In Situ Generated Cobalt Catalyst for the Dehydrogenative Coupling of Alcohols and Amines into Imines

Abstract

An in situ formed cobalt catalyst is developed from cobalt(II)bromide, bis[2-(diisopropylphosphino)-4methylphenyl]amine and zinc metal. The catalyst mediates the acceptorless dehydrogenative coupling of alcohols and amines into imines with the release of hydrogen gas and the transformation is applied to the synthesis of a variety of imines from different alcohols and amines. The mechanism is investigated with labelled substrates and based on the results a cobalt(I) PNP complex is believed to be the catalytically active species which abstracts hydrogen gas from the alcohol through a metal ligand bifunctional pathway. Convenient cobalt:A cobalt catalyst is formed in situ from CoBr2, a PNP ligand and Zn and shown to mediate the synthesis of imines from alcohols and amines with the release of hydrogen gas. The catalytically active species is believed to be a cobalt(I) complex, which removes hydrogen gas from the alcohol by a metal ligand bifunctional mechanism.

Nickel Complexes Bearing N,N,O-Tridentate Salicylaldiminato Ligand: Efficient Catalysts for Imines Formation via Dehydrogenative Coupling of Primary Alcohols with Amines

“…The acceptorless dehydrogenative coupling (ADC) of alcohols and amines is one of the promising strategies for the construction of C–N bond, in which H 2 and H 2 O are the only byproducts and without preactivating the hydroxide to a better leaving group . This process can be accomplished in one pot without using any oxidant or hydrogen acceptor and can be applied to the synthesis of various valuable nitrogen-containing compounds like amines, imines, amides, N -heterocycles, , etc. The ADC reactions are usually catalyzed by precious metals, where especially iridium and ruthenium-based catalysts have been predominantly investigated. ,, In the past few years, a trend has drifted toward the usage of earth-abundant and inexpensive metals such as iron, cobalt, and manganese .…”

Diastereoselective diazenyl formation: the key for manganese-catalysed alcohol conversion into (E)-alkenes

“…16 Definitively, these are just a few instances amongst the plethora of organic transformations catalysed by manganese that have been reported in the last lustrum. [17][18][19][20][21][22][23][24][25][26] Encouraged by our interests in the unravelling of the mechanistic aspects in the catalytic chemistry of manganese, [27][28][29][30] the recent work by Milstein et al, 31 reporting for first-time a manganese-catalysed coupling of alcohols and hydrazone to form alkenes, caught our attention. As an alternative to the classical approaches for the synthesis of olefins from carbonyl compounds (such as Wittig, 32 Peterson, 33 or Julia 34 olefinations), Milstein and co-workers offer an unprecedented base-and waste-free procedure for the direct transformation of alcohols into alkenes.…”

Ionic‐Liquid‐Catalyzed Synthesis of Imines, Benzimidazoles, Benzothiazoles, Quinoxalines and Quinolines through C−N, C−S, and C−C Bond Formation

“…N ‐Cyclohexyl‐1‐(4‐chlorophenyl)methanimine (4 b) [20] Yield (164 mg, 65 % yield, colorless oil). eluent: 5 % ethyl acetate/hexane; 1 H NMR (500 MHz, Chloroform‐ d ) δ 8.15 (s, 1H), 7.55 (d, J =8.4 Hz, 2H), 7.25 (d, J =8.6 Hz, 2H), 3.09 (td, J =10.6, 5.3 Hz, 1H), 1.73 (dt, J =12.4, 3.1 Hz, 2H), 1.65–1.55 (m, 3H), 1.48 (qd, J =12.7, 3.4 Hz, 2H), 1.30–1.13 (m, 3H).…”