Graft copolymerization of methyl methacrylate to poly(vinyl alcohol) initiated by ferric ion-hydrogen peroxide system

The reaction occurring on treatment of samples of poly(vinyl alcohol) previously oxidized by sodium hypochlorite with ferric ion and hydrogen peroxide was studied. The graft copolymerization taking place on adding methyl methacrylate to the above system was also studied. Early in the reaction there was a period during which hydrogen peroxide was greatly reduced by the poly(vinyl alcohol), and this corresponded with a rapid cleavage reaction of the main chain of the polymer. Moreover, it was found that the reaction was quantitatively proportional to the formation of carbonyl groups in the sample. On the other hand, very few grafts were scarcely formed during this period; they formed by a mild reaction which took place immediately after this period. It seems that this behavior is quite different from that observed with the ceric ion initiating system. It is presumed that the formation of grafts is due to radicals formed by the cleavage of the main chain, and that the structure of the copolymer so formed is something like a block polymer.     

RhCo双金属催化剂的研究III. Rh+Co/Al2O3上表面羰基氢化物及其动态行为

利用连续流动微反研究了Rh+Co/Al2O3催化剂的CO加氢反应, 结果表明反应在220℃以上发生, 反应活性随着温度的升高和H2/CO值的增加而增加。利用TP-IR动态方法研究了Rh+Co/Al2O3上CO和H2共吸附及其动态行为。结果表明在Rh+Co/Al2O3的孪生及线式中心上, CO和H2室温共吸附时即有部分孪生及线式CO转化为相应的羰基氢化物, 随着温度的升高, 剩余的孪生和线式CO继续向相应的羰基氢化物转化。而羰基氢化物则向多羰基氢化物转化。在到达反应温度之前, 催化剂表面只存在羰基氢化物及相应的多氢羰基氢化物。在反应温度则导致产物CH4生成。与CO加氢反应和CO歧化的吸附态研究结果相关联, 作者认为Rh+Co/Al2O3上CO加氢生成CH4是经由羰基氢化物-多氢羰基氢化物途径。     

Reactivity of the 4-amino-5H-1,2-oxathiole-2,2-dioxide heterocyclic system: a combined experimental and theoretical study

The reactivity of the 4-amino-5H-1,2-oxathiole-2,2-dioxide (or beta-amino-gamma-sultone) heterocyclic system has scarcely been studied. Here we describe the reactivity of this system towards electrophiles and amines on readily available model substrates differently substituted at the C-5 position. A variety of C-electrophiles, carbonyl electrophiles (such as acyl chlorides, isocyanates, or aldehydes) and halogen or nitrogen electrophiles have been explored. Both the C-3 and 4-amino positions of the beta-amino-gamma-sultone system are able to undergo electrophilic reactions, and the reaction products depend on the electrophile used and on the reaction conditions. On the other hand, nucleophilic attack of amines occurs at the C-4 position of the beta-amino-gamma-sultone system only in spiranic substrates bearing alicyclic substituents at the C-5 position. A comparative computational study between spiranic and non-spiranic substrates suggests that conformational changes, undergone on intermediate compounds, account for the observed reactivity differences. Moreover, these conformational changes seem to bring about an increase of electron density on the N-4 and C-3 atoms of the enaminic system, and a possible enhancement in the reactivity of spiranic substrates towards electrophiles in the presence of amines. Experimental data consistent with this predicted enhanced reactivity is also presented.     

Chloracylierung und Bromacylierung von Carbonylverbindungen. IV. Bildungsmechanismus von Carbonsäure-(1-halogenalkyl)estern

Chloroacylation and bromoacylation of carbonyl compounds IV. Investigations of the reaction mechanism The kinetics of the Lewis acid catalyzed reaction between acyl chlorides and carbonyl compounds (especially aldehydes) is investigated by ¹H-NMR.-spectroscopy. With acetyl chloride as starting material a second order reaction is observed; the rate of the reaction increases in polar solvents as well as with increasing electron-donating capacity of the aldehyde. - With benzoyl chloride as starting material the reaction is first order with respect to benzoyl chloride, but zero order with respect to the aldehyde. The reaction rate is strongly influenced by the substituents of the benzoyl chloride. - Two polar reaction mechanisms which are in accord with these results are outlined and discussed.     

Effects of the substituents on the reactivity of carbonyl oxides. A theoretical study on the reaction of substituted carbonyl oxides with water

The reactions between fifteen carbonyl oxides and water have been investigated with the aim of contributing to a better understanding of the effects of the substituents in the reactivity of carbonyl oxides. We have employed density functional theory and large scale ab initio methods (CCSD(T), CASSCF, and CASPT2), combined with transition state theory, to investigate the addition of water to carbonyl oxide and, for those carbonyl oxides having a methyl substituent in syn, the hydrogen transfer from the methyl group to the terminal oxygen of carbonyl oxide. In this case, the water acts as a catalyst and this reaction can contribute to the atmospheric formation of a hydroxyl radical. Carbonyl oxides with electron withdrawing substituents and zwitterionic character have low energy barriers and react fast, whereas carbonyl oxides with electron releasing substituents have high energy barriers and react slowly. The position of the substituents plays also an important role and carbonyl oxides having a hydrogen atom substituent in syn react faster than carbonyl oxides having a hydrogen atom substituent in anti. The differences in the reactivity of different substituted carbonyl oxides raise up to ten orders of magnitude and the branching ratios for the two different reactions investigated are also reported.     

Chloracylierung und Bromacylierung von Carbonylverbindungen. II. Analyse der Nebenprodukte

Chloroacylation and bromoacylation of carbonyl compounds II. Structure of the by-products The structures of the by-products formed in the reaction between paraformaldehyde and acetyl chloride as well as between acetaldehyde and acetyl chloride are elucidated. Optimum conditions for a high yield of the (α-chloroalkyl) ester 1 were obtained by variation of structure and reaction parameters. A speculative reaction scheme of the formation of by-products is discussed.     

Enhancement of reactivity of the ester carbonyl group by interchromophoric links in photochemical cycloadditions. Intermediacy and roles of plural intramolecular exciplexes

9-Phenanthrenecarboxylic esters as well as naphthalenecarboxylic esters linked with p-methoxystyrene derivatives exert an intramolecular competitive or exclusive oxetane formation through carbonyl addition, although the carbonyl addition is not observed in the corresponding intermolecular systems. The reaction proceeds from the excited singlet state involving plural intramolecular exciplexes. The new aspect of carbonyl addition, i.e., the enhancement of reactivity of the ester carbonyl group by interchromophoric links, is discussed on the basis of photochemical and photophysical observations as well as MO calculations.     

Transformation,par 1′anhydride acètique,d'aldèhydes à caractére èlectrophile prononcè; catalyse par des pyridines. 1. Acyloïnes et hydrates di-o-acètylès d'aldèhydes

2-Benzothiazole-carbaldehyde is transformed into di-O-acetyl-enol-(benzothiazolecarboxyl-2)-oin in the presence of acetic anhydride and of pyridine as catalyst. Without pyridine or with 2,6-lutidine no reaction occurs. A mechanism of this reaction is proposed. No reaction was observed in the case of benzaldehyde. Choral reacts with acetic anhydride in the presence of pyridine as well as of 2,6-lutidine as catalyst to give 1,1-diacetoxy-2,2,2-trichloro-ethane. A mechanism is proposed, in which in an intermediate state the acetate ion (and not pyridine, for steric reasons) attacks the carbon of the carbonyl function of the conjugate acid with the acetylium cation to yield 1,1-diacetoxy-2,2,2-trichloro-ethane. These two reactions occur only with aldehydes whose carbonyl is very electrophilic, and seem to be a possible way to point out the presence of an acylium cation in pyridine medium.     

Copper-catalyzed beta-Boration of alpha,beta-unsaturated carbonyl compounds: rate acceleration by alcohol additives

[reaction: see text] The efficient addition of bis(pinacolato)diboron to alpha,beta-unsaturated carbonyl compounds with a copper-diphosphine catalyst has been carried out. A dramatic rate acceleration of the reaction was realized by adding alcohol additives. With use of this procedure, a variety of alpha,beta-unsaturated carbonyl compounds including conjugated substrates at the acid oxidation level such as esters and nitriles were reacted to give to the corresponding beta-boryl carbonyl compounds in high yields.     

Selective α-bromination of aryl carbonyl compounds: prospects and challenges

The α-bromination of carbonyl compounds is one of the most important transformations and also important precursors in synthetic organic chemistry. Particularly, the side chain monobromination of carbonyl compounds has been a challenging task, because during the reaction a small amount of disubstituted or ring brominated products as an impurity is always accompanied with monosubstituted product in the reaction mixture. In recent years substantial advances have been made for the synthesis of brominated aromatic carbonyl compounds with high selectivity. In this review, we have summarized various methods for the synthesis of α-bromo aromatic carbonyl compounds.     

Stereospecific polymerization of methacrylonitrile. V. Formation of the carbonyl in the polymer

The isotactic polymethacrylonitrile prepared by the organometallic catalysts has carbonyl groups in the polymer. Thus, the carbonyl formation during the polymerization by diethylmagnesium was carefully studied by infrared spectrometry. It was found that the imino anion formed by monomolecular termination of the propagating chain end in the cyclization reaction successively attacks the vicinal pendent nitriles in the polymer so as to form the conjugated cyclic imines, which are hydrolyzed to acid amines during the catalyst decomposition with acidic methanol.     

Cobalt carbonyl catalyzed reaction of tetrahydrofurans with a hydrosilane and carbon monoxide. A new reaction pathway leading to enol silyl ethers.

Cobalt carbonyl catalysed reaction of tetrahydrofurans with HSiEt₂Me and CO (1 atm) took a new reaction pathway leading to enol silyl ethers when acetonitrile was employed as the solvent.     

Diazepines. VI. The chemistry of 3,8-dihalo-11H-dibenzo[c,f] [1,2]diazepin-11-ones

The carbonyl group in the title compounds undergoes a number of reactions typical of ketones but in general is less reactive than a typical ketone. Reaction with hydrazine leads to reduction of the 5,6-bond rather than reaction at the carbonyl group. Reduction of the carbonyl group gives rise to a rather inert carbinol. The carbonyl group appears to exert little influence on typical reactions at the 5,6-position.     

Facile photochemical transformation of alkyl aryl selenides to the corresponding carbonyl compounds by molecular oxygen: use of selenides as masked carbonyl groups

Alkyl aryl selenides with and without functional groups on the alkyl group were transformed efficiently into the corresponding carbonyl compounds, particularly primary alkyl aryl selenides in good yields, by a simple photolysis in the presence of air or oxygen. This transformation can be conducted without protection of functional groups. The yield of carbonyl compounds was much affected by the solvent viscosity, reaction temperature, concentration of dissolved oxygen in the solvents, wavelength of light, and structure of the aryl substituents. The present study indicates that aryl selenides can be considered as a masked carbonyl group that can be easily converted to a carbonyl group by very mild reaction conditions even in the presence of various unprotected functional groups. Therefore, this functional group transformation can be used as an important tool in organic synthesis due to its simplicity and mild reaction condition.     

Recent advances on deoximation: From stoichiometric reaction to catalytic reaction

Recent advances on the deoximation reactions are reviewed in this review. It was shown that catalytic deoximation with molecular oxygen as the mild oxidant should be the developing trend of the reaction.     

Iodine(V) reagents in organic synthesis. Part 4. o-Iodoxybenzoic acid as a chemospecific tool for single electron transfer-based oxidation processes

o-Iodoxybenzoic acid (IBX), a readily available hypervalent iodine(V) reagent, was found to be highly effective in carrying out oxidations adjacent to carbonyl functionalities (to form alpha,beta-unsaturated carbonyl compounds) and at benzylic and related carbon centers (to form conjugated aromatic carbonyl systems). Mechanistic investigations led to the conclusion that these new reactions are initiated by single electron transfer (SET) from the substrate to IBX to form a radical cation which reacts further to give the final products. Fine-tuning of the reaction conditions allowed remarkably selective transformations within multifunctional substrates, elevating the status of this reagent to that of a highly useful and chemoselective oxidant.     

Lewis Acid mediated reactions of zirconacyclopentadienes with aldehydes: one-pot synthetic route to indene and cyclopentadiene derivatives from aldehydes and benzyne or alkynes

One-pot procedures for the preparation of highly substituted indenes, tetrahydroindenes, and cyclopentadienes have been developed by using a combination of zirconocene-mediated Cbond;C-bond-forming reactions with Lewis acid mediated activation of carbonyl groups. The carbonyl groups of aldehydes were deoxygenated in the reaction and behaved formally as a one-carbon unit. A variety of Lewis acids were checked and showed different reactivities in this reaction.     

Reduction of carbonyl compounds via hydrosilylation : I. Hydrosilylation of carbonyl compounds catalyzed by tris(triphenylphosphine)chlororhodium

The hydrosilylation of various carbonyl compounds such as simple aldehydes, simple ketones, α,β-unsaturated carbonyl compounds, α-diketones, acyl cyanides and ketones having an electron-withdrawing group on the α-carbon using tris(triphenylphosphine)chlororhodium as a catalyst is described. Solvolysis of these silyl ethers and silyl enol ethers afforded the corresponding reduced products. The hydrosilylation of α,β-unsaturated carbonyl compounds was found to proceed by 1,4-addition. An oxidative adduct of triethylsilane to the rhodium-(I) complex was obtained as a reaction intermediate. The structure of the adduct was discussed on the basis of its IR and far-IR spectra.     

Synthesis of β-amino carbonyl compounds via a Zn(OTf)2-catalyzed cascade reaction of anilines with aromatic aldehydes and carbonyl compounds

A Zn(OTf)₂-catalyzed cascade reaction of anilines with aromatic aldehydes and carbonyl compounds was described. This one-pot three-component reaction afforded the corresponding β-amino carbonyl compounds, β-amino esters, and β-amino ketones in good to excellent yields. The reaction was also applied for the liquid-phase synthesis of β-amino carbonyl compound library using PEG as a support.     

Catalytic olefination of carbonyl compounds. A new versatile method for the synthesis of alkenes

The review is devoted to a new catalytic olefination reaction (COR) discovered by the authors. This is the reaction between N-unsubstituted hydrazones of carbonyl compounds with dihalides CHal₂XY in the presence of copper(i) chloride to give substituted alkenes. Catalytic olefination is versatile. Variation of the carbonyl and olefinating components opens up the way for the synthesis of various classes of unsaturated compounds including those containing functional groups. The reaction mechanism is discussed and a catalytic cycle describing the process is proposed. A model for estimating and predicting the reactivity of halogen-containing compounds in the COR is developed. The relationship between the structure of the carbonyl substrates and their behavior in the title reaction is elucidated.