Rhodium-catalyzed allyl transfer from homoallyl alcohols to acrylate esters via retro-allylation

Retro-allylation of homoallyl alcohols by rhodium catalysts occurs to generate allylrhodium species. Insertion of acrylate esters to the allylrhodiums proceeds to give the corresponding 2,5-hexadienoate esters in situ. Subsequent isomerization or iterative 1,4-addition takes place in the same pots to furnish the corresponding 2,4-hexadienoate esters or triesters in good yields.     

Studies on the polymerization of ethyl acrylate. II. Chain transfer studies

Transfer constants for different solvents representing hydrocarbons, halogenated compounds, alcohols, ketones, acids, and esters were determined in the thermal polymerization of ethyl acrylate at 80°C and they are compared with the available data on methyl acrylate and ethyl methacrylate. It was observed from the values of transfer constants that ethyl acrylate radicals are a little more effective than methyl acrylate or ethyl methacrylate in abstracting hydrogen atom from hydrocarbons and alcohols. In acetic and n-butyric acid media, it has been found, by the aid of endgroup analysis, that the derived solvent radicals from transfer reactions are not too efficient to start a new chain.     

A new route to acrylate oils: Crosslinking and properties of acrylate triglycerides from high oleic sunflower oil

Triglycerides with acrylate functionality were prepared from a new route that involves the singlet oxygen photooxygenation of high oleic sunflower oil and further reduction of the resulting hydroperoxide derivatives to a mixture of secondary allylic alcohols. These unsaturated alcohols can be further reduced to saturated alcohols. These two new hydroxyl‐containing triglycerides were functionalized as acrylate esters and radically crosslinked in presence of different amounts of pentaerythritol tetraacrylate. The crosslinking reactions were followed by FTIR spectroscopy and the thermal properties of the final materials were evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1159–1167, 2009     

A practical new chiral controller for asymmetric Diels-Alder and alkylation reactions

[formula: see text] The enantiomerically pure hydroxy sulfones (+)- and (-)-2 have been prepared from 1,2-epoxycyclohexane by a simple and practical procedure. The acrylate esters of these alcohols undergo BCl3-catalyzed Diels-Alder reactions with a variety of dienes at -78 to -55 degrees C in CH2Cl2 or C7H8 with high dienophile face selectivity (Table 1). The chiral esters so formed are readily cleaved with recovery of the controllers (+)- or (-)-2. Esters of (+)- and (-)-2 can be converted to Z-potassium enolates and alkylated with high face selectivity.     

Synthesis of pentafluorophenyl(meth)acrylate polymers: New precursor polymers for the synthesis of multifunctional materials

Pentafluorophenyl acrylate and -methacrylate were polymerized using AIBN as a thermal initiator. The obtained polymers were soluble polymeric active esters that could be used for the preparation of multifunctional polymers. The reactivity of poly(pentafluorophenylacrylate) and poly(pentafluorophenylmethacrylate) towards primary and secondary amines, as well as alcohols was investigated in a quantitative way. Both poly(active esters) reacted satisfactorily with aliphatic primary and secondary amines but only low conversion was found in the case of aromatic amines. Conversions of only 30% were reached when poly(pentafluorophenylacrylate) was treated with one equivalent of alcohol under base catalysis. In time resolved FT-IR studies the rate constants of the polymer analogous reactions were determined.     

Epoxide as precatalyst for metal-free catalytic transesterification

Transesterification of methyl esters was accelerated by an in situ-generated metal-free catalyst comprising a quaternary alkylammonium salt and an epoxide. The combination of a quaternary alkylammonium acetate and glycidol is optimal, and various esters were synthesized from methyl esters with alcohols in good to excellent yield. Analysis of the catalyst solution revealed that basic species are generated by the ring-opening reaction of epoxide.     

环己酮与丙烯酸甲酯及(S)-3-(2′-氧环己基)-丙酸与醇的酯化反应

在(R)TTCA·K催化下由环己酮直接与丙烯酸甲酯进行Michael加成反应得到了(S)-3-(2′-氧环己基)-丙酸甲酯, [α]20D-4.14(41.5% e.e.).     

Facile synthesis of alpha-substituted acrylate esters

Treatment of 5-monosubstituted Meldrum's acids with dimethylmethyleneimmonium iodide (Eschenmoser's iodide salt) in methanol gives alpha-substituted acrylate methyl esters in good yields. Easy access to 5-monosubstituted Meldrum's acids allowed us to synthesize a wide variety of alpha-substituted acrylate methyl esters. The reaction conditions are mild and tolerate many functional groups commonly used in organic synthesis; thus, this new method has potential as an alternative to conventional preparative methods for alpha-substituted acrylate esters.     

Efficient transesterification/acylation reactions mediated by N-heterocyclic carbene catalysts

Imidazol-2-ylidenes, a family of N-heterocyclic carbenes (NHC), are efficient catalysts in the transesterification involving numerous esters and alcohols. Low catalyst loadings of aryl- or alkyl-substituted NHC catalysts mediate the acylation of alcohols with enol acetates in short reaction times at room temperature. Commercially available and more difficult to cleave methyl esters react with primary alcohols in the presence of alkyl-substituted NHC to efficiently form the corresponding esters. While primary alcohols are selectively acylated over secondary alcohols with use of enol esters as acylating agents, methyl and ethyl esters can be employed as protective agents for secondary alcohols in the presence of the more active alkyl-substituted NHC catalysts. The NHC-catalyzed transesterification protocol was simplified by generating the imidazol-2-ylidene catalysts in situ.     

Rapid procedure for the isolation and analysis of fatty acid and fatty alcohol fractions from wax esters of marine zooplankton

A rapid and simple method for the isolation of fatty acid methyl esters and fatty alcohols from the lipid fraction of marine zooplankton is described. Wax esters are the dominant lipid class in most calanoid copepods and trans-esterification results in a high fatty alcohol content in the analytical extract. Current procedures for the separation and purification of lipid classes by preparative thin-layer chromatography are time-consuming and are subject to low recovery of the analytes. In this method, fatty acid methyl esters and fatty alcohols were separated by liquid chromatography using silica or honded amino-silica as the stationary phase. The procedure is equally applicable to the analysis of zooplankton with low wax ester (and hence fatty alcohol) content, for example, a number of species of euphausiid and, generally, for samples of low mass.     

Alpha-phosphono lactone analogues of cytidine and cytosine arabinoside diphosphates: synthesis via ring closing metathesis

alpha-Phosphono lactone derivatives of the nucleosides cytidine and cytosine arabinoside have been prepared from the corresponding nucleoside aldehydes. The stereochemical outcome of allylation reactions with these aldehydes was found to be dependent upon both the choice of protecting groups for the 2'- and 3'-hydroxyl groups and, to some extent, the nature of the Lewis acid catalyst employed. Ultimately, conditions were found that favored either the 5'R or 5'S diastereomer from different cytidine aldehydes, and gave some stereoselectivity in additions to an aldehyde derivative of ara-C. The resulting homoallylic alcohols were used as substrates in attempted Knovenagel and Horner-Wadsworth-Emmons condensations, but elimination was found to predominate over lactone formation under the conditions employed. The desired alpha-phosphono lactones could be prepared through a reaction sequence that included ring-closing metathesis on acrylate esters of the homoallylic alcohols, followed by reduction of the resulting alpha,beta-unsaturated lactones and carbon-phosphorus bond formation on enolates generated from the saturated lactones.     

Ionic Pathways in the Photochemistry of Cyclic Sulfite Esters

The photochemistry of cyclic carbonate esters proceeds by the photochemical extrusion of carbon dioxide to give 1, 3‐diradicals which produce oxiranes as well as other radical derived species. The corresponding cyclic sulfite esters, upon irradiation, give intermediates that are trapped by alcohols yet generate no oxiranes. These results are consistent with ionic intermediates.     

Compositional analysis of UV-cured acrylic ester resins by pyrolysis–gas chromatography in the presence of organic alkali

Compositional analysis of UV-cured resins consisting of multi-component acrylic esters was studied by pyrolysis–gas chromatography (Py–GC) in the presence of organic alkali, tetramethylammonium hydroxide (TMAH). The pyrograms of the UV-cured resins formed from ethylene oxide modified bisphenol A diacrylate (EBADA) contained specific products such as methyl acrylate (MA) and various dimethyl ethers of ethylene oxide modified bisphenol A reflecting the numbers of ethylene oxide units in the original EBADA. Meanwhile the pyrograms of the UV-cured resins comprised of acrylated polyfunctional aliphatic alcohols such as pentaerythritol triacrylate (PETA) and dipentaerythritol hexacrylate (DPEHA) contained methyl ethers reflecting the structure of the original alcohols. In addition, considerable amounts of pyrolyzates with non-methylated hydroxyl groups were also detected for aliphatic alcohol moieties. The compositions of the UV-cured resins containing multi-component acrylic esters were also analyzed based on the relative yields of the characteristic pyrolyzates of each acrylic ester. For calibration purpose, a series of UV-cured standard samples, which contained known amounts of the individual acrylic ester and neopentylglycol diacrylate (NPGDA) used as an internal standard, were measured. The compositions of the multi-component UV-cured resins determined using this approach showed good agreement with the theoretical values estimated from the feed composition.     

Introducing efficient palladium catalyzed cross coupling reaction of tertiary alcohols and aroyl chlorides for the synthesis of highly substituted esters

Esters are chemical compounds with many practical uses. The common type of esterification is called the Fischer esterification. Another one is by the action of acid chlorides on alcohols but not with tertiary alcohols. The stable carbenium ions formed from tertiary alcohols favor elimination and the byproduct, hydrogen chloride prevents ester formation. In this new report, palladium inserted ArCOPdCl species reacts with tertiary alcohols and cross-coupling under microwave heating, minimizes the formation of probable carbenium ion, and promotes successful production of highly substituted esters in good to high yields.     

Reaction of diazonium salts with transition metals—III: Palladium(0)-catalyzed arylation of unsaturated compounds with arenediazoium salts

Palladium (0) catalyzed reactions of arenediazonium salts for arylation of aliphatic and cyclic olefins and allylic alcohols, styrene and ethyl acrylate were studied. Effects of the olefinic compounds and other reaction variables on the arylation were presented. Arylpalladium species was proposed as the most plausible intermediated in this reaction.     

Radical additions to 1,2-dichlorodifluoroethene

Fluorine containing alcohols, esters and ethers have been obtained by peroxide induced radical addition of alcohols, esters and ethers to 1,2-dichlorodifluoroethene.The influence of the kind and amount of the peroxide has been studied and the reactivity of alcohols, esters and ethers compared.     

Catalytic enantioselective intermolecular reductive aldol reaction to ketones

We describe the first example of a catalytic enantioselective intermolecular reductive aldol reaction. Three types of reactions were studied: (1) reactions between acetophenone and methyl acrylate; (2) reactions between symmetric ketones and β-substituted α,β-unsaturated esters; and (3) reactions between acetophenone derivatives and an allenic ester. Although only moderate enantioselectivity was obtained in the first reaction type, high to excellent enantioselectivity was realized in the enantio-induction at the α-position in the second reaction type and at the δ-position in the third reaction type. Specifically, the third reaction type afforded the corresponding tertiary alcohols with up to 99% ee. Pre-activation of the nucleophile by silyl enolate formation is not necessary in these one-pot catalytic enantioselective reductive aldol reactions.     

On the synthesis of pure (meth) acrylate esters and their corresponding homopolymers

We have observed that homopolymers of certain (meth)acrylate esters, prepared by the Schotten–Baumann method of (meth)acryloyl chloride and desired alcohol, in the presence of triethylamine or pyridine, formed gels. The mechanism of gelation was investigated and found to be due to a diene impurity, (meth)acrylic anhydride, which cannot be easily separated from many (meth)acrylate esters. For preparation of pure (meth)acrylate esters, the S_N2 displacement reaction of (meth)acrylate anion with the desired chloro compound is recommended. The yields of the two reactions are comparable, and even t-butoxycarbonylmethyl methacrylate is produced in 73% yield by the recommended method.     

Ultrafast SET‐LRP of methyl acrylate at 25 °C in alcohols

Alcohols are known to promote the disproportionation of Cu(I)X species into nascent Cu(0) and Cu(II)X. Therefore, alcohols are expected to be excellent solvents that facilitate the single‐electron transfer mediated living radical polymerization (SET‐LRP) mediated by nascent Cu(0) species. This publication demonstrates the ultrafast SET‐LRP of methyl acrylate initiated with bis(2‐bromopropionyloxy)ethane and catalyzed by Cu(0)/Me₆‐TREN in methanol, ethanol, 1‐propanol, and tert‐butanol and in their mixture with water at 25 °C. The structural analysis of the resulting polymers by a combination of ¹H NMR and MALDI‐TOF MS demonstrates the synthesis of perfectly bifunctional α,ω‐dibromo poly(methyl acrylate)s by SET‐LRP in alcohols. Moreover, this work provides an expansion of the list of solvents available for SET‐LRP. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2745–2754, 2008     

Some approaches to the synthesis of fluorine-containing alcohols and esters

Among F-containing alcohols only trifluoroethanol, the so-called ‘telomer alcohols’ [H(CF₂CF₂)_nCH₂OH], and certain esters of 2-(F-alkyl)ethanols and 3-(F-alkyl)propanols, have achieved commercial importance. Their utilization has been limited by lack of suitable methods of synthesis and by their high cost. Yet F-containing alcohols and their esters have unique properties, and comprise a versatile class of compounds. It is to be noted that completely fluorinated esters have recently become available.F-substituted alcohols must be made by special, less well-known methods. Routes based on tetrafluoroethylene (TFE) as starting material are of current interest. F-alkyl iodides (R_FI) are made in two steps from TFE. Reaction of R_FI with ethylene gives 2-(F-alkyl)-1-ethanes, and under suitable conditions, higher telomers in high yield. Displacement of iodine of R_FCH₂CH₂I by an acyloxy group gives an ester, such as acrylate or fumarate of the F-substituted alcohol. Several methods have been discovered for this process, most recently by reaction with N-methylformamide or N,N-dimethylformamide and water. Free radical addition of R_FI to vinyl acetate and subsequent reduction provided 2-(F-alkyl)ethanols in excellent yield. Similar steps using allyl acetate gave both 3-(F-alkyl)-1-propanols and 3-(F-alkyl)-2-propanols; the latter compound also was formed by hydrolysis of the initial adduct. These various methods will be outlined and some recent results in a study of O-alkylation will be presented.Support by the Central Research Group, Ciba-Geigy Corp., Ardsley, N.Y. is gratefully acknowledged.