53441-73-9Relevant academic research and scientific papers
Hydroboration Catalyzed by 1,2,4,3-Triazaphospholenes
Tien, Chieh-Hung,Adams, Matt R.,Ferguson, Michael J.,Johnson, Erin R.,Speed, Alexander W. H.
supporting information, p. 5565 - 5568 (2017/10/25)
The synthesis and study of the catalytic activity of 1,2,4,3-triazaphospholenes (TAPs) is reported. TAPs represent a more modular scaffold than previously reported diazaphospholenes. TAP halides were shown to catalyze the 1,2 hydroboration of 19 imines, and three α,β unsaturated aldehydes with pinacolborane, including examples that did not undergo hydroboration by previously reported diazaphospholene systems. DFT calculations support a mechanism where a triazaphospholene cation interacts with the substrate, a mechanism distinct from diazaphospholene catalyzed hydroborations.
Asymmetric Imine Hydroboration Catalyzed by Chiral Diazaphospholenes
Adams, Matt R.,Tien, Chieh-Hung,McDonald, Robert,Speed, Alexander W. H.
supporting information, p. 16660 - 16663 (2017/12/13)
The first use of diazaphospholenes as chiral catalysts has been demonstrated with enantioselective imine hydroboration. A chiral diazaphospholene prepared in a simple three-step synthesis from commercial materials has been shown to achieve the highest enantioselectivity for the hydroboration of alkyl imines with pinacolborane reported to date. Enantiomer ratios of up to 88:12 were obtained with low (2 mol %) catalyst loadings. Twenty examples of asymmetric reduction employing this main-group catalysis protocol, including the synthesis of the pharmaceuticals ent-rasagiline and fendiline, are shown.
Asymmetric hydrogenation of N-alkyl and N-aryl ketimines using chiral cationic Ru(diamine) complexes as catalysts: The counteranion and solvent effects, and substrate scope
Chen, Fei,Ding, Ziyuan,He, Yanmei,Qin, Jie,Wang, Tianli,Fan, Qing-Hua
supporting information; experimental part, p. 5248 - 5257 (2012/08/08)
Asymmetric hydrogenation of N-alkyl and N-aryl ketimines catalyzed by chiral cationic η6-arene-(N-monosulfonylated diamine) Ru(II) complexes has been investigated. Strong counteranion and solvent effects on the enantioselectivity were observed. The ruthenium catalyst bearing non-coordinating BArF- anion was found to be particularly effective for the hydrogenation of acyclic and exocyclic N-alkyl ketimines in the presence of (Boc)2O in dichloromethane or even under solvent-free conditions, providing chiral amines with up to >99% ee and full conversions. Alternatively, the ruthenium catalyst bearing achiral phosphate anion together with corresponding phosphoric acid as the additive was also efficient for the hydrogenation of N-alkyl ketimines in the absence of (Boc)2O with excellent enantioselectivities and full conversions. For N-aryl ketimines lower enantiomeric excesses were observed by using the ruthenium catalyst bearing BArF- anion. This catalytic protocol thus provides a facile and practical access to optically active amines and has been successfully employed in the gram-scale synthesis of enantiomerically pure (+)-sertraline.
Oxidative Cyclization of Acyclic Aryl-Substituted N-Vinylurethanes
Lenz, George R.,Costanza, Carl,Lessor, Ralph A.,Ezell, Edward F.
, p. 1753 - 1757 (2007/10/02)
Oxidation of the acyclic N-(1-(1-naphthyl)vinyl)urethane (3) with lead tetraacetate (LTA) forms a naphthyloxazolone as the major product, accompanied by the product of rearrangement, N-(ethoxycarbonyl)-1-naphthylacetamide.When the naphthyl group is replaced by alkoxy-substituted aromatic rings, the N-vinylurethane undergoes three successive oxidations by LTA leading to novel substituted nitrogen containing cyclic anhydrides, oxazolidine-2,5-diones.The structure of this unusual oxidation product was proven by X-ray analysis.The mechanism of the oxidation is discussed in terms of known enamide oxidations, and the intermediacy of an oxazolone is demonstrated.
