3525-72-2Relevant academic research and scientific papers
In Situ Generated Cobalt Catalyst for the Dehydrogenative Coupling of Alcohols and Amines into Imines
Bottaro, Fabrizio,Madsen, Robert
, p. 2707 - 2712 (2019/05/15)
An in situ formed cobalt catalyst is developed from cobalt(II)bromide, bis[2-(diisopropylphosphino)-4-methylphenyl]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.
Development and mechanistic investigation of the manganese(iii) salen-catalyzed dehydrogenation of alcohols
Samuelsen, Simone V.,Santilli, Carola,Ahlquist, M?rten S. G.,Madsen, Robert
, p. 1150 - 1157 (2019/02/03)
The first example of a manganese(iii) catalyst for the acceptorless dehydrogenation of alcohols is presented. N,N′-Bis(salicylidene)-1,2-cyclohexanediaminomanganese(iii) chloride (2) has been shown to catalyze the direct synthesis of imines from a variety of alcohols and amines with the liberation of hydrogen gas. The mechanism has been investigated experimentally with labelled substrates and theoretically with DFT calculations. The results indicate a metal-ligand bifunctional pathway in which both imine groups in the salen ligand are first reduced to form a manganese(iii) amido complex as the catalytically active species. Dehydrogenation of the alcohol then takes place by a stepwise outer-sphere hydrogen transfer generating a manganese(iii) salan hydride from which hydrogen gas is released.
Cobalt-Catalyzed Dehydrogenative Coupling of Amines into Imines
Bottaro, Fabrizio,Takallou, Ahmad,Chehaiber, Ahmad,Madsen, Robert
supporting information, p. 7164 - 7168 (2019/11/16)
Primary amines have been subjected to an acceptorless dehydrogenative homo- and heterocoupling into imines with a cobalt catalyst. The catalytically active species are composed of cobalt nanoparticles, which are generated in situ by heating Co2(CO)8 in the presence of trioctylphosphine oxide as a surfactant. The nanoparticles have been characterized by transmission electron microscopy where the image showed spherical and small particles with a narrow size distribution. The catalyst can be recovered and used again with essentially no effect on the yield. The catalyst can also be used for the dehydrogenative coupling of alcohols and amines into imines.
H2 Activation by Non-Transition-Metal Systems: Hydrogenation of Aldimines and Ketimines with LiN(SiMe3)2
Elliott, Daniel C.,Marti, Alex,Mauleón, Pablo,Pfaltz, Andreas
supporting information, p. 1918 - 1922 (2019/01/16)
In recent years, H2 activation at non-transition-metal centers has met with increasing attention. Here, a system in which H2 is activated and transferred to aldimines and ketimines using substoichiometric amounts of lithium bis(trimethylsilyl)amide is reported. Notably, the reaction tolerates the presence of acidic protons in the α-position. Mechanistic investigations indicated that the reaction proceeds via a lithium hydride intermediate as the actual reductant.
Molybdenum-Catalyzed Dehydrogenative Synthesis of Imines from Alcohols and Amines
Azizi, Kobra,Madsen, Robert
, p. 3703 - 3708 (2018/07/31)
A molybdenum N-heterocyclic carbene catalyst has been developed for the synthesis of imines from primary alcohols and amines with the liberation of dihydrogen. The catalyst is generated in situ from molybdenum hexacarbonyl, 1,3-dicyclohexylimidazolium chloride and potassium tert-butoxide and is further stabilized by the phosphine ligand dppe. Imines are formed in moderate to good isolated yields and a variety of alcohols and amines can be employed in the reaction including anilines. The transformation constitutes the first example of a homogeneous molybdenum-catalyzed acceptorless dehydrogenative coupling with alcohols and is believed to proceed by formation of a cis-coordinated molybdenum bis-N-heterocyclic carbene complex, which performs an oxidative addition to the alcohol, β-hydride elimination and reductive elimination of dihydrogen.
Ortho Metalation Directed by α-Amino Alkoxides
Comins, Daniel L.,Brown, Jack D.
, p. 1078 - 1083 (2007/10/02)
The addition of aromatic aldehydes to certain lithium dialkylamides in benzene or tetrahydrofuran gave α-amino alkoxides which were ortho lithiated with excess n-butyllithium.Subsequent alkylation and hydrolysis provided ortho-substituted aromatic aldehydes via a one-pot reaction.The ortho metalation of α-amino alkoxides derived from 1- and 2-naphthaldehyde and various substituted benzaldehydes was examined.When N,N,N'-trimethylethylenediamine was used as the amine component of the α-amino alkoxide, metalation could be carried out at lower temperatures.This rate increase is due to an intramolecular TMEDA-like assisted metalation.The synthetic utility of this ortho metalation, including how varying the amine component of the α-amino alkoxide affects the regiochemistry and metalation rate, is discussed.
