947-91-1Relevant articles and documents
Diphenylacetaldehyde and Its Enol: Determination of the Keto-Enol and Hydration Equilibrium Constants and the pKa's of the Aldehyde, Enol, and Hydrate. Comparison with Sterically Hindered System
Chiang, Y.,Kresge, A.J.,Krogh, E.T.
, p. 2600 - 2607 (1988)
The enol isomer of diphenylacetaldehyde was generated in aqueous solution from its potassium salt, formed by treating the aldehyde, with potassium hydride, and rates of ketonization of this enol were measured at 25 deg C in perchloric acid and sodium hydroxide solutions and acetic acid and bicarbonate ion buffers.These data, coupled with rates of enolization of the aldehyde measured at 25 deg C in acetic acid buffer and sodium hydroxide solutions, lead to duplicate independent determinations of the keto-enol equilibrium constant, , , the acid dissociation constant of the enol ionizing as an oxygen acid, , , and the acid dissociation constant of the aldehyde ionizing as a carbon acid, , .The equilibrium constant for formation of the aldehyde hydrate, Kh=4.7+/-0.2, was also determined by two independent methods, and the acid dissociation constant of the hydrate ionizing as an oxygen acid, , , was evaluated from kinetic data.The unusually large values of KE and for this system are attributed to stabilization of the carbon-carbon double bonds of the enol and enolate ion by the phenyl substituents.Comparison with literature data on sterically hindered, stable, "Fuson" enols bearing mesityl substituents suggests that a substantial portion of the thermodynamic stability of Fuson enols is provided by similar phenyl group stabilization of their double bonds; the methyls of the mesityl substituents of Fuson enols, however, do appear to play a critical role in conferring kinetic stability upon these substances.
Palladium-Catalyzed Allenamide Carbopalladation/Allylation with Active Methine Compounds
Zhu, Xiaoyi,Li, Ruibo,Yao, Hequan,Lin, Aijun
, p. 4630 - 4634 (2021/06/28)
A palladium-catalyzed allenamide carbopalladation/allylation with active methine compounds has been developed. Various indoles and isoquinolinones bearing a quaternary carbon center were achieved with good efficiency, a broad substrate scope and good functional group tolerance. This reaction underwent cascade oxidative addition, carbopalladation, and allylic alkylation, and two new C-C bonds were formed in one pot.
Competition Between Cα-S and Cα-Cβ Bond Cleavage in β-Hydroxysulfoxides Cation Radicals Generated by Photoinduced Electron Transfer?
Lapi, Andrea,D'Alfonso, Claudio,Del Giacco, Tiziana,Lanzalunga, Osvaldo
, p. 1310 - 1321 (2021/06/07)
A kinetic and product study of the 3-cyano-N-methyl-quinolinium photoinduced monoelectronic oxidation of a series of β-hydroxysulfoxides has been carried out to investigate the competition between Cα-S and Cα-Cβ bond cleavage within the corresponding cation radicals. Laser flash photolysis experiments unequivocally established the formation of sulfoxide cation radicals showing their absorption band (λmax ≈ 520?nm) and that of 3-CN-NMQ? (λmax ≈ 390?nm). Steady-state photolysis experiments suggest that, in contrast to what previously observed for alkyl phenyl sulfoxide cation radicals that exclusively undergo Cα-S bond cleavage, the presence of a β-hydroxy group makes, in some cases, the Cα-Cβ scission competitive. The factors governing this competition seem to depend on the relative stability of the fragments formed from the two bond scissions. Substitution of the β-OH group with -OMe did not dramatically change the reactivity pattern of the cation radicals thus suggesting that the observed favorable effect of the hydroxy group on the Cα-Cβ bond cleavage mainly resides on its capability to stabilize the carbocation formed upon this scission.
A Bifunctional Iron Nanocomposite Catalyst for Efficient Oxidation of Alkenes to Ketones and 1,2-Diketones
Ma, Zhiming,Ren, Peng,Song, Tao,Xiao, Jianliang,Yang, Yong,Yuan, Youzhu
, p. 4617 - 4629 (2020/05/19)
We herein report the fabrication of a bifunctional iron nanocomposite catalyst, in which two catalytically active sites of Fe-Nx and Fe phosphate, as oxidation and Lewis acid sites, were simultaneously integrated into a hierarchical N,P-dual doped porous carbon. As a bifunctional catalyst, it exhibited high efficiency for direct oxidative cleavage of alkenes into ketones or their oxidation into 1,2-diketones with a broad substrate scope and high functional group tolerance using TBHP as the oxidant in water under mild reaction conditions. Furthermore, it could be easily recovered for successive recycling without appreciable loss of activity. Mechanistic studies disclose that the direct oxidation of alkenes proceeds via the formation of an epoxide as intermediate followed by either acid-catalyzed Meinwald rearrangement to give ketones with one carbon shorter or nucleophilic ring-opening to generate 1,2-diketones in a cascade manner. This study not only opens up a fancy pathway in the rational design of Fe-N-C catalysts but also offers a simple and efficient method for accessing industrially important ketones and 1,2-diketones from alkenes in a cost-effective and environmentally benign fashion.
