Isocyanates unsaturated

PVC epoxy, polyester-isocyanate, unsaturated polyester, vinyl chloride-acetate copolymer, polyvinyl acetate, polyvinyl alkyl ether, ethylene-vinyl acetate, nitrile rubber-phenolic, neoprene rubber, polyisobutylene rubber, polyurethane rubber, and polysulfide rubber. See discussion in Section 6.3.28 concerning migration of plasticizers in PVC. 

Pd-cataly2ed reactions of butadiene are different from those catalyzed by other transition metal complexes. Unlike Ni(0) catalysts, neither the well known cyclodimerization nor cyclotrimerization to form COD or CDT[1,2] takes place with Pd(0) catalysts. Pd(0) complexes catalyze two important reactions of conjugated dienes[3,4]. The first type is linear dimerization. The most characteristic and useful reaction of butadiene catalyzed by Pd(0) is dimerization with incorporation of nucleophiles. The bis-rr-allylpalladium complex 3 is believed to be an intermediate of 1,3,7-octatriene (7j and telomers 5 and 6[5,6]. The complex 3 is the resonance form of 2,5-divinylpalladacyclopentane (1) and pallada-3,7-cyclononadiene (2) formed by the oxidative cyclization of butadiene. The second reaction characteristic of Pd is the co-cyclization of butadiene with C = 0 bonds of aldehydes[7-9] and CO jlO] and C = N bonds of Schiff bases[ll] and isocyanate[12] to form the six-membered heterocyclic compounds 9 with two vinyl groups. The cyclization is explained by the insertion of these unsaturated bonds into the complex 1 to generate 8 and its reductive elimination to give 9. 

Gycloaddition Reactions. Isocyanates undergo cyclo additions across the carbon—nitrogen double bond with a variety of unsaturated substrates. Addition across the C=0 bond is less common. The propensity of isocyanates to undergo cycli2ation reactions has been widely explored for the synthesis of heterocycHc systems. Substrates with C=0, C=N, C=S, and C=C bonds have been found to yield either 2 + 2, 2 + 2 + 2, or 2 + 4 cycloadducts or a variety of secondary reaction products (2). 

Because of their relative instabiUty, primary phosphine oxides caimot be isolated and must be converted direcdy to derivatives. Primary and secondary phosphine oxides undergo reactions characteristic of the presence of P—H bonds, eg, the base-cataly2ed nucleophilic addition to unsaturated compounds such as olefins, ketones, and isocyanates (95). 

Polymers. The molecular weights of polymers used in high energy electron radiation-curable coating systems are ca 1,000—25,000 and the polymers usually contain acryUc, methacrylic, or fumaric vinyl unsaturation along or attached to the polymer backbone (4,48). Aromatic or aUphatic diisocyanates react with glycols or alcohol-terrninated polyether or polyester to form either isocyanate or hydroxyl functional polyurethane intermediates. The isocyanate functional polyurethane intermediates react with hydroxyl functional polyurethane and with acryUc or methacrylic acids to form reactive p olyurethanes. 

The Curtius rearrangement is a useful method for the preparation of isocyanates as well as of products derived thereof. The substituent R can be alkyl, cycloalkyl, aryl, a heterocyclic or unsaturated group most functional groups do not interfere. 

In yet another example of an in situ reductive generation of an enolate, fi-amido esters are formed via the reaction of an o, /3-unsaturated ester with a silane in the presence of an isocyanate (Eq. 294).475 The yields obtained using methyl acrylate and methyl crotonate as substrates are generally excellent. 

Several approaches to the 1,2,3-triazole core have been published in 2000. Iodobenzene diacetate-mediated oxidation of hydrazones 152 led to fused 1,2,3-triazoloheterocycles 153 <00SC417>. Treatment of oxazolone 154 with iso-pentyl nitrite in the presence of acetic acid gave 1,2,3-triazole 155, a precursor to 3-(W-l,2,3-triazolyl)-substituted a,P-unsaturated a amino acid derivatives <00SC2863>. Aroyl-substituted ketene aminals 156 reacted with aryl azides to provide polysubstituted 1,23-triazoles 157 <00HC387>. 2-Aryl-2T/,4/f-imidazo[43-d][l,2,3]triazoles 159 were prepared from the reaction of triethyl AM-ethyl-2-methyl-4-nitro-l//-imidazol-5-yl phosphoramidate (158) with aryl isocyanates <00TL9889>. 

Treatment of y-nitrothioamides 368 with phenyl isocyanate and triethylamine (nitrile oxide generation conditions) leads to a.j3-unsaturated nitriles 369. The mechanism proposed for this reaction is shown in Scheme 1.42, which includes the dehydration stage of the nitrile oxide formed (418). 

Epoxies - The term "reactive oligomer" is relatively new but the concept is fairly old. This concept has been used for many years with systems such as epoxies, phenolics, unsaturated esters, cyanates, isocyanates and many other crosslinked systems. An example of a 177°C curing epo y system (Narmco s 5208) which was introduced into the marketplace about 1971 is shown in Eq. 1. 

Diazoazoles, because of charge polarization and potential bifunctional reactivity of the derived betaine, react with dipolarophiles to give cycloaddition products. Generally all the diazoazoles react with electron-rich, unsaturated derivatives. The cycloaddition reaction with isocyanates is readily observed in the case of the reactive 3-diazopyrazoles, but it is much slower with other diazoazoles. By contrast, reaction with ylides and diazoalkanes is only observed for 3-diazopyrazoles and 3-diazoindazoles. 

The hydrogenation step following hydroformylation serves two important purposes. It reduces the aldehyde intermediate product to the desired primary alcohol functional group, which is the primary site of reactivity of the polyol with isocyanates. It also reduces the residual olefins in the FAMEs to saturated hydrocarbons, thus eliminating the pathway to Hock degradation and odor development, which is inherent to other processes that leave fatty acid unsaturation in the polyols. This step eliminates the typical vegetable oil odor from the final namral oil polyols of this process. 

Esters are completely reduced to alcohols whde unsaturated esters are converted to unsaturated alcohols. Other reduction reactions include conversion of phenyl isocyanate to N-methylanihne ... 

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