Model Studies of Topaquinone-Dependent Amine Oxidases. 2. Characterization of Reaction Intermediates and Mechanism
摘要:
The reaction of 2-hydroxy-5-tert-butyl-1,4-benzoquinone (1a) and benzylamine in acetonitrile was studied under anaerobic conditions. Addition of benzylamine to the quinone 1a solution generates the anionic form of the quinone (lambda(max) at 492 nm), followed by the formation of the product Schiff base 11 with lambda(max) at 368 nm and the aminoresorcinol 13 with lambda(max) at 304 nm. The rapid dissociation of the 2-hydroxyl proton was confirmed by the isolation of the amine salt 5a in the reaction of tert-butylamine and 1a. The substrate Schiff base 6a was not spectrally detected due to its lower extinction coefficient and rapid conversion to the product Schiff base 11. However, when alpha-methylbenzylamine was employed as a substrate, the formation of the substrate Schiff base 7 was detected by H-1 NMR and W-vis spectroscopy, Cyclohexylamine, n-propylamine, and ammonia also gave the substrate Schiff bases 8, 9, and 10, respectively, Both the steric bulk and the acidity of the C-1 proton of the substrate are found to be factors controlling the further reaction (C-1 proton abstraction). Detailed structural analysis of the substrate Schiff base was performed on 8 by 2D NMR spectroscopy, showing that 8 is in its amine salt form and has undergone nucleophilic addition at C-1, the carbonyl carbon next to the 2-hydroxyl group. W-vis spectroscopy supports the view that 8 is not a solvent-separated ion pair (lambda(max) at 454 nm) but an intimate ion pair (lambda(max) at 352 nm) in CH3CN. The latter lambda(max) value is very similar to lambda(max) observed for the Schiff base complex seen in bovine serum amine oxidase and different from a Schiff base complex with 4-methoxy-5-tert-butyl-1,2-benzoquinone 14. The product Schiff base 11 was prepared by the reaction of the hydrochloride salt of the aminoresorcinol 13 and benzaldehyde. It has an epsilon value 10 times larger than that of the substrate Schiff base (7, 8, or 9) at 368 nm. Treatment of 11 with benzylamine yielded the aminoresorcinol 13 and the product, N-benzylidenebenzylamine (PhCH=NCH(2)Ph). Comparison of these results to catalytic properties of the copper amine oxidases provides support for an aminotransferase mechanism from a Schiff base of topa in a localized p-quinone form (B in Scheme 1).
Intermolecular N–H Oxidative Addition of Ammonia, Alkylamines, and Arylamines to a Planar σ<sup>3</sup>-Phosphorus Compound via an Entropy-Controlled Electrophilic Mechanism
作者:Sean M. McCarthy、Yi-Chun Lin、Deepa Devarajan、Ji Woong Chang、Hemant P. Yennawar、Robert M. Rioux、Daniel H. Ess、Alexander T. Radosevich
DOI:10.1021/ja412469e
日期:2014.3.26
Ammonia, alkyl amines, and aryl amines are found to undergo rapid intermolecular N-H oxidative addition to a planar mononuclear σ(3)-phosphorus compound (1). The pentacoordinate phosphorane products (1·[H][NHR]) are structurally robust, permitting full characterization by multinuclear NMR spectroscopy and single-crystal X-ray diffraction. Isothermaltitrationcalorimetry was employed to quantify the
Mechanistic Investigation of the Ruthenium-N-Heterocyclic-Carbene-Catalyzed Amidation of Amines with Alcohols
作者:Ilya S. Makarov、Peter Fristrup、Robert Madsen
DOI:10.1002/chem.201202400
日期:2012.12.3
The mechanism of the ruthenium–N‐heterocyclic‐carbene‐catalyzed formation of amides from alcohols and amines was investigated by experimental techniques (Hammett studies, kinetic isotope effects) and by a computational study with dispersion‐corrected density functional theory (DFT/M06). The Hammett study indicated that a small positive charge builds‐up at the benzylic position in the transition state
oligomers, previously unreported reactivity of the N-substituted disulfonimide functional group was discovered. Under basic conditions, unexpected lengthening of the oligomers occurs through a "transdisulfonimidation" reaction, whereby new disulfonimides are synthesized from existing ones by reaction with sulfonamide anion. This process appears to proceed via formation of a sulfene intermediate. Support for
the intermediate formation of the corresponding isocyanate, which, in turn, reacts further with a nucleophilic reagent also present in the mixture and results in carbamoylation with good yield. On the basis of this reaction a practical carbamoylation procedure was devised and a comparative study on suitability of different solvents and phosphorus (III) derivatives for carbamoylation reaction was conducted
Nucleophilic Substitution Reactions of N-Methyl α-Bromoacetanilides with Benzylamines in Dimethyl Sulfoxide
作者:Keshab Kumar Adhikary、Hai-Whang Lee
DOI:10.5012/bkcs.2011.32.3.857
日期:2011.3.20
:Benzylaminolysis, N-Methyl-α-bromoacetanilides, Cross-interaction constant, Deuterium kineticisotope effect, Biphasic nonlinear free energy correlationIntroductionIn a series of the nucleophilic substitutionreactions ofα-halocarbonyl compounds,
< 1) 对于 Y = 吸电子取代基。N-甲基-Y-α-溴乙酰苯胺的苄基氨基分解的机制是一种协同机制,具有五元环 TS,涉及 NH(D) 中的氢(氘)原子和 C = O 中的氧原子之间的氢键Y = 给电子,而与烯醇状 TS 的协同机制,其中亲核试剂攻击 α-碳以获得 Y = 吸电子取代基。关键词:苄氨解,N-甲基-α-溴乙酰苯胺,交叉相互作用常数,氘动力学同位素效应,双相非线性自由能相关介绍在α-卤代羰基化合物的一系列亲核取代反应中,