range of functionalized triazolylidene ligands and their catalytic activity in amine oxidation.…”

Selective Acceptorless Dehydrogenation of Primary Amines to Imines by Core–Shell Cobalt Nanoparticles

“…From the reaction profile as shown in Figure , in which nitrile formation is not observed, it would appear that the transamination step is much faster than the second dehydrogenation of the aldimine intermediate, which differs to the reactivity observed for homogeneous catalysts . After 12 h, the imine was obtained in 96 % yield.…”

Vacancy‐Rich Ni(OH)2 Drives the Electrooxidation of Amino C−N Bonds to Nitrile C≡N Bonds

“…Broadly accepted, the first step of dehydrogenation is considered the rate-determining step in the dehydrogenation activation reaction of C À Nbonds. [28] As such, the subsequent chemical activation process was also explored by simulating the first step of dehydrogenation in detail. Thefirst dehydrogenation of propylamine to propionitrile was discussed in two cases:dehydrogenation of N(define as route 1) and adjacent carbon atoms (define as route 2).…”