Reaction of the ambident electrophile dimethyl carbonate with the ambident nucleophile phenylhydrazine

To explore the ambident electrophilic reactivity of dimethyl carbonate (DMC), reactions with the ambident nucleophile phenylhydrazine were investigated. When a Br?nsted base was used, selective carboxymethylation occurred at N-1, after that several other compounds were produced selectively utilizing various conditions. Formation of these compounds was explained by using the Hard-Soft Acid-Base (HSAB) theory. Catalysis by some metal salts altered the reactivity of phenylhydrazine, which effected selective carboxymethylation at N-2 of phenylhydrazine instead.     

取代苯肼及其冠醚络合物光解行为的研究

冠醚金属离子络合物中，金属离子与配体间的静电作用是早已熟知的．后来发现一些中性分子如硝基苯胁、苯胺等亦能与冠醚形成络合物．硝基苯胁作为谈基试剂广泛用于有机化学研究，但由于其在有机溶剂中低的溶解度，一些苯晚的形成常常必须在高极性溶剂和高温下进行，从而导致一些不利的副反应．苯防与冠醚形成络合物后则可大大提高其在有机溶剂中的溶解度，并且还明显地改变其稳定性．由于这些络合物，主体与客体间的作用与生物体系中受体一基质络合物相似，其成键本质及络合物中客体性质的变化引起人们极大兴趣·1980年首次报导了苯时及取代…     

A Convenient Modification of the Fischer Indole Synthesis with a Solid Acid

A new one-pot version of the titled reaction involves heating a mixture of a carbonyl compound, a phenylhydrazine, and the cation exchange resin Amberlite IR 120 in refluxing ethanol. A variety of enolizable aldehydes, and ketones and several substituted phenylhydrazines could thus be converted to the corresponding indoles in excellent yields (70–88%). Reaction times were typically 6–10 h, with the resin being then filtered off and the product isolated after minimal workup.     

Neutral versus charged species in enzyme catalysis. Classical and free energy barriers for oxygen atom transfer from C4a-hydroperoxyflavin to dimethyl sulfide

Theoretical calculations at the B3LYP/6-31+G(d,p) level have been used to study the oxidation of dimethyl sulfide by a series of bicyclic and tricyclic model C4a-flavin hydroperoxides. The intrinsic gas-phase reactivity of tricyclic C4a-hydroperoxyflavin 4 is ca. 10(9) greater than t-BuOOH but is ca. 10(7) less reactive toward the oxidation of dimethyl sulfide than peroxyformic acid. The SN2-like attack of the nucleophile on the distal oxygen of the hydroperoxide and the relative reactivity of the peracid are in excellent agreement with the earlier experimental data of Bruice. The effect of N1 or N5 hydrogen-bonding interactions on the activation barriers for oxygen atom transfer have been examined. Classical energy barriers for oxygen atom transfer from neutral and ion-paired forms of C4a-hydroperoxyflavin to dimethyl sulfide are predicted to differ by a small margin, suggesting that proton distribution exerts a relatively small influence on the reactivity of alkyl hydroperoxides. Isolated N1- and N5-protonated cations exhibit artificially low barriers as a consequence of their location in a high energy region of the potential energy surface domain.     

The mass spectra of some simple phenylhydrazides and a re-examination of the fragmentations of phenylhydrazine

The elimination of small neutral fragments from acetyl-, formyl- and ethoxycarbonyl- phenylhydrazines with formation of [C6H8N2]⁺? ions has been studied. Evidence is obtained from deuterium labelling and from metastable peak intensity ratios, to show that ketene loss from both acetylphenylhydrazines is accompanied (or preceded) by hydrogen transfer to the acylated nitrogen atom to give ions structurally analogous to the phenylhydrazine molecular ion. The decomposing [C6H8N2]⁺? ions formed from formyl- and ethoxycarbonylphenylhydrazines are also suggested to have a phenylhydrazine-like structure. In the molecular ion of phenylhydrazine interchange occurs between the two ortho hydrogen atoms and two of the three hydrazine hydrogens prior to decomposition; labelling data suggest that the N-1 hydrogen does not participate in the interchange process.     

TDI和MDI洁净合成方法的研究进展

对甲苯二异氰酸酯（TDI）和二苯甲烷二异氰酸酯（MDI）的合成方法,尤其是用碳酸二甲酯（DMC）代替光气的洁净合成方法的研究进展进行了综述。重点讨论了反应所涉及到的催化剂体系及其反应性能。     

Tetrazole compounds. 10. Novel tetrazolylindoles by fischer indolization of substituted tetrazolylacetaldehyde phenylhydrazones

The acid-catalyzed reaction of substituted phenylhydrazines 1 with 1-aryl-5-(2-dimethylaminovinyl)-1H-tetrazoles 2 afforded (1-aryl-1H-tetrazol-5-yl)acetaldehyde phenylhydrazones 3 which on heating in acetic acid/perchloric acid underwent a Fischer indolization to give substituted 3-(1-aryl-1H-tetrazol-5-yl)-indoles 4a-k. Indoles of this type are also formed on subjecting 1 and 2 directly to indolization conditions; thus, starting from phenylhydrazine the tetrazolylindoles 41-s were obtained by a one-pot procedure. Indolization of corresponding N_α-methylphenylhydrazones 5 resulted in 1-methyl-3-(1-aryl-1H-tetrazol-5-yl)indoles 6 .     

Abraham model enthalpy of solvation correlations for solutes dissolved in dimethyl carbonate and diethyl carbonate

Experimental data have been compiled from the published chemical and engineering literature on the enthalpies of solvation for 80 different inorganic gases and organic vapours in diethyl carbonate and for 57 different gaseous compounds in dimethyl carbonate. The compiled data are used to derive mathematical correlations based on the Abraham solvation parameter model. The derived expressions describe the experimental solvation enthalpies in diethyl carbonate and dimethyl carbonate to within standard deviations of 2.1 and 2.7 kJ mol^?1, respectively.     

Change in the reactivity of N-vinylsuccinimide after complexation with dimethyl sulfoxide

The influence of dimethyl sulfoxide on the copolymerization kinetics and the reactivity parameters of N-vinylsuccinimide was studied. It was shown that, owing to the complexation of monomer molecules with dimethyl sulfoxide molecules, the relative activities of monomers are changed. The electron structures of N-vinylsuccinimide and dimethyl sulfoxide molecules and the molecule geometry was considered, and a complexation mechanism was proposed. The Alfrey–Price Q-e parameters of N-vinylsuccinimide during the complexation were analyzed. The causes of the change in the reactivity of monomer were revealed.     

绿色工艺的原料--碳酸二甲酯

比较系统地综述了碳酸二甲酯的性质及合成工艺情况,并对碳酸二甲酯的应用作了分析。介绍了碳酸二甲酯制备的技术及应用研究的最新情况,对碳酸二甲酯在我国的发展作了展望。     

Preparation of Dodecyl Dimethyl Benzyl Ammonium Bromide-Doped Cubic CaCO<Subscript>3</Subscript> with Antibacterial Properties

CaCl₂ encapsulated was placed in the hydrothermal reactor of an aqueous solution of Na₂CO₃ and dodecyl dimethyl benzyl ammonium bromide for synthesis of two samples of calcium carbonate by an improved hydrothermal method and one-pot method. Their crystal structure, morphology, chemical composition, and thermal stability of the synthesized samples of calcium carbonate were investigated by XRD, FTIR, SEM, EDS and TGDSC. The sterilization activity of the as-prepared samples was evaluated by killing of Sarcina lutea bacteria. The results indicated that the regular cube capsule-assisted calcium carbonate prepared by hydrothermal process was doped with dodecyl dimethyl benzyl ammonium bromide. Under the same condition, the spindle-shaped calcium carbonate synthesized the one-pot method was not doped with dodecyl dimethyl benzyl ammonium bromide. Among the samples of calcium carbonate, capsule-assisted calcium carbonate had shown better antibacterial effect for Sarcina lutea: in 48 h after its inhibition a zone diameter was 12.3 mm.     

Selective N-monomethylation of primary anilines with dimethyl carbonate in continuous flow

Selective N-monomethylation of anilines has been achieved under continuous flow conditions using dimethyl carbonate as a green methylating agent in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene. Our methodology takes advantage of the expanded process windows available in the continuous flow regime to safely induce monomethylation in superheated solvents at high pressure. We propose selective N-monomethylation is achieved via an in situ protection-deprotection pathway, which is supported by the observed reactivities of several putative reaction intermediates. The robust and scalable method was applicable to a broad range of primary aniline substrates including ortho-, meta-, and para-substituted anilines, as well as electron-rich and electron-deficient anilines. The synthetic precursor of diazepam, 5-chloro-2-(methylamino)benzophenone, was selectively synthesized under our optimized conditions.     

A convenient procedure for smooth palladium-catalyzed allylic alkylation by sodium dimethyl malonate and cyclopentadienide. A new synthesis of allylic substituted cyclopentadienes.

The use of the Pd(dba)¹₂/dpe catalytic system in allylic alkylation allows sodium dimethyl malonate to react with allylic acetates at room temperature. According to this procedure, a novel synthesis of allylic substituted cyclopentadienes is described through the use of cyclopentadienide anion as a nucleophile.     

Simple d-glucosamine-based phosphine-imine and phosphine-amine ligands in Pd-catalyzed asymmetric allylic alkylations

A new family of phosphine-imine and phosphine-amine ligands based on d-glucosamine were synthesized in order to probe previous asymmetric allylic alkylation results with those of disaccharide ligands of the same class. In most cases, good-to-excellent activities and enantioselectivies were observed with these ligands with ee’s reaching up to 87% in the Pd-catalyzed allylic alkylation reaction of racemic (E)-1,3-diphenyl-2-propenyl acetate with dimethyl malonate as the nucleophile.     

Electrochemistry of chalcogenoglycosides. Rational design of iterative glycosylation based on reactivity control of glycosyl donors and acceptors by oxidation potentials

Electrochemical properties of various para-substituted phenylthio-, phenylseleno-, and phenyltelluroglucopyranosides bearing acetyl, benzoyl, and benzyl protecting groups have been investigated to estimate the reactivity of chalcogenoglycosides toward electrochemical glycosylations. The oxidation potential of the chalcogenoglycosides shows good correlation with the ionization potential of chalcogen atoms, and decreases in the order thio-, seleno-, and telluroglycosides. It is also affected by the para-substituents, and the substitution effect correlates very well with the HOMO energy of para-substituted benzenechalcogenol and with the Hammett sigma p + value. Electrochemical glycosylation of telluroglycosides has been examined, and it was found that the use of an undivided cell is more effective than the use of a divided cell. Selective activation of the chalcogenoglycosides in bulk electrolysis based on their oxidation potentials has been examined, and the relative reactivity of the telluroglycosides can be estimated from their oxidation potentials. However, the relative reactivity of selenoglycosides in the preparative glycosylation was rather insensitive to the oxidation potential values.     

UV-light induced photodegradation of bisphenol a in water: Kinetics and influencing factors

The synthesis of dimethyl carbonate (DMC) from methanol and ethylene carbonate (EC) without using any solvent was investigated in the presence of ionic liquids as catalysts. The conversion of ethylene carbonate was affected by the structure of ionic liquid. For a series of 1-alkyl-3-methylimidazolium ionic liquids, the one with shorter alkyl chain and the one with more nucleophilic anion showed higher reactivity. The conversion of EC also increased with CO₂ pressure and reaction temperature. Esterification of EC and methanol can be considered as a pseudo-first order reaction with respect to EC concentration. The activation energy was estimated as 50.1 kJ/mol.     

Protic ionic liquid-promoted synthesis of dimethyl carbonate from ethylene carbonate and methanol

In this work,the protic ionic liquid[DBUH][Im](1,8-diazabicyclo[5.4.0]-7-undeceniumimidazolide)was developed as an efficient catalyst for the transesterification of ethylene carbonate with methanol to produce dimethyl carbonate.At 70℃,up to 97%conversion of ethylene carbonate and 91%yield of dimethyl ca rbonate were obtained with 1 mol%[DBUH][Im](relative to ethylene carbonate)as catalyst in 2 h.Even at room temperature,the conversion of ethylene carbonate can reach 94%and the yield of dimethyl carbonate can approach 81%for 6 h.Catalytic mechanism investigation showed the high catalytic efficiency of this ionic liquid results from the synergistic activation effect,wherein the cation can activate ethylene carbonate and the anion can activate methanol through hydrogen bond formatio n.Although the reusability of the ionic liquid need to be further improved,high efficiency and comme rcial availability of[DBUH][Im]render it a promising catalyst for the preparation of dimethyl carbonate.     

Interaction of methanol,methanthiol, and acetoxime with potassium and rubidium hydroxides in dimethyl sulfoxide

An ab initio quantum chemical study of the reaction profiles of the nucleophile particle formation in the interaction of methanol, methanthiol, and acetoxime with an undissociated molecule of alkali metal hydroxide is performed for the gas phase and also with the explicit inclusion of a dimethyl sulfoxide molecule into the calculation and with allowance made for solvation effects within the continuum model.     

Predicting the reactivity of ambidentate nucleophiles and electrophiles using a single, general-purpose, reactivity indicator

We recently proposed a new reactivity indicator, termed the "general-purpose reactivity indicator", Xi, which describes not only the classical reactivity paradigms, but also describes reactions that are neither frontier-orbital nor electrostatically controlled. This indicator was proposed to be especially useful for reactants with multiple reactive sites, especially if the nature of the reactivity at those sites was different. This suggests that this reactivity indicator is especially appropriate for ambidentate molecules; this paper confirms this hypothesis. The general-purpose reactivity indicator not only identifies the most reactive sites, it also identifies which substrates prefer which reactive sites. In particular, the reactivity indicator allows one to clearly distinguish which sites of an ambidentate molecule are most reactive when electron transfer from the attacking reagent is large (a soft reagent) and which sites are most reactive when the attacking reagent is hard and highly charged (so that electron transfer is relatively insignificant). To illustrate the efficacy of the indicator for nucleophiles we consider SCN(-), SeCN(-), NO(2)(-), SO(3)(2-). For electrophiles we consider dimethyl carbonate, N-methyl-N-nitrosotoluene-p-sulfonamide (MNTS), and 1-chloro-2,4,6-trinitrobenzene (CNB).