Vinyl acetate electron rich double bond

The first route relies on the ROP of cyclic ketene acetals [1-3]. The electron-rich double bond is prone to react with radicals and electrophiles. Therefore, this class of monomers undergoes cationic and radical polymerization. For example, radical initiators react with the double bond to provide a new tertiary radical (Fig. 2). Two distinct mechanisms of polymerization can then take place direct vinyl polymerization or indirect ring opening of the cycle accompanied by the formation of a new radical, which is the propagating species (Fig. 2). The ester function is formed... 

When divinyl carbinols are heated with dimethylacetamide dimethyl acetal (4), the less substituted and less electron-rich double bond engages in the rearrangement (Scheme 7.13, Eqs. 1 and 2) [29]. Vinyl-propargyl carbinols were found to rearrange with preferential participation of the double bond (Eq. 3) [30]. For another case of a highly regjoselective Eschenmoser-Qaisen rearrangement see Scheme 7.16, Eq.4[31]. 

The requirements for the olefins are not severe as electron-poor double bonds will not react maleic anhydride is completely inert to the reactive SF5Br at 100°C. Electron-rich double bonds (1,3-butadiene, vinyl acetate, B,B-bis-ethoxy ethyl acrylate) are so reactive that it is difficult to obtain any SF5X adducts (instead XF addition products are formed) (27,29). 

In addition to alkenes or compounds with strained double bonds, 1,2,4-triazines react readily with electron-rich dienophiles such as enol ethers, enamines, enaminones, vinyl silyl ethers, vinyl sulfides, vinyl acetate, and ketene derivatives (see also Ilouben-Weyl, Vol. E7b, p 471 ff). It has been shown195,403,404 that oxo compounds and catalytic amounts of amines can be used instead of enamines however, water formed in the reaction can result in the formation of side products.403... 

Aromatic and aliphatic acyl isocyanates participate in a similar range of [4 + 2] cycloadditions although [2 + 2] and simple addition reactions often are observed. The acyl isocyanate substituents may determine or alter the observed course of the reaction, and the substituent effects have been detailed in extensive reviews.7,71 Observed [4 + 2] cycloadditions of acyl isocyanates with selected olefins, p-quinones, allenes, the carbon-carbon double bond of ketenes, electron-rich acetylenes, imines, dianils, ethy-lenediimines, enamines, enol ethers, ketene acetals, carbodiimides, azirines, and vinyl sulfides have been described.7 0 The reaction of aromatic acyl isocyanates with carbodiimides is not a simple, direct [4 + 2] cycloaddition but proceeds by a kinetic [2 + 2] cycloaddition followed by a subsequent rearrangement to provide the observed [4 + 2] cycloadduct [Eq. (40)].97... 

The semiempirical Alfrey-Price Q and e values for vinyl acetate are, respectively, 0.026 and —0.22 [226]. With some exceptions, the reactivity of the higher vinyl esters is similar to that of vinyl acetate and is reflected in similarity of their Q and e values. From these values one can qualitatively conclude that compared to styrene, the vinyl acetate double bond is slightly more electron rich and that there is comparatively little resonance interaction... 

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