3246-80-8Relevant articles and documents
Kinetics of the hydride reduction of an NAD+ analogue by isopropyl alcohol in aqueous and acetonitrile solutions: Solvent effects, deuterium isotope effects, and mechanism
Lu, Yun,Qu, Fengrui,Zhao, Yu,Small, Ashia M. J.,Bradshaw, Joshua,Moore, Brian
, p. 6503 - 6510 (2009)
(Chemical Equation Presented) The rate constants of the hydride-transfer reactions from isopropyl alcohol (i-PrOH) to an NAD+ model, 9-phenylxanthyliumion (PhXn+), in acetonitrile (AN) and inwater containing AN (80% H2O/20% AN) were determined over a temperature range from 36 to 67°C. The reactions follow second-order rate laws. In the latter solution, formation of the water adduct of PhXn+ was observed as a side-equilibrium (K). The observed inverse solvent kinetic isotope effect (kH2Oobs/kD2Oobs = 0.54), the larger than unity equilibrium isotope effect (K(H2O)/K(D2O) = 2.69), and the results of acid effect on the observed rate constants of the reactions are consistent with the "side-equilibriummechanism". Kinetic isotope effects at all three H/D positions of i-PrOH for the net hydride-transfer process were determined in both solutions at 60°C: KIE α-DH = 3.2(AN), 3.2(H2O); KIE β-D6H = 1.05(AN), 1.16(H2O); KIE ODH = 1.08(AN), 1.04(H2O). These KIE values are consistent with the presence of the positively charged alcohol moiety in the transition state (TS) for cleavage of the α-C-H bond, the delocalization of the positive charge over the α-C-OH group, and the stepwise hydride and proton transfer processes. Comparison of the activation parameters for the reactions in the two solvent systems as well as those in the i-PrOH/AN (1:1 v/v) reported earlier suggests that the AN medium promotes the reaction by activating the ground-state alcohol reactant through weak interactions with the electron pairs on alcohol O, while water and parent alcohol media facilitate the reaction by H-bonding stabilization of the alcohol moiety of the TS. Results suggest that in the alcohol dehydrogenases without a Zn(II) cofactor in the active sites alcohols would be oxidized via hydride transfer to NAD+ coenzyme followed by the rapid deprotonation to the nearby basic species in the active site of the enzymes.
NaHSO4/SiO2catalyzed generation of: o -quinone/ o -thioquinone methides: synthesis of arylxanthenes/ arylthioxanthenes via oxa-6π-electrocyclization
Anthony, Savarimuthu Philip,Karthick, Muthupandi,Konikkara Abi, Edwin,Ramanathan, Chinnasamy Ramaraj,Someshwar, Nagamalla
, p. 8653 - 8667 (2020/11/17)
ortho-Quinone methides, very reactive transient intermediates, are utilized successfully in synthesizing complex organic molecules of natural and biological significance. Among several synthetic protocols, the acid catalyzed generation of ortho-quinone me
Copper-Catalyzed One-Pot Synthesis of Dibenzofurans, Xanthenes, and Xanthones from Cyclic Diphenyl Iodoniums
Zhu, Daqian,Li, Min,Wu, Zhouming,Du, Yongliang,Luo, Bingling,Huang, Peng,Wen, Shijun
, p. 4566 - 4571 (2019/07/09)
Oxygenation of cyclic diphenyl iodoniums (CDPIs) with varied medium-ring sizes has been fully investigated. This practical copper-catalyzed tandem reaction of CDPIs with water as the oxygen source enables the construction of derivatised dibenzofurans and xanthenes at moderate to good yields. Moreover, structurally important xanthones are also successfully accessed under the oxygenation conditions with additional TEMPO.
