117-34-0Relevant articles and documents
Kinetics and Mechanisms of the Reactions of Ketenes with Water and Alcohols in Dioxane Solutions
Poon, Nai L.,Satchell, Derek P.N.
, p. 1485 - 1490 (1986)
The spontaneous addition of water to diphenyl- and to dimethyl-ketene in dioxane-H2O and dioxane-D2O mixtures is third order in the stoicheiometric water concentration, s, when s H2O/kD2O = 1.7-2.3 for all the systems studied.The addition of ethanol to diphenylketene in dioxane-ethanol mixtures has a kinetic pattern very similar to that for addition of water to this ketene, except that the change to a lower order occurs when s = 5M.The variation of the activation parameters with medium composition is also very similar for all these spontaneous additions: at low water or ethanol concentrations Ea = 1+/- 1 kcal mol-1, and ΔS++ = -60 +/- 8 cal K-1 mol-1; at higher concentrations Ea rises somewhat, and ΔS++ becomes less negative.The results are considered in the light of previous work.It is concluded that water and alcohol add to ketenes by a common mechanism in non-hydroxylic solvents of low dielectric constant, and that this involves a cyclic, hydrogen-bonded transition state such as (1).Hydroxide ions (ca. 5*1E-3M) have no effect on the rate of water addition in dioxane, but hydrogen ions have powerful effects: the addition to diphenylketene is inhibited, that to dimethylketene is catalysed.These observations are explained.The isotope effect kH3O+/kD3O+ = 1.9 for the catalysis.We propose a catalytic mechanism with a cyclic transition state (3) involving a dominant slow proton transfer to the ketene β-carbon atom.
A Comparison of the Mechanism of Hydrolysis of Diphenylketene and Dimethylketene in Diethyl Ether Solution
Poon, Nai L.,Satchell, Derek P. L.
, p. 1381 - 1383 (1983)
The spontaneous hydrolysis of diphenylketene in diethyl ether solution at 25 deg C is first order in the ketene concentration and third order in the stoicheiometric water concentration; unlike the hydrolysis of dimethylketene, it is not-auto-catalytic and hydrolysis is negligibly catalised by added carboxylic acids.Added boron trifluoride strongly inhibits the hydrolysis of diphenylketene in ether but powefully catalyses that of dimethylketene; the formation of the strong Broensted acid H2OBF3 (association constant K = 120 +/- 20 l mol-1 at 25 deg C) underlines these effects.A pKa value of ca. 0.5 is deduced for this acid and the results as a whole point to the marked inability of diphenylketene , compared with dimethylketene, to accept protons from Broensted acids.Predominantly nucleophilic attack on the ketene is, however, easier for the diphenyl-derivative whose spontaneous hydrolysis varies between ca. 5- and ca. 40-fold faster over the range of stoicheoimetric water concentrations used.
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Seidel,Stoll
, p. 1830,1840 (1959)
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COBALT-CATALYZED SYNTHESIS OF α-ARYLPROPIONIC AND DIARYLACETIC ACIDS
Francalanci, F.,Gardano, A.,Foa, M.
, p. 277 - 282 (1985)
The cobalt-catalyzed carbonylation of ArCH(R)X (R=CH3, C6H5; X=Cl, Br) in alcoholic solvents under atmospheric pressure of CO is reported.Selective, high yield synthesis of the corresponding acids ArCH(R)COOH can be achieved within a very narrow range of experimental conditions by controlling kinetically the reversible interconversion of intermediate aryl and alkylcobalt complexes.The important roles of the base and of the alcoholic medium are briefly discussed.
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Fritsch,Feldmann
, p. 77 (1899)
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"Absolute" Asymmetric Synthesis Using the Chiral Crystal Environment: Photochemical Hydrogen Abstraction from Achiral Acyclic Monothioimides in the Solid State
Sakamoto, Masami,Takahashi, Masaki,Shimizu, Motoki,Fujita, Tsutomu,Nishio, Takehiko,et al.
, p. 7088 - 7089 (1995)
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Synthesis of l -octaarginine through microencapsulated palladium-catalyzed allyl ester deprotection
Pérez-López, Ana M.,González-Calderón, Dávir,Occorso, Antonio,Galindo-ángel, Javier,Domínguez-Seglar, José F.,Tamayo, Juan A.,Díaz-Gavilán, Mónica,Gómez-Vidal, José A.
, p. 2319 - 2322 (2014)
Octaarginine has been described as a molecular transporter. We report a useful synthesis of orthogonally protected l-octaarginine by using a method based on a microencapsulated palladium catalyst. Known palladium-based methods for allyl ester deprotection have been modified to facilitate purification of the unprotected intermediates. This improvement in the purification step has also been tested with a variety of allyl α-amino esters and allyl α,β-unsaturated esters.
X-ray crystallographic studies and comparative reactivity studies of a sodium diisopropylamide (NDA) complex and related hindered amides
Andrews, Philip C.,Barnett, Nicholas D.R.,Mulvey, Robert E.,Clegg, William,O'Neil, Paul A.,Barr, Donald,Cowton, Lucy,Dawson, Andrea J.,Wakefield, Basil J.
, p. 85 - 95 (1996)
Two related sodium amide complexes derived from secondary amines with bulky organic substituents have been synthesised and crystallographically characterised. Both [(iPr)2NNa(TMEDA)]2 and [Cy(iPr)NNa(TMEDA)]2 adopt dimeric crystal structures with a central, planar (nitrogen-metal)2 azametallocycle, a now familiar feature in both lithium amide and sodium amide chemistry. TMEDA ligands chelate in their usual bidentate manner making the Na+ cations four-coordinate with a distorted tetrahedral geometry. In the latter complex, the amido substituents are disposed in a trans conformation with respect to the (NNa)2 ring plane. The deprotonating ability of the former complex has been tested against that of the parent amide [(iPr)2NNa]∞ and the lithium congener [(iPr)2NLi]∞ (LDA) in a series of simple organic reactions: selective enolate formation from 2-octanone and 2-methylcyclohexanone; synthesis of diphenylacetic acid via diphenylmethane. In general, the performance of the sodium reagents compares favourably with that of the lithium reagent.
Desulfonylative Electrocarboxylation with Carbon Dioxide
Zhong, Jun-Song,Yang, Zi-Xin,Ding, Cheng-Lin,Huang, Ya-Feng,Zhao, Yi,Yan, Hong,Ye, Ke-Yin
supporting information, p. 16162 - 16170 (2021/09/02)
Electrocarboxylation of organic halides is one of the most investigated electrochemical approaches for converting thermodynamically inert carbon dioxide (CO2) into value-added carboxylic acids. By converting organic halides into their sulfone derivatives, we have developed a highly efficient electrochemical desulfonylative carboxylation protocol. Such a strategy takes advantage of CO2as the abundant C1 building block for the facile preparation of multifunctionalized carboxylic acids, including the nonsteroidal anti-inflammatory drug ibuprofen, under mild reaction conditions.
Metal Free, Direct and Selective Deoxygenation of α-Hydroxy Carbonyl Compounds: Access to α,α-Diaryl Carbonyl Compounds
Kumar, Anil,Sandeep,Venugopalan, Paloth
, (2020/04/27)
An efficient, metal free, direct and selective deoxygenation of α-hydroxy carbonyl compounds is achieved with the aid of catalytic amount of aqueous HClO4 (70 %) and triethylsilane as hydride source. A variety of α-hydroxy-α,α-diaryl carbonyl compounds are selectively deoxygenated to give α,α-diaryl carbonyl compounds in good to excellent yields. Intermediacy of α-keto carbenium ion is proposed on the basis of some control experiments and atmospheric pressure chemical ionization mass spectral analysis.