- In Situ Generated Cobalt Catalyst for the Dehydrogenative Coupling of Alcohols and Amines into Imines
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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.
- Bottaro, Fabrizio,Madsen, Robert
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- Development and mechanistic investigation of the manganese(iii) salen-catalyzed dehydrogenation of alcohols
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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.
- Samuelsen, Simone V.,Santilli, Carola,Ahlquist, M?rten S. G.,Madsen, Robert
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p. 1150 - 1157
(2019/02/03)
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- Molybdenum-Catalyzed Dehydrogenative Synthesis of Imines from Alcohols and Amines
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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.
- Azizi, Kobra,Madsen, Robert
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p. 3703 - 3708
(2018/07/31)
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- A metallopeptoid as an efficient bioinspired cooperative catalyst for the aerobic oxidative synthesis of imines
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Enzymatic catalysis is largely based on intramolecular cooperativity between a metal center and functional organic molecules located on one scaffold. Inspired by this concept we have designed the metallopeptoid trimer BT, which is a unique intramolecular cooperative oxidation catalyst incorporating two catalytic centers, phenanthroline-copper and TEMPO, as well as one non-catalytic benzyl group. Herein we explore the capability of BT to act as an efficient catalyst for the oxidative synthesis of imines, which are versatile intermediates in the fine chemicals and pharmaceutical industries. We demonstrate that BT, combined with CuI, can catalyze the production of benzyl, aryl, heteroaryl, allylic and aliphatic imines from various alcohols and amines with a turn-over-number up to 45 times higher than this achieved when phenanthroline, copper and TEMPO are mixed in solution. Moreover, in low catalyst(s) loading, BT enables transformations that are not possible when a mixture of the individual catalysts is employed.
- Chandra Mohan, Darapanani,Sadhukha, Arghya,Maayan, Galia
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p. 139 - 144
(2017/10/16)
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- An investigation towards the diastereoselective synthesis of 3-acetoxy/methoxy/phthalimido-β-lactams using chiral imines
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The efficient diastereoselective synthesis of 3-acetoxy/methoxy/phthalimido-β-lactams 2/2′, 3/3′ and 4/4′ respectively was performed using chiral imines 1 obtained from chiral amines. Factors (solvent, temperature, substituent, steric bulk) influencing th
- Bhalla, Aman,Modi, Garima,Bari,Kumari, Anu,Narula, Dipika,Berry, Shiwani
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p. 307 - 316
(2017/02/18)
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- Dehydrogenative synthesis of imines from alcohols and amines catalyzed by a ruthenium N-heterocyclic carbene complex
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A new method for the direct synthesis of imines from alcohols and amines is described where hydrogen gas is liberated. The reaction is catalyzed by the ruthenium N-heterocyclic carbene complex [RuCl2(IiPr)(p-cymene)] in the presence of the ligand DABCO and molecular sieves. The imination can be applied to a variety of primary alcohols and amines and can be combined with a subsequent addition reaction. A deuterium labeling experiment indicates that the catalytically active species is a ruthenium dihydride. The reaction is believed to proceed by initial dehydrogenation of the alcohol to the aldehyde, which stays coordinated to ruthenium. Nucleophilic attack of the amine affords the hemiaminal, which is released from ruthenium and converted into the imine.
- Maggi, Agnese,Madsen, Robert
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experimental part
p. 451 - 455
(2012/04/23)
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- Method For The Preparation Of Cinacalcet And Intermediates And Impurities Thereof
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A method for the preparation of Cinacalcet is disclosed comprising treating (R)-1-naphthyl ethylamine with an aromatic aldehyde to form (1R)-1-(2-naphthyl)-N-(aryl methylene)ethanamine derivative of Formula (IV), which is further treated with 1-(3-halopropyl)-3-(trifluoromethyl)benzene of Formula (V) to obtain an iminium salt of Formula (VI), followed by hydrolysis to obtain Cinacalcet free base.
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Page/Page column 17
(2012/01/13)
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- Industrial application of the forster reaction: Novel one-pot synthesis of cinacalcet hydrochloride, a calcimimetic agent
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Described is a new, practical, and one-pot process, based on the Forster reaction, for the synthesis of cinacalcet hydrochloride (1), a calcimimetic agent and calcium-sensing receptor antagonist. The synthesis comprises the condensation of (1R)-(+)-1-naphthylethyl amine (2) with benzaldehyde (3) followed by reaction of obtained Schiff's base 4 with 1-(3-halopropyl)-3- (trifluoromethyl)benzene (5) to provide highly unstable iminium salt 6. Subsequent hydrolysis of 6 with water in the same pot yielded cinacalcet. The treatment of cinacalcet with hydrochloric acid during the workup process furnished 1 with an overall yield of around 60%. Our synthetic approach for 1, discussed in this report demonstrates industrial application of the century-old, unexplored name reaction, "Forster's Reaction" or Forster-Decker synthesis.
- Shinde, Gorakshanath B.,Niphade, Navnath C.,Deshmukh, Shrikant P.,Toche, Raghunath B.,Mathad, Vijayavitthal T.
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experimental part
p. 455 - 461
(2012/05/19)
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- A NEW METHOD FOR THE PREPARATION OF CINACALCET AND NEW INTERMEDIATES THEREOF
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A new method for the preparation of Cinacalcet by treating (R)-1-naphthyl ethylamine with an aromatic aldehyde to form (1R)-1-(2-naphthyl)-N-(aryl methylene)ethanamine derivative which is further treated with 1 -(3-hdopropyl)-3-(triflupromethyl) benzene of formula (V) to obtain an iminium salt and followed by hydrolysis to obtain Cinacalcet free base. A new compound, (1R)- I-(2-naphthyl)-N-(aryhnethylene)ethanamine, of formula (IV) and an iminium salt compound of formula (VI) are disclosed. which are intermediates for the preparation of Cinacalcet.
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Page/Page column 18
(2010/10/03)
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- Stereoselective oxidative addition of methyl iodide to chiral cyclometallated platinum(II) compounds derived from (R)-(+)-1-(1-naphthylethylamine). Crystal structure of [PtMe{3-(R)-(C10H7)CHMeNCHC4H 2S}PPh3]
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The reaction of 3-(R)-(C10H7)CHMeNCHC4H3S (2a) with [Pt2Me4(μ-SMe2)2] in acetone gave the new chiral cyclometallated platinum(II) compound [PtMe{3-(R)-(C10H7)CHMeNCHC4H 2S}SMe2] (3a). Addition of PPh3 produced compound [PtMe{3-(R)-(C10H7)CHMeNCHC4H 2S}PPh3] (4a) which was characterized by X-ray diffraction methods. While oxidative addition of methyl iodide to 3a gave two pairs of diastereomers, the analogous reaction for 4a produced only one diastereomer of the platinum(IV) compound [PtMe2I{3-(R)-(C10H7)CHMeNCHC4H 2S}PPh3] (7a). Subsequent isomerization of the resulting platinum(IV) compound gave a new pair of diastereomers in relative amounts 90 and 10%. Analogous proportions of final diastereomers were obtained for the oxidative addition of methyl iodide to the new chiral compounds [PtMe{3-(R)-(C10H7)CHMeNCHAr}PPh3] (Ar=C6H4 (4b), 2-FC6H3 (4c), 2-CF3C6H3 (4d)). The reaction of [Pt2Me4(μ-SMe2)2] with imines (R)-(C10H7)CHMeNCH(2-BrC6H4) (2e) and (R)-(C10H7)CHMeNCH(2,6-Cl2C6H 3) (2f) produced intramolecular oxidative addition to yield platinum(IV) compounds with some degree of stereoselectivity.
- Anderson, Craig,Crespo, Margarita,Rochon, Fernande D.
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p. 164 - 174
(2007/10/03)
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