Synthesis of 1,4-dioxo-5,8-endomethylene-3,8,9,10-tetrahydrobenz-2,3-oxazine from 3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride

Latvian Institute for Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, 417–418. March, 1995. Original article submitted February 13, 1995.     

Studies in iridoid synthesis. Chemoselective transformations of cis-1,2,4,6-tetrahydrophthalic anhydride

In the course of synthetic studies towards the development of diastereoselective routes to secoiridoid aglycones, cis-1,2,4,6-tetrahydrophthalic anhydride was transformed into the corresponding lactone cis-3a,4,7,7a-tetrahydro-3H-isobenzofuran-1-one, which served as a key precursor for a variety of chemoselective synthetic manipulations. Unsuccessful formylation of an ester intermediate resulted in a (E/Z) mixture of vinyl alcohols which were protected as acetates and as a single p-methoxybenzyl (PMB) ether (E) isomer. Dihydroxylation of the cyclohexene motif using OsO(4) led to the unexpected deprotection of the PMB ether. On the other hand, successful formylation of a suitably silyl protected lactonised intermediate was achieved using tert-butoxybis(dimethylamino)methane, or Bredereck's reagent. Tetrabutylammonium fluoride (TBAF) deprotection of a methoxyethoxymethyl (MEM)-ether intermediate serendipitously afforded an approximately 1 : 1 mixture of pyrano-pyranones, which are products of a seldom encountered intramolecular Michael addition, using an oxygen donor, to the terminus of an alpha,beta-unsaturated system, followed by beta-elimination of the MEM moiety.     

Free-radical-induced polymerization of epoxides in the presence of maleic anhydride

The free-radical-induced reactions of cyclohexene oxide in the presence of maleic anhydride have been found to lead to polyether in presence of AIBN and to a mixture of polyether, ester, and maleic anhydride adduct of polyether with di-tert-butyl peroxide (DTBP), the amounts of the mixture components depending on the concentration of DTBP and the temperature. Analogous reactions in the presence of succinic anhydride lead to no polyether. The obtained polyether has no hydroxyl group. The reaction appears to consist of three different steps, radical initiation, cationic propagation, and radical termination.     

Laser-initiated polymerization of epoxies in the presence of maleic anhydride

Laser-initiated polymerization of cyclohexene oxide in the presence of maleic anhydride was investigated. The influences of solvents laser irradiation time and the monomer feed ratio on the polymer yield and composition were evaluated. The rate of polymerization increased with an increase in the molar concentration of maleic anhydride in the monomer feed. Short irradiation times of 1–3 min duration gave very high yield of epoxy polymer (>80% conversion). Infrared spectral studies of the polymer product indicated the formation of polyether linkage at lower levels of conversion and an adduct of polyether and maleic anhydride at higher polymer conversions. The quantitative chemical analyses results also showed similar results. The results indicated that the polymerization was initiated by the excited charge transfer complex between the electron donor, cyclohexane oxide, and the electron acceptor–maleic anhydride. In the initial stages of polymerization, cyclohexene oxide undergoes a cationic polymerization in the presence of the radical anion of maleic anhydride. Laser-initiated polymerization of cyclohexene oxide/maleic anhydride is several hundred times more efficient than UV-initiated polymerization, as measured by the energy absorbed by the polymer system.     

Structure of poly(maleic anhydride)

The bulk polymerization of maleic anhydride initiated with acylperoxides, di-tert-butyl peroxide, AIBN, or pyridine proceeds with evolution of CO₂. The amount of CO₂ generated depends on the nature and the concentration of the initiator. With peroxide initiators, less than 5% of the polymerized maleic anhydride is decarboxylated. ¹H-NMR spectra, obtained on the benzoyl peroxide-initiated polymer and its methyl ester, are consistent with the unrearranged poly(maleic anhydride) structure and rule out the polycyclopentanone structure proposed by Braun and co-workers. Base-initiated polymaleic anhydride is substantially decarboxylated, and the resulting polymer has anhydride and carboxyl groups. Elemental analyses and ¹H-NMR spectra obtained on the pyridine-initiated polymer and its methyl ester refute both the cis-poly(vinylene ketoanhydride) structure suggested by Schopov and the polycylopentanone structure proposed by Braun and co-workers.     

Photometric determination of maleic anhydride in maleinized adducts

A procedure is developed for the determination of maleic anhydride in maleinized adducts based on natural oils by the reaction yielding molecular complexes of 2-methylimidazole and maleic anhydride in dimethyl sulfoxide. The procedure can be used for the determination of maleic anhydride in polymers based on a mixture of anhydrides in the presence of acid.     

Radical-catalyzed homopolymerization of maleic anhydride in presence of polar organic compounds

Polar organic compounds either (1) inhibit the peroxide-catalyzed bulk homopolymerizations of both MAH and MMA at 80°C, (2) do not inhibit the polymerization of either MAH or MMA, or (3) inhibit the polymerization of MAH but not that of MMA. Compounds generally used as polymerization inhibitors or antioxidants inhibit the polymerizations of both MAH and MMA, presumably by interaction with peroxide decomposition products. Ketones, ethers, acids, esters, nitriles, imides, sulfones, sulfonates, sulfonamides, and acyl disulfides do not inhibit either MAH or MMA polymerization. However, amides, lactams, carbamates, amine oxides, phosphites, phosphates, phosphonates, phosphoramides, phosphine oxides, monosulfides, sulfoxides, aryl disulfides, and thiazyl disulfides inhibit the polymerization of MAH but not that of MMA. Inhibition presumably occurs as a result of electron transfer from the nitrogen-, phosphorous- or sulfur-containing electron donor compound to the MAH carbocation which is an intermediate in the polymerization of MAH.     

Potentiometric determination of urea with perchloric acid in acetic anhydride

A potentiometric method for the quantitative determination of urea is proposed. Urea is titrated with perchloric acid in acetic anhydride solvent. This method is rapid and less costly than the semi-micro Kjeldahl method. In addition, its accuracy is nearly identical with that of Kjeldahl's method. An analysis of a given sample is completed in about 30 min.     

Grafting in reaction of polyethylene and poly(maleic anhydride)

Polyethylene has been grafted in a reaction with poly(maleic anhydride) in the presence of radical initiators. The role of oxygen, the comparison of the effectiveness of benzoyl peroxide and AIBN, and the kinetics of the reaction suggest that side chains are formed via a combination of the macroradicals of both polymers.     

The vibrational spectrum of (maleic anhydride)iron tetracarbonyl

On the basis of solid-phase IR and Raman spectra, with some solution data for the IR, a reasonably complete vibrational assignment has been made for the modes of maleic anhydride in (maleic anhydride)iron tetracarbonyl. Shifts in v(C=C) and δ(CH) are consistent with a strong interaction with the metal, but relatively little coupling between the modes. More restricted assignments were made for modes associated with the (maleic anhydride)iron and Fe(CO)₄ fragments.     

Thermal behavior of the maleic anhydride modified poly(3-hydroxybutyrate)

Poly(3-hydroxybutyrate), PHB has been structurally modified through reaction with maleic anhydride, MA. Transesterification reaction was carried out fixing the PHB and MA and besides time and temperature the concentration of the triethylamine (used as catalyst) was changed. Glass transition, melting and crystallization temperature obtained from DSC curves and thermal degradation temperatures obtained from TG traces were used to evaluate the influence of the reaction conditions on the modification of PHB according to factorial design. On the base of the results the optimum conditions are to perform the PHB modification reaction with MA reaction at 110°C for 1 h with 5% v/v triethylamine.     

Synthesis of macrocyclic compounds with steric barriers in macroheterocycle proceeding from (Z)-1,2,3,6-tetrahydrophthalic and phthalic acids

Using 1,2-dibromoethane, (E)-1,4-dibromo-2-butene, (Z)-1,2,3,6-tetrahydrophthalic and phthalic acids we obtained along [1+1] scheme uncommon macrocyclic compounds containing ester groups, multiple bonds, and amide moieties in the macroheterocycle. The neutralization of bis-acids with ethylenediamine gave the corresponding macrocyclic diammonium salts that on heating to the melting point were converted into the corresponding macrocyclic diamides. The structure of compounds obtained was established from the elemental analyses, IR and NMR spectra.     

2-methylimidazole as a reagent for the photometric determination of maleic anhydride

The formation of molecular complexes of maleic anhydride with some substituted imidazoles in acetonitrile, dimethylformamide, and dimethyl sulfoxide was studied. The selection of 2-methylimidazole as a reagent for the photometric determination of maleic anhydride in the dimethyl sulfoxide medium was substantiated using kinetic and spectrometric techniques.     

Peroxide-catalyzed grafting of maleic anhydride onto molten polyethylene in the presence of polar organic compounds

The crosslinking of LDPE resulting from reaction with dicumyl peroxide at 180°C is increased in the presence of maleic anhydride (MAH). The presence of electron-donating nitrogen-containing compounds (amides, lactams, disubstituted aromatic amines, and amine oxides), phosphorous-containing compounds (phosphites, phosphates, phosphonates, phosphoramides, and phosphine oxides) and sulfur-containing compounds (sulfoxides, aryl disulfides, and thiazyl disulfides) which inhibit the homopolymerization of MAH but not that of methyl methacrylate, prevents crosslinking and yields soluble PE containing MAH units. Crosslinking, due to coupling of PE^˙ macroradicals formed by hydrogen abstraction from PE by excited MAH, is prevented by electron donation from the additive to the MAH⁺ cation which is present in the MAH+?MAH excimer as well as in the excimer which is appended to the PE.     

Effect of the initial maleic anhydride content on the grafting of maleic anhydride onto isotactic polypropylene

A series of ¹³C‐enriched maleic anhydride grafted isotactic polypropylene samples were prepared in solution at 170 °C by changes in the initial maleic anhydride content. The NMR spectra of the samples showed that the signals of the maleic anhydride attached to the tertiary carbons of the isotactic polypropylene chains increased considerably with increasing maleic anhydride content, whereas the signals of the maleic anhydride on the radical chain ends (with a single bond) arising from β scission did not. On the other hand, the signals of the maleic anhydride on the radical chain ends with double bonds increased markedly with increasing maleic anhydride content, and this suggested that β scission could occur extensively after maleic anhydride was attached to the tertiary carbons. As a result, the molecular weight of the grafted polypropylene decreased significantly with increasing maleic anhydride content in this study. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5529–5534, 2005     

Bisacylation of the anhydride and esters of 4-methyl-1,2,3,4-tetrahydrophthalic acid

The bisacylation of the anhydride and esters of 4-methyl-1,2,3,4-tetrahydrophthalic acid by anhydrides of carboxylic acids in the presence of perchloric acid results in the formation of derivatives of 1,3-dialkyl-6, 7-dicarboxy-5,6,7,8-tetrahydro-2-benzopyrylium salts. Some reactions of the salts obtained, including their recyclization under the action of nucleophiles, have been studied. A convenient preparative method for the synthesis of 6,7-dicarboalkoxy-5,6,7,8-tetrahydroixoquinolines has been developed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1318–1321, October, 1984.     

Fumarate,maleate and maleic anhydride complexes of platinum(O)

Dimethyl fumarate (dmf), diethyl fumarate (def), dimethyl maleate (dmm), and maleic anhydride (ma) react with [Pt(cod)₂] (cod = cyclo-octa-1,5-diene) and with [Pt(C₂H₄)₃] to give ‘mixed’ olefin platinum(O) complexes, e.g., [Pt(cod)(def)], [Pt(cod)(ma)], [Pt(C₂H₄)(dmf)₂] or [Pt(C₂H₄)(dmm)₂]. Tris-(olefin)platinum complexes [Pt(def)₃] and [Pt(dmf)₃] have also been obtained.