- Scope and mechanism of a true organocatalytic beckmann rearrangement with a boronic acid/perfluoropinacol system under ambient conditions
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Catalytic activation of hydroxyl functionalities is of great interest for the production of pharmaceuticals and commodity chemicals. Here, 2-alkoxycarbonyl- and 2-phenoxycarbonyl-phenylboronic acid were identified as efficient catalysts for the direct and chemoselective activation of oxime N-OH bonds in the Beckmann rearrangement. This classical organic reaction provides a unique approach to prepare functionalized amide products that may be difficult to access using traditional amide coupling between carboxylic acids and amines. Using only 5 mol % of boronic acid catalyst and perfluoropinacol as an additive in a polar solvent mixture, the operationally simple protocol features mild conditions, a broad substrate scope, and a high functional group tolerance. A wide variety of diaryl, aryl-alkyl, heteroaryl-alkyl, and dialkyl oximes react under ambient conditions to afford high yields of amide products. Free alcohols, amides, carboxyesters, and many other functionalities are compatible with the reaction conditions. Investigations of the catalytic cycle revealed a novel boron-induced oxime transesterification providing an acyl oxime intermediate involved in a fully catalytic nonself-propagating Beckmann rearrangement mechanism. The acyl oxime intermediate was prepared independently and was subjected to the reaction conditions. It was found to be self-sufficient; it reacts rapidly, unimolecularly without the need for free oxime. A series of control experiments and 18O labeling studies support a true catalytic pathway involving an ionic transition structure with an active and essential role for the boronyl moiety in both steps of transesterification and rearrangement. According to 11B NMR spectroscopic studies, the additive perfluoropinacol provides a transient, electrophilic boronic ester that is thought to serve as an internal Lewis acid to activate the ortho-carboxyester and accelerate the initial, rate-limiting step of transesterification between the precatalyst and the oxime substrate.
- Mo, Xiaobin,Morgan, Timothy D. R.,Ang, Hwee Ting,Hall, Dennis G.
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supporting information
p. 5264 - 5271
(2018/04/24)
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- ENAMIDE PROCESS
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A convenient method for converting oximes into enamides is disclosed. The process produces enamides without the concomitant production of a large volume of metallic waste. The enamides are useful precursors to amides and amines.
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Paragraph 0207; 0208
(2018/08/20)
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- Catalytic Enantio- and Diastereoselective Mannich Addition of TosMIC to Ketimines
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Chiral amines bearing a stereocenter in the α position are ubiquitous compounds with many applications in the pharmaceutical and agrochemical sectors, as well as in catalysis. Catalytic asymmetric Mannich additions represent a valuable method to access such compounds in enantioenriched form. This work reports the first enantio- and diastereoselective addition of commercially available p-toluenesulfonylmethyl isocyanide (TosMIC) to ketimines, affording 2-imidazolines bearing two contiguous stereocenters, one of which is fully-substituted, with high yields and excellent stereocontrol. The reaction, catalyzed by silver oxide and a dihydroquinine-derived N,P-ligand, is broad in scope, operationally simple, and scalable. Derivatization of the products provides enantioenriched vicinal diamines, precursors to NHC ligands and sp3-rich heterocyclic scaffolds. Computations are used to understand catalysis and rationalize stereoselectivity.
- Franchino, Allegra,Chapman, Jack,Funes-Ardoiz, Ignacio,Paton, Robert S.,Dixon, Darren J.
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supporting information
p. 17660 - 17664
(2018/11/10)
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- ANTIVIRAL OXIME PHOSPHORAMIDE COMPOUNDS
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Compounds of Formula I: I and their pharmaceutically acceptable salts are useful for the inhibition of HIV reverse transcriptase. The compounds may also be useful for the prophylaxis or treatment of infection by HIV and in the prophylaxis, delay in the onset or progression, and treatment of AIDS. The compounds and their salts can be employed as ingredients in pharmaceutical compositions, optionally in combination with other antiviral agents, immunomodulators, antibiotics or vaccines.
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Page/Page column 28; 29
(2017/07/06)
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- Optical activity 1-cyclohexyl ethylamine preparation method
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The present invention discloses an optical activity 1-cyclohexyl ethylamine preparation method, which comprises that: in water and under the effect of HBr, N-acetylamino-1-cyclohexyl ethylamine represented by a formula 4 or 4' is subjected to a hydrolysis reaction to correspondingly prepare the optical activity 1-cyclohexyl ethylamine represented by a formula 5 or 5'. The preparation method of the present invention can further comprise that a compound represented by a formula I is subjected to an oximation reaction, a reduction acylation reaction and an asymmetric catalysis reaction to prepare the N-acetylamino-1-cyclohexyl ethylamine represented by the formula 4 or 4'. According to the present invention, the preparation method has characteristics of simple operation, low production cost, high product chemical purity, high product optical purity, high product yield, and green environmental protection. The formulas such as 4, 4', 5 and 5' are defined in the specification.
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Paragraph 0059; 0075; 0076; 0077
(2016/10/08)
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- TETRAZOLINONE COMPOUND AND USE THEREOF
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The compound represented by formula (1): wherein R4 and R5 each represents a hydrogen atom, a halogen atom, or a C1-C3 alkyl group; R6 represents a C1-C4 alkyl group, a C3-C6 cycloalkyl group, or the like; R7, R8, and R9 each represents a hydrogen atom, a halogen atom, or the like; R10 represents a C1-C3 alkyl group, or the like; R13 represents a C1-C3 alkyl group, or the like; and Q represents a phenyl group, or the like; has an excellent control effect on pests.
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Paragraph 0878; 0908
(2015/11/16)
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- Bifunctional iminophosphorane organocatalysts for enantioselective synthesis: Application to the ketimine nitro-Mannich reaction
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The design, synthesis, and development of a new class of modular, strongly basic, and tunable bifunctional Bronsted base/H-bond-donor organocatalysts are reported. These catalysts incorporate a triaryliminophosphorane as the Bronsted basic moiety and are readily synthesized via a last step Staudinger reaction of a chiral organoazide and a triarylphosphine. Their application to the first general enantioselective organocatalytic nitro-Mannich reaction of nitromethane to unactivated ketone-derived imines allows the enantioselective construction of β-nitroamines possessing a fully substituted carbon atom. The reaction is amenable to multigram scale-up, and the products are useful for the synthesis of enantiopure 1,2-diamine and α-amino acid derivatives.
- Nunez, Marta G.,Farley, Alistair J. M.,Dixon, Darren J.
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supporting information
p. 16348 - 16351
(2013/12/04)
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- Acid hydrolysis of amides obtained by Beckmann rearrangement of methyl ketones oximes of unsaturated γ-lactone, aromatic, and alicyclic series
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Beckmann rearrangement was performed of oximes of substituted 3-acetyl-4-methyl-5,5-dimethyl(pentamethylene)-2-oxo-2,5-dihydrofuranes in the presence of boron trifluoride etherate. Aiming at establishing the spatial arrangement of the oximes the hydrolysis was carried out of acid amides obtained by Beckmann rearrangement of oximes of methyl ketones belonging to unsaturated γ-lactone series and also to aromatic and alicyclic series. The hydrolysis with 20% sulfuric acid led to the formation of the corresponding acid and amine, and the hydrolysis with acetic and hydrochloric acids resulted in retrobeckmann rearrangement giving the initial oximes.
- Tokmadzhyan
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experimental part
p. 1746 - 1749
(2012/03/10)
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- Facile and efficient enantioselective strecker reaction of ketimines by chiral sodium phosphate
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A facile and efficient enantioselective Strecker reaction of ketimines catalyzed by a chiral alkali-metal salt has been developed. When 10 mol% BNPNa (BNP=1,1'-binaphthyl-2,2'-diylphosphate) prepared in situ and 10 mol% para-tert-butylortho-adamantylphenol (PBAP) were introduced into the reaction, up to 96% yield and up to 95% ee (ee=enantiomeric excess) were obtained. Both aliphatic and aromatic ketimines, especially sterically bulky cyclic ketimines derived from β-acetonaphthone, α-indanone, and α-tetralone were found suitable for this reaction. On the basis of the experimental results and previous reports, trimethylsilyl cyanide (TMSCN) was indicated to be the real reactive nucleophile despite the existence of PBAP, and a possible working model was proposed to explain the origin of the asymmetric induction. The facile availability of 1,1'-binaphthyl-2,2'-diylphosphoric acid (BNPH) and the simplicity of the procedure are beneficial for practical applications.
- Shen, Ke,Liu, Xiaohua,Cai, Yunfei,Lin, Lili,Feng, Xiaoming
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supporting information; experimental part
p. 6008 - 6014
(2010/02/28)
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- Intermolecular Cope-type hydroamination of alkenes and alkynes using hydroxylamines
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The development of the Cope-type hydroamination as a method for the metal- and acid-free intermolecular hydroamination of hydroxylamines with alkenes and alkynes is described. Aqueous hydroxylamine reacts efficiently with alkynes in a Markovnikov fashion to give oximes and with strained alkenes to give N-alkylhydroxylamines, while unstrained alkenes are more challenging. N-Alkylhydroxy-lamines also display similar reactivity with strained alkenes and give modest to good yields with vinylarenes. Electron-rich vinylarenes lead to branched products while electron-deficient vinylarenes give linear products. A beneficial additive effect is observed with sodium cyanoborohydride, the extent of which is dependent on the structure of the hydroxylamine. The reaction conditions are found to be compatible with common protecting groups, free OH and NH bonds, as well as bromoarenes. Both experimental and theoretical results suggest the proton transfer step of the N-oxide intermediate is of vital importance in the intermolecular reactions of alkenes. Details are disclosed concerning optimization, reaction scope, limitations, and theoretical analysis by DFT, which includes a detailed molecular orbital description for the concerted hydroamination process and an exhaustive set of calculated potential energy surfaces for the reactions of various alkenes, alkynes, and hydroxylamines.
- Moran, Joseph,Gorelsky, Serge I.,Dimitrijevic, Elena,Lebrun, Marie-Eve,Bedard, Anne-Catherine,Seguin, Catherine,Beauchemin, Andre M.
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supporting information; experimental part
p. 17893 - 17906
(2009/07/18)
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- Homolytic C-Alkylation of Aldoximes
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Thermal decomposition of alkyl peresters in hydrogen donor solvents (cycloalkanes or ethers) in the presence of aldoximes affords (C-1)-alkylated products.The reaction is favored by electron-withdrawing substituents on the oxime and involves free C-radica
- Citterio, Attilio,Filippini, Lucio
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p. 473 - 474
(2007/10/02)
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- Wanderungstendenzen cyclischer, polycyclischer und methylverzweigter Alkylreste bei der Beckmann-Umlagerung
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The migration aptitudes of polycyclic bridgehead groups, cycloalkyl groups as well as of β-, γ- and δ-branched alkyl groups in the Chapman variant of the Beckmann rearrangement were determined.From these data it is concluded that at transition state 2 the migrating group is not resembling a planarised carbenium ion R+, but rather a pentacoordinated carbonium ion structure.Because only small geometrical changes occur in the migrating group vertical stabilisation of charge at transition state is believed to have significant influence on the migration aptitudes.
- Langhals, Heinz,Ruechardt, Christoph
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p. 3831 - 3854
(2007/10/02)
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