Bismuth Triflate–Catalyzed Friedel–Crafts Acylations of Sydnones

Friedel–Crafts acylations of various 3-arylsydnones at the C4 position have been achieved in good yields using 4 equivalents of an alkyl anhydride and 25 mol% each of bismuth triflate and lithium perchlorate in anhydrous acetonitrile at 95 °C. Acylations appear to be faster with arylsydnones bearing electron-donating moieties and sterically unencumbered anhydrides.     

Selective esterifications of alcohols and phenols through carbodiimide couplings

Esterification of carboxylic acids capable of forming ketene intermediates upon treatment with carbodiimides permits the selective acylation of alcohols in the presence of phenols lacking strong electron-withdrawing groups. The selectivity of acylations involving highly acidic phenols could be reversed through the addition of catalytic amount of acid. Esterification of other carboxylic acids was found to proceed through the formation of symmetric anhydrides and provide the opposite chemoselectivity. In both cases the relative acylation rates of substituted phenols are consistent with a reaction mechanism involving an attack of phenolate anions on electrophilic intermediates such as ketenes and symmetric anhydrides, with the carbodiimides serving both as an activating reagent and as a basic catalyst.     

A study of the synthesis and some reactions of perimidines

A study of the preparation of perimidines from 1,8-diaminonaphthalene and carbonyl compounds is presented. The optimum conditions for the reaction of the above diamine with carboxylic acids and esters, acid chlorides, anhydrides and aldehydes are defined. The chemical behavior and a number of previously unreported reactions of perimidines are presented. The latter include N-alkylations, reductions, oxidations and acylations.     

A new odorless one-pot synthesis of thioesters and selenoesters promoted by Rongalite

Rongalite^® promotes cleavage of diaryl disulfides generating chalcogenolate anions that then undergo facile acylation with anhydrides in the presence of CsF to afford thioesters (3) with good to excellent yields. By using the present protocol, 5-arylthio-5-oxopentanoic acid (4) can be facilely prepared. The important features of the methodology are broad substrate scope, simple operation, and no requirement for metal catalysts. It is noteworthy that acylations of diphenyl diselane with anhydrides are also conducted smoothly to afford selenoesters (5) in good yields under the standard conditions.     

Diastereoselective spiroannelation

The diastereoselection in the reaction of 1,4-di-(bromomagnesio) pentane with various structures of lactones and cyclic anhydrides is described.     

Electrophilic substitution of (diamine)tetrahydroxoplatinum(IV) with carboxylic anhydrides. Synthesis and characterization of (diamine)platinum(IV) complexes of mixed carboxylates

A novel series of (diamine)platinum(IV) complexes of mixed carboxylates have been synthesized by electrophilic substitution of the tetrahydroxoplatinum(IV) complex (dach)Pt(OH)4 (dach = trans-(+/-)-1,2-diaminocyclohexane) with three different carboxylic anhydrides, pivalic, acetic, and trifluoroacetic anhydrides. Consecutive two-step acylations with two different carboxylic anhydrides in acetone or dichloromethane gave the mixed carboxylate complexes (dach)Pt(O2CR)x(O2CR')4 - x (R = C(CH3)3 or CF3, R' = CH3, x = 1-4) including all the possible stereoisomers, which could be separated and identified by means of HPLC, column chromatography, 1H NMR, and X-ray crystallography. From analysis of the reaction products we have found that the positions of electrophilic substitution of (dach)Pt(OH)4 were influenced by the kinds of carboxylic anhydrides exhibiting different electrophilicity or steric effects. The initial substitution by the first reactant occurs more favorably on axial OH, but in the case of pivalic anhydride, equatorial substitution is favored probably because of the bulkiness of the pivalate group. Such a result seems to be related to their stereochemical factors rather than to differences in electrophilicity. The lipophilicity of the title complexes was affected not only by the carbon numbers of substituents but also by the conformation of the resulting compound.     

Polymer-supported bases. IX. Synthesis and catalytic activity of polymer-bound 4-(1-pyrrolidino)pyridine moieties

Polystyrene-bound 4-(1-pyrrolidino)pyridine moieties were prepared by the reaction of chloromethylated polystyrene resins with pyrrolidinopyridine derivatives containing hydroxyl groups. The supported amines were effective catalysts for acylations of tert-alcohols or enols, acylrearrangements, and diester synthesis from epoxides and anhydrides. Some of the low ring-substituted (8–15%) catalysts exhibited high activity comparable to that of 4-(N,N-dimethylamino)pyridine, though the activity was a little lower than that of 4-(1-pyrrolidino)pyridine. The recovered catalysts can be re-used, except for acyl rearrangements, without significant decrease in activity.     

Infrared spectroscopy studies of the cyclic anhydride as the intermediate for the ester crosslinking of cotton cellulose by polycarboxylic acids. II. Comparison of different polycarboxylic acids

Polycarboxylic acids have been used as crosslinking agents for cotton cellulose. In our previous research, we used Fourier transform infrared (FT-IR) spectroscopy to investigate the formation of five-membered cyclic anhydride intermediates on cotton fabric by different polycarboxylic acids. In this research, we found that those polycarboxylic acids capable of forming both five- and six-membered cyclic anhydrides form only five-membered cyclic anhydrides. We compared the effectiveness of the polycarboxylic acids with different molecular structures for esterifying cellulose. Those polycarboxylic acids, which have their carboxyl groups bonded to the adjacent carbons of their molecular backbones and are capable of forming five-membered cyclic anhydrides, are more effective for esterifying cellulose than those polycarboxylic acids having their carboxyl groups bonded to the alternative carbons. The only six-membered cyclic anhydride identified is the anhydride formed on the cotton fabric treated with poly(acrylic acid). © 1996 John Wiley & Sons, Inc.     

FT-IR and FT-raman spectroscopy study of the cyclic anhydride intermediates for esterification of cellulose: I. Formation of anhydrides without a catalyst

In recent years, extensive efforts have been made to find nonformaldehyde durable press finishes to replace the traditional formaldehyde-based reagents for producing wrinkle-free cotton fabrics. 1,2,3,4-butanetetracarboxylic acid (BTCA) has been the most effective nonformaldehyde crosslinking agent. Our previous research has indicated that a polycarboxylic acid esterifies cellulose in two steps: the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two adjacent carboxyl groups, and the reaction between cellulose and the anhydride intermediate to form an ester linkage. In this research, we used Fourier transform infrared and Fourier transform Raman spectroscopy to study the formation of cyclic anhydride intermediates by BTCA and other polycarboxylic acids without the presence of a catalyst. We found that BTCA and other polycarboxylic acids in a crystalline state start to form 5-membered cyclic carboxylic anhydrides when the temperature reaches the vicinity of their melting points with the exception of bifunctional acids, which form cyclic anhydrides at temperatures much higher than their melting points. Intermolecular hydrogen bonding between carboxylic acid groups prevents the formation of the cyclic anhydride intermediates at lower temperatures. We also found that polycarboxylic acids in an amorphous state form cyclic anhydrides at much lower temperatures.     

Doubly-charged positive ions following loss of oxygen dianion under conditions of field desorption mass spectrometry

A number of cyclic aromatic anhydrides have been found to exhibit doubly-charged positive ions in their field desorption mass spectrum which correspond to the formal loss of oxygen dianion followed by clustering with a neutral molecule. Admixtures of two anhydrides, which both exhibit this phenomenon, produce heterogeneous doubly-charged cluster ions. Admixture with anhydrides which do not show the effect, produces only homogeneous clusters at reduced intensity.     

Asymmetric catalytic anhydride openings via carbon-based nucleophiles

The asymmetric desymmetrization of cyclic anhydrides via the addition of carbon-based nucleophiles has been the focus of considerable levels of interest because it leads to optically active products. Over the past 20 years, a variety of different catalytic asymmetric alkylation reactions have been developed for the desymmetrization of cyclic anhydrides using different metal reagents as nucleophiles and using chiral ligands. The purpose of this review is to provide an overview of significant developments in this field. ~ 2013 Fen-Er Chen. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

A palladium-catalyzed enantioselective alkylative desymmetrization of meso-succinic anhydrides

Monoalkylation of cyclic anhydrides provides an opportunity to couple a carbon-carbon bond-forming event with the control of backbone stereochemistry. We have developed a palladium-JOSIPHOS catalyst system that desymmetrizes meso-succinic anhydrides using organozinc reagents as nucleophiles, and have found that, in many cases, this reaction proceeds at ambient temperature.     

Investigation of the reaction of some unsaturated dicarboxylic acid anhydrides with cyclic carbonates

This work reports attempts to extend to unsaturated anhydrides the rapid reaction of dicarboxylic acid anhydrides with ethylene carbonate to form polymer directly. The reaction of unsaturated diacid anhydrides with two cyclic carbonates, ethylene and propylene carbonate, leads to gelled products whenever the anhydride is capable of Michael addition, while an anhydride without such unsaturation gave linear polymer in- stead. The GC/MS results, along with efforts to trap radical reactions, support Michael addition as an explanation of gelation in these systems.     

Resonance in aromatic and heteroaromatico-dicarboxylic acids,their anhydrides and imides

It is found thato-dicarboxylic acids derived from pyrrole and 1,2,5-thiadiazole do not form cyclic anhydrides as readily as phthalic acid. This is discussed in terms of ionic resonance structures and derived stabilization of the anhydrides and acids.     

Comparison of the effectiveness of epoxy cure accelerators using a fluorescent molecular probe

A simple optical method for quantitative comparison of the effectiveness of epoxy cure accelerators, used for speeding up the crosslinking process of epoxy resins with cyclic anhydrides, is described. Fluorescent molecular probes and a miniature fiber optic spectrometer have been applied for measurement of the cure kinetics of a model epoxy resin/anhydride composition in the presence of various cure accelerators. A quantitative index of accelerator performance has been determined for several of the most common accelerators.     

Dual Nickel‐ and Photoredox‐Catalyzed Enantioselective Desymmetrization of Cyclic meso‐Anhydrides

The enantioselective desymmetrization of cyclic meso‐anhydrides with benzyl trifluoroborates under nickel‐photoredox catalysis is described. The reaction tolerates a variety of sterically and electronically different trifluoroborates, as well as structurally unique cyclic anhydrides. The trans isomer of the keto‐acid products is also observed at varying levels dependent on the trifluoroborate identity and relative catalyst loading. A mechanism involving decarbonylation and Ni−C bond homolysis of a Ni^II adduct is proposed. This feature allows access to a trans keto‐acid as the major product in high enantioselectivity from a cis meso anhydride.     

The preparation of 7-substituted norbornadiene-2,3-dicarboxylic anhydrides and an experimental and theoretical study of their reactivity

Four new substituted methano-bridged or heteroatom-bridged norbornadienomaleic anhydrides have been prepared and converted to sesquinorbornadiene anhydrides by reaction with cyclic 1,3-dienes. The versatility of parity reversal, in conjunction with N-substituent steric effects, has been used to produce all three possible stereoisomers of the N,O-sesquinorbornadiene anhydrides in separate, stereoselective cycloadditions. The anhydrides have been synthesized by cyclization of their diacids (in situ production) or by flash vacuum pyrolysis of their furan adducts (yielding crystalline products); further fragmentation occurs at these or higher temperatures to produce five-membered carbocyclic or heterocyclic anhydrides. Activation energies have been evaluated for the fragmentation and cycloaddition processes using DFT calculations (B3LYP/6-31G∗) and these calculations correctly predict, which reaction can be intercepted at the norbornadienomaleic anhydride stage and preferred stereochemistry of cycloadducts.     

Highly regioselective lactone formation catalyzed by ruthenium complexes. An application to synthesis of arylnaphthalene lignans

Ruthenium catalyzed hydrogenation of cyclic anhydrides and dehydrogenation of diols have been successfully applied to the highly regioselective synthesis of arylnaphthalene lignans.     

Investigation of the thermal degradation and stability of copolymers of 2-acrylamido-2-methylpropanesulphonic acid and methyl methacrylate

Copolymers of 2-acrylamido-2-methylpropanesulphonic acid (AMPS) and methyl methacrylate (MMA) were prepared. Thermal behaviour was studied by TG and DTG methods. Incorporation of more comonomer units, at various compositions, results in a copolymer more stable than the AMPS homopolymer. Decomposition of the copolymers involves the formation of anhydrides, the majority of which involve six-membered cyclic anhydride rings. Further heating results in the formation of a highly aromatic char at the higher temperatures. The apparent activation energies of decomposition of the homo- and copolymers were established.     

Comparison of microwave-assisted and conventional preparations of cyclic imides

Microwave-assisted preparation of several cyclic imides was performed with four different cyclic anhydrides. All the reactions are significantly faster and the isolated yields are significantly higher compared to conventionally heated reactions. Furthermore, many of these reactions can be performed with a minimal amount of solvent, thereby enabling the synthetic chemist to obtain high quantities of pure cyclic imides in a matter of hours.