Acrylates addition reactions

Figure 3 shows the simple case of a clock reaction competing with hydrogen atom transfer from tin hydride. If one wished to determine, for example, the rate of addition of a primary alkyl radical to an activated alkene such as an acrylate, then the reaction could be run at low concentrations of tin hydride such that both the radical clock and its rearrangement product reacted predominantly with the alkene. The products of the acrylate addition reaction are deactivated with respect to addition to another acrylate molecule, and one could control concentrations such that these adducts reacted primarily with the tin hydride (Scheme 3). In this case, then, one would analyze for the acrylate addition products of the unrearranged and rearranged radicals.

Dimer formation, which is favored by increasing temperature, generally does not reduce the quaHty of acryhc acid for most applications. The term dimer includes higher oligomers formed by further addition reactions and present in low concentrations relative to the amount of dimer (3-acryloxypropionic acid). Glacial acrylic acid should be stored at 16—29°C to maintain high quaHty. 

Methacryhc acid and its ester derivatives are Ctfjy -unsaturated carbonyl compounds and exhibit the reactivity typical of this class of compounds, ie, Michael and Michael-type conjugate addition reactions and a variety of cycloaddition and related reactions. Although less reactive than the corresponding acrylates as the result of the electron-donating effect and the steric hindrance of the a-methyl group, methacrylates readily undergo a wide variety of reactions and are valuable intermediates in many synthetic procedures. 

The versatility of this reaction is extended to a variety of aldehydes. The bisphenol derived from 2,6-di-/ f2 -butylphenol and furfural, (25) where R = furfuryl (13), is also used as an antioxidant. The utility of the 3,5-di-/ f2 -butyl-4-hydroxyben2yl moiety is evident in stabili2ets of all types (14), and its effectiveness has spurred investigations of derivatives of hindered alkylphenols to achieve better stahi1i2ing quaUties. Another example is the Michael addition of 2,6-di-/ f2 -butyl phenol to methyl acrylate. This reaction is carried out under basic conditions and yields methyl... 

Michael addition reaction of 1-hydroxytryptamines to Q ,/3-unsaturated carbonyl compounds is worthy of note (99H2815). Addition of Ab-acetyl- 1-hydroxy-tryptamine (39) to methyl acrylate and methyl crotonate in the presence of... 

Isopropyl acrylate is produced by an acid catalyzed addition reaction of acrylic acid to propylene. The reaction occurs in the liquid phase at about100°C ... 

Malacria has reported the use of epoxysilanes for intermolecular addition reactions to acrylates, acrylonitrile and vinylsulfones [56]. 

Silyl esters of trivalent phosphorus acids have been used successfully in conjugate addition reactions using acrylates,393 395 nitriles,394 amides,396 397 ketones and aldehydes,398-404 and nitro compounds.387... 

The Michael addition reaction of the serine-derived oxazolidine 326 with ethyl acrylate gave two products. The major product of the reaction was found to be the bicyclic compound 327, which was formed in 27% yield, accompanied by the unsaturated ester 328. The Dess-Martin oxidation of 327 resulted only in formation of the elimination product, the 7,7a-dihydro-177, 377-pyrrolo[l,2-r ]oxazole 328 (Scheme 46) <2001JOC7555>. 

Apart from isolated reports summarized in Scheme 47, the chemistry of the fully conjugated ring systems has not been especially developed since CHEC-II(1996). In 1999, Monnier et al. reported the 1,3-dipolar cycloaddition of Reissert compound 160 with acrylates. Addition of triethylamine traps hydrofluoroboric acid and increases the proportion of milnchnone imine 160B the reaction therefore predominantly yields 1,3-adduct 161 which rearranges to 162 (Scheme 47) <1996BSB777, 1999EJ0297>. 

However, in an intriguing reaction promoted by the para-nitro groups of the aryl-sulphone (1) (Scheme 6.25), the initial Michael adduct derived from acrylic esters produces the diarylpropanoic esters (2), together with the diesters (3) (from methyl or ethyl acrylate) [39]. A similar addition-rearrangement reaction has been observed with l-aryl-2-(4-nitrobenzenesulphonyl)ethanones [40]. Additionally, reaction of the sulphonylethanone with two equivalents of the acrylic ester produces a 4-hydroxy-1,4-diarylcyclohexane-1,3-dicarboxylate. 

This experimental procedure must be followed carefully to avoid partial decomposition of ethyl a-(hydroxymethyl)acrylate. The reaction is stopped rapidly after the addition of the carbonate solution (5 min) to prevent formation of high molecular weight by-products which result from transesterification and Michael addition, both of which occur in the basic medium. However, about 25% of the product is lost. Addition of diethyl ether during cooling minimizes side reactions. 

Finally, addition reactions of the isolable phosphasilylcarbenes (13) to such electron-poor substrates as methyl acrylate, C4F9CH=CH2, and styrene afford cyclopropanes. The additions of 13a to (E)- or (Z)-p-deuteriostyrene are stereospecific, and the competitive additions of 13b to ring-substituted styrenes exhibit nucleophilic selectivity, consistent with singlet, nucleophilic carbene addition (Fig. 7.8). ... 

Acrylates, for example, contain an a, 3-unsaturated carbonyl system and as such undergo Michael addition reactions. This is believed to be the basis of the carcinogenic properties of acrylates [21]. Incorporation of a methyl (-CH3) group on the a-carbon (to provide a methacrylate) decreases the electrophilicity (i.e., reactivity) of the (3-carbon [40], hence methacrylates do not undergo 1,4-Michael addition reactions as readily. Methacrylates often have commercial efficacy similar to that of acrylates in many applications, but are less likely to cause cancer because they are less reactive. This point can be demonstrated by comparing methyl methacrylate (6), which does not cause cancer in experimental animals [41], with ethyl acrylate (7), which causes cancer in experimental animals in assays similar to those used to test 6 [42]. 

Huisgen, Szeimies, and Mobius have studied the addition reactions of aryl azides to a,/S-unsaturated esters and nitriles.1 4 Methyl acrylate (73) reacts with aryl azides to form l-aryl-4-carbomethoxy-A -triazolines in agreement with the orientation rule based on electronic effects. These A -triazolines are completely converted by base catalysis into the ring-opened isomer. Thus l-phenyl-4-carbomethoxy-A2-triazo ine (74) gives, in the presence of triethylamine at room temperature, methyl 3-aniline-2-diazopropionate (75). The A2-triazolines as well as the a-diazoesters are thermolabile. 74 is converted into l-phenyl-2-carbomethoxyaziridine (76) and 75 gives methyl 3-anilinoacrylate (77) as thermolysis product.262... 

Vinyl ester resins arc manufactured through an addition reaction of an epoxy resin with an acrylic monomer, such as acrylic acid, methaciylic add. or the half-ester product of an hydroxyalkyl acrylate and anhydride. In contrast, the polyester resins are condensation products of dibasic acids and palyhydric alcohols. The relatively low-molecular-weight precise polymer structure of the vinyl ester resins is in contrast to the high-molecular-weight random structure of the polyesters. 

The addition of azetidine (15) to DMAD proceeded exothermically to give dimethyl (l-azetidinyl)maleate (17) as a crystalline solid88 with MP, compound 16 was obtained, and the NMR spectrum of this compound was informative of the stereochemical course of the reaction, which is solvent-dependent. In aprotic solvents, only cis addition occurred, giving the trans-acrylate, whereas in methanol a mixture of cis and trans products in the ratio 2 1 was obtained. The effect of solvents on the stereospecificity of the addition reaction agrees with that usually observed for secondary amines87 but contrasts with aziridine where the trans addition competes to some degree with the cis addition even in aprotic solvents,39,88... 

The simple addition reaction in Scheme 19 illustrates how the notation is used. Ester (1) can be dissected into synthons (2), (3) and (4). Synthons for radical precursors (pro-radicals) possess radical sites ( ) A reagent that is an appropriate radical precursor for the cyclohexyl radical, such as cyclohexyl iodide, is the actual equivalent of synthon (2). By nature, alkene acceptors have one site that reacts with a radical ( ) and one adjacent radical site ( ) that is created upon addition of a radical. Ethyl acrylate is a reagent that is equivalent to synthon (3). Atom or group donors are represented as sites that react with radicals ( ) Tributyltin hydride is a reagent equivalent of (4). In practice, such analysis will usually focus on carbon-carbon bond forming reactions and the atom transfer step may be omitted in the notation for simplicity. 

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