Dimerization acrylates

The lesser stereoselectivity observed for the acrylate dimers [2c] in THF is readily understood in terms of the lesser coordinative ability of the carboalkoxy group compared to that of pyridine ( 7) (Table 3). 

The data listed in Table 10.17 give clear evidence of the enormous rate acceleration in aqueous solution, in accordance with all previous kinetic reports [51, 61, 72), particularly for the corresponding cyclopentadiene cycloadditions [73]. The highest values for the kinetic ratio ks/fcref (> 1000) are observed for reactions involving the least hydrophilic molecules (HCCP -1- styrene, isoprene I-methyl acrylate, dimerization of isoprene). Intermediate values are found in reactions involving ketones. 

The head-to-head dimerization of methyl acrylate (MA) to dimethyl A2- and A3-dihydromuconate (DHMs) [Eq. (11)] leads to an intermediate which can be transformed to nylon-6,6 via adipic acid. An scC02-[BMIM][BF4] biphasic system for methyl acrylate dimerization using a catalyst formed from [Pd(acac)2], [Bu3PH][BF4], and [Et20H][BF4] has recently been reported [59]. 

BaUivet-Tkatchenko et al. [35] reported methyl acrylate dimerization in IL-scCOj biphasic systems showing results equivalent to those obtained in monophasic ones. SCCO2 can also be used as a Cl building block. As an example, Kawanami et al. [36] reported the synthesis of cychc carbonates from epoxides and scCOj using IL as catalysts (Figure 18.5). With the use of CO2 in the supercritical state, quantitative conversion with 100% selectivity was achieved within 5 min and with turnover frequencies (TOFs) 77 times larger than those previously reported. 

Acrylated dimers and trimers of diisocyanates are described in other formulations. These, for instance, were illustrated in another Japanese patent as follows... 

M. Brookhart et al. - Implication of Three-Center, Two-Electron M-H-C Bonding for Related Alkyl Migration Reactions Design and Study of an Ethylene Polymerization Catalyst, /. Am. Chem. Soc. 107, 1443,1985 Mechanism of Rh(III) Catalyzed Methyl Acrylate Dimerization, ibid. 114,4437,1992. 

Table II shows that in the presence of Lewis acids, acrylate dimerization by [(C2H4)2RhCl]2 occurred at 90 C. No dimer was formed at this temperature in the absence of Lewis acid. The reactions listed in Table II also include a small amount of methanol as a proton source (see below). It can be seen from Table II that the yield of dimer is extremely dependent...

Dimer yields using the ZnQ2-promoted (PhCN)2PdCl2 catalyst system were initially found to vary erratically from run to run. This irreproducib-ility was traced to low levels of methanol in commercial methyl acrylate. As shown in Table HI, the presence of a proton somce such as methanol significantly increased the yield in Rh-catalyzed acrylate dimerization. 

Nugent and McKinney found that the distribution of linear product isomers from acrylate dimerization is markedly dependent on the combination of catalyst and promoter used (Table IV). For instance, changing the promoter from FeCl, to SnCl4 in the Rh-catalyzed dimerization... 

Also cationic nickel complexes have been studied in acrylate dimerization [57]. The catalyst [NiYL( 7 -C3H5)] was investigated with a broad variation of the anion Y and the phosphorus ligand L. As is shown in Table VI, the trimethylphosphine is by far the best ligand, followed by other phosphines with linear alkyl substituents such as PBu or POct . The sterical property of the ligand seems to have a great influence on the activity of the catalyst, whereas the sdectivity is not influenced remarkably. In all experiments about 85—90% linear dimers were formed with dimethyl raAW-hex-2-enedioate as the main product. 

In spite of the novel encouraging results in acrylate dimerization, the technical exploitation is still a great challenge. The best turnover in the nickel catalyzed reaction are 400 cycles per nickel atom, obtained in a batch reactor after a reaction time of 72 h. All experiments showed that the catalyst decomposes during the reaction. 

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. 

Jap-KIingermarm reactions, 4, 301 oxidation, 4, 299 reactions, 4, 299 synthesis, 4, 362 tautomerism, 4, 38, 200 Indole, 5-amino-synthesis, 4, 341 Indole, C-amino-oxidation, 4, 299 tautomerism, 4, 298 Indole, 3-(2-aminobutyl)-as antidepressant, 4, 371 Indole, (2-aminoethyl)-synthesis, 4, 278 Indole, 3-(2-aminoethyl)-synthesis, 4, 337 Indole, aminomethyl-reactions, 4, 71 Indole, 4-aminomethyl-synthesis, 4, 150 Indole, (aminovinyl)-synthesis, 4, 286 Indole, 1-aroyl-oxidation, 4, 57 oxidative dimerization catalysis by Pd(II) salts, 4, 252 Indole, 1-aroyloxy-rearrangement, 4, 244 Indole, 2-aryl-nitration, 4, 211 nitrosation, 4, 210 synthesis, 4, 324 Indole, 3-(arylazo)-rearrangement, 4, 301 Indole, 3-(arylthio)-synthesis, 4, 368 Indole, 3-azophenyl-nitration, 4, 49 Indole, 1-benzenesulfonyl-by lithiation, 4, 238 Indole, 1-benzoyl photosensitized reactions with methyl acrylate, 4, 268 Indole, 3-benzoyl-l,2-dimethyl-reactions... 

Whilst the aliphatic nylons are generally classified as being impact resistant, they are affected by stress concentrators like sharp comers which may lead to brittle failures. Incorporation of mbbers which are not soluble in the nylons and hence form dispersions of rubber droplets in the polyamide matrix but which nevertheless can have some interaction between mbber and polyamide can be most effective. Materials described in the literature include the ethylene-propylene rubbers, ionomers (q.v.), polyurethanes, acrylates and methacrylates, ABS polymers and polyamides from dimer acid. 

Water-soluble polymers obtained through a radical polymerization [e.g., poly(acrylic acid) PAA] often contain sodium sulfate Na2S04 as a decomposition product of the initiator. The peak of Na2S04 is eluted before the dimer. In the interpretation of the chromatogram, a typical GPC program has to be truncated before the Na2S04 peak, or at a Mpaa value of about 200. The calibration curve in this region can be flattened by an additive small pore column as well, but the principle problem remains unsolved. 

When methyl 2-(indol-2-yl)acrylate derivative (22a) reacted with A-methoxy-carbonyl-l,2-dihydropyridine (8a) in refluxing toluene, in addition to the dimer of 22a (25%), a mixture of the expected isoquinculidine 23a and the product 24a (two isomers) was obtained in 7% and 45% yields, respectively (81CC37). The formation of 24a indicates the involvement of the 3,4-double bond of dihydropyridine. Similarly, Diels-Alder reaction of methyl l-methyl-2-(indol-2-yl)acrylate (22b) with 8a gave, in addition to dimer of 22b, a mixture of adducts 23b and 24b. However, in this case, product 23b was obtained as a major product in a 3 2 mixture of two isomers (with a- and (3-COOMe). The major isomer shows an a-conhguration. The yields of the dimer, 23b, and 24b were 25%, 30%, and 6%, respectively. Thus, a substituent on the nitrogen atom or at the 3-position of indole favors the formation of the isoquinuclidine adduct 23. 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

Acrylic textile fibers are primarily polymers of acrylonitrile. It is copolymerized with styrene and butadiene to make moldable plastics known as SA and ABS resins, respectively. Solutia and others electrolytically dimerize it to adiponitrile, a compound used to make a nylon intermediate. Reaction with water produces a chemical (acrylamide), which is an intermediate for the production of polyacrylamide used in water treatment and oil recovery. 

The condensation of arylsulfonyl acetonitriles 369a-c with 22a proceeds via addition of the in-situ formed anion 370 to the arylsulfonyl acetonitriles 369 to afford the dimers 371, in 69-94% yield, and hexamethyldisiloxane 7 [136]. Furthermore, y9-dicarbonyl compounds such as ethyl acetoacetate 372 a or ethyl benzoyl-acetate 372b are O-silylated by 22 a or 22 c to rather stable alkyl 3-O-trimethylsilyl-oxycrotonoate 373a and alkyl 3-0-trimethylsilyloxy-3-phenyl acrylate 373b [130]. Aliphatic nitro compounds such as nitromethane are O-trimethylsilylated and further transformed into oligomers [132] (cf Section 7.6) and are thus unsuitable reactants for silylation-C-substitutions (Scheme 4.50). 

Palladium(II) acetate was found to be a good catalyst for such cyclopropanations with ethyl diazoacetate (Scheme 19) by analogy with the same transformation using diazomethane (see Sect. 2.1). The best yields were obtained with monosubstituted alkenes such as acrylic esters and methyl vinyl ketone (64-85 %), whereas they dropped to 10-30% for a,p-unsaturated carbonyl compounds bearing alkyl groups in a- or p-position such as ethyl crotonate, isophorone and methyl methacrylate 141). In none of these reactions was formation of carbene dimers observed. 7>ms-benzalaceto-phenone was cyclopropanated stereospecifically in about 50% yield PdCl2 and palladium(II) acetylacetonate were less efficient catalysts 34 >. Diazoketones may be used instead of diazoesters, as the cyclopropanation of acrylonitrile by diazoacenaph-thenone/Pd(OAc)2 (75 % yield) shows142). 

Furthermore, Rhg(CO)16, which can be used advantageously for cyclopropanation of more electron-rich alkenes, furnished only insignificant amounts of cyclopropane from acrylonitrile or ethyl acrylate and ethyl diazoacetate from methacrylonitrile and ethyl diazoacetate, equally low yields of vinyloxazole, cyclopropane and carbene dimers resulted (Scheme 20)145). The use of Rh2(OAc)4 or [Rh(CO)2Cl]2 as catalysts did not change this situation. 

Initiation of MMA polymerization by complexes such as (192) was shown to proceed via a bimetallic bis(enolate) intermediate, arising from the dimerization of a radical anion.478" 80 Such a mechanism481,482 explains why efficiencies with such initiators (calculated from polymer molecular weights) are always <50%. Using a similar methodology, the bimetallic bisallyl complex (198) was shown to polymerize MMA in a living fashion (Mw/Mn 1.1) and triblock copolymers with methacrylate and acrylate segments have been prepared. 

As in the case of dimerizations, MCP derivatives are known to undergo metal-catalysed [2 + 2] codimerizations with other alkenes in a few cases [2]. The examples are limited to strained olefins, such as norbornadiene (572) (Scheme 79) [152] and cyclobutene (574) (Scheme 80) [153], and to alkyl acrylates (Table 46) [154] and always compete with the alternative [3 + 2] addition of TMM species. 

Alkyl 2-(hydroxymethyl)acrylates are versatile functionalized monomers and synthetic building blocks. Conventional preparations employ the Baylis-Hillman reaction which involves the addition of formaldehyde to the parent acrylate ester, catalyzed by l,4-diazabicyclo[2.2.2]octane (DABCO). These reactions typically take several days at room temperature, but can be achieved within minutes in the CMR and MBR (Scheme 2.4). Rapid heating under pressure prevents loss of formaldehyde. Subsequent cooling limits hydrolysis of the product, as well as dimerization and polymerization [33],... 

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