Heterocyclic epoxy compounds

Heterocyclic Epoxy Compounds. The technically most important heterocyclic epoxy resin is triglycidyl isocyanurate, obtained by reacting cyanuric acid with epichlorohydrin (Araldite PT 810, Ciba-Geigy Tepic, Nissan). This trifunctional epoxy resin is combined with carboxy-terminated polyesters to give weather-resistant powder coatings [2.122]-[2.124]. 

Cycloaliphatic and heterocyclic epoxy have better weather resistance and less tendency to yellow and chalk than do aromatic epoxy resins. These resins possess excellent electrical properties and are often used in electrical and electronic applications. They are generally formulated into casting and filament winding compounds. 

Ohler, E., El-Badawi, M., and Zbiral, E., Dialkyl (l,2-epoxy-3-oxoalkyl)phosphonates as synthons for heterocyclic carbonyl compounds. Synthesis of acyl-substituted thiazoles, indolizines, imidazo[ 1,2-fii]pyridines and imidazo[l,2-fii]pyrimidines, Chem. Ber., 118, 4099, 1985. 

There are several reactions (bromination, oxymercuration, epoxidation) of olefinic hydroxy and epoxy compounds in which the oxygen function can react intramolec-ularly with an intermediate formed at the double bond, leading to an oxygen-containing heterocyclic compound (tetrahydrofuran or tetrahydropyran) (Scheme 6). 

As the reaction proceeds a band appears in the 300-310 nm region. However, the use of a heterocyclic amine with epoxy compounds does not always result in such changes in the UV spectrum. For instance, with 2,6-dimethylpyridine the consumption of aromatic molecules on interaction with PhGE is not observed. The reaction of 2,6-dimethylpyridine with PhGE is characterized by the appearance and accumulation of substances producing two bands in the visible spectrum (at 408 and 505 nm), and by a decrease in the nmnber of epoxide groups. 

Cyclic ethers of the epoxide type can be named additively as... oxides,sub-stitutively as epoxy... compounds (compare with bridged systems, p. 65) or, most uniformly, as heterocycles. 

Heterocycles Both non-aromatic unsaturated heterocycles and heteroaromatic compounds are able to play the role of ethene dipolarophiles in reactions with nitrile oxides. 1,3-Dipolar cycloadditions of various unsaturated oxygen heterocycles are well documented. Thus, 2-furonitrile oxide and its 5-substituted derivatives give isoxazoline adducts, for example, 90, with 2,3- and 2,5-dihydro-furan, 2,3-dihydropyran, l,3-dioxep-5-ene, its 2-methyl- and 2-phenyl-substituted derivatives, 5,6-bis(methoxycarbonyl)-7-oxabicyclo[2.2.1]hept-2-ene, and 1,4-epoxy-l,4-dihydronaphthalene. Regio- and endo-exo stereoselectivities have also been determined (259). 

Polyamino acids are easy to prepare by nucleophUe-initiated polymerisation of amino acid JV-carboxyanhydrides. Polymers such as poly-(L)-leucine act as robust catalysts for the epoxi-dation of a wide range of electron-poor alkenes, such as y-substituted a,Ji-unsaturated ketones. The optically active epoxides so formed may be transformed into heterocyclic compounds, polyhydroxylated materials and biologically active compounds such as dUtiazem and taxol side chain. 

Relatively few simple pyrimidine monomers have been incorporated into heterocyclic polymers (70MI11100). By far the greatest efforts with this ring system have involved polymerizable derivatives of nucleic acid bases and related compounds (81MH1102). The majority of this work has involved the synthesis and free radical polymerization of suitable vinyl- and acrylic-functional monomers, e.g. (134)-(136), although epoxy and other derivatives have also been studied. A number of the polymers exhibit base-paired complex formation with natural nucleic acid polymers or synthetic analogues, have found use in... 

The catalytic effect has been explained in terms of the activation of the anhydride by interaction with the amine to give a zwitterionic intermediate (47 Scheme 10) (B-68MI11501). Imidazoles have also been suggested as accelerators for anhydride cures (68USP3394105). A review of the patent literature (B-77MI11502) shows that several heterocyclic compounds are of interest as curatives for epoxy resins. 

Specialty Epoxy Resins. In addition to bisphenol, other polyols such as aliphatic glycols and novolaks are used to produce specialty resins. Epoxy resins may also include compounds based on aliphatic, cycloaliphatic, aromatic, and heterocyclic backbones. Glycidylation of active hydrogen-containing structures with epichlorohydrin and epoxidation of olefins with peracetic acid remain the important commercial procedures for introducing the oxirane group into various precursors of epoxy resins. 

End-functionalized polymers with polymerizable groups such as double bonds and heterocycles of course provide macromonomers allyl, vinyl ester, vinyl ether, lactone, and epoxy are examples of such a category whose a-ends are not susceptible or have little susceptibility to metal-catalyzed radical polymerization. As discussed above, for example, allyl chloride and bromide (FI-33 and FI-34) are effective initiators to be used for styrene with CuCl and CuBr catalysts,161 while allyl compounds with remote halogens such as FI-35 and FI-36 allow the polymerization of methacrylates with high initiation effi-... 

Azanaphthalene iV-oxides undergo photochemical deoxygenation reactions in benzene containing BF3 OEt2, resulting in amines in 70-80% yield these amines are important in the synthesis of heterocyclic compounds. Azidotrimethylsilane reacts with traws-1,2-epoxy alky Isilanes in the presence of BF3-OEt2 to produce (Z)-l-alkenyl azides. The cis-1,2-epoxyalkylsilanes undergo rapid polymerization in the presence of Lewis acids. 

---