Acrylates cyclization

CgH,oN20. Colourless crystalline solid, m.p. 121 °C. Made by reacting phenylhydrazine with ethyl acrylate to obtain the hydrazide which cyclizes to the product. Its major commercial importance is as a photographic developing agent, being used particularly in conjunction with hydroquinone. 

Barrelene was obtained via a double Diels-Alder reaction from a-pyrone with methyl acrylate (H.E. Zimmerman, I969A). The primarily forming bicyclic lactone decarboxylates in the heat, and the resulting cyclohexadiene rapidly undergoes another Diels-Alder cyclization. Standard reactions have then been used to eliminate the methoxycarbonyl groups and to introduce C—C double bonds. Irradiation of barrelene produces semibullvalene and cyclooctatetraene (H.E. Zimmerman. 1969B). 

The benzene derivative 401 by the intermolecular insertion of acrylate[278], A formal [2 + 2+2] cycloaddition takes place by the reaction of 2-iodonitroben-zene with the 1,6-enyne 402. The neopentylpalladium intermediate 403 undergoes 6-endo-lrig cyclization on to the aromatic ring to give 404[279],... 

Allylic carbonates are most reactive. Their carbonylation proceeds under mild conditions, namely at 50 C under 1-20 atm of CO. Facile exchange of CO2 with CO takes place[239]. The carbonylation of 2,7-octadienyl methyl carbonate (379) in MeOH affords the 3,8-nonadienoate 380 as expected, but carbonylation in AcOH produces the cyclized acid 381 and the bicyclic ketones 382 and 383 by the insertion of the internal alkene into Tr-allylpalladium before CO insertion[240] (see Section 2.11). The alkylidenesuccinate 385 is prepared in good yields by the carbonylation of the allylic carbonate 384 obtained by DABCO-mediated addition of aldehydes to acrylate. The E Z ratios are different depending on the substrates[241]. 

Catalysts. Silver and silver compounds are widely used in research and industry as catalysts for oxidation, reduction, and polymerization reactions. Silver nitrate has been reported as a catalyst for the preparation of propylene oxide (qv) from propylene (qv) (58), and silver acetate has been reported as being a suitable catalyst for the production of ethylene oxide (qv) from ethylene (qv) (59). The solubiUty of silver perchlorate in organic solvents makes it a possible catalyst for polymerization reactions, such as the production of butyl acrylate polymers in dimethylformamide (60) or the polymerization of methacrylamide (61). Similarly, the solubiUty of silver tetrafiuoroborate in organic solvents has enhanced its use in the synthesis of 3-pyrrolines by the cyclization of aHenic amines (62). 

Phenol reacts with some acryUc acid derivatives to produce coumaria. With 3-ethoxyacryHc acid chloride, phenol gives phenyl ethoxyacrylate that cyclizes iato coumaria on treatment with sulfuric acid (41). Coumaria is also formed by reactioa of pheaol with methyl acrylate ia acidic medium and ia the presence of air (42). 

The as-spun acrylic fibers must be thermally stabilized in order to preserve the molecular structure generated as the fibers are drawn. This is typically performed in air at temperatures between 200 and 400°C [8]. Control of the heating rate is essential, since the stabilization reactions are highly exothermic. Therefore, the time required to adequately stabilize PAN fibers can be several hours, but will depend on the size of the fibers, as well as on the composition of the oxidizing atmosphere. Their are numerous reactions that occur during this stabilization process, including oxidation, nitrile cyclization, and saturated carbon bond dehydration [7]. A summary of several fimctional groups which appear in stabilized PAN fiber can be seen in Fig. 3. 

Two-step 1,4 cycloaddition of enamines, such as was observed with methyl vinyl ketone, is not possible with acrylate or maleate esters. This is due to the fact that, following the initial simple substitution, no side-chain carbanion is available for nueleophilic attack on the a carbon of the iminium ion. Likewise two-step 1,3 eycloaddition, such as that found when alicyclic enamines were treated with acrolein, is impossible with acrylate or maleate esters because transfer of the amine moiety from the original enamine to the side chain to form a new enamine just prior to the final cyclization step is not possible. That is, the reaction between a seeondary amine and an ester does not produce an enamine. 

Due to the commercial availability of EMME in good purity, there has not been a need to develop new methods to prepare 3-anilino-acrylates therefore, only a few alternatives have been reported. One approach described thermal carbene generation from 37, and rearrangement to form 38. Cyclization in refluxing 1,2-dichlorobenzene (1,2-DCB) provided the 2, 3, 4-trisubstituted quinolines. An electron-withdrawing group (EWG) on the carbene carbon was required for this reaction, and therefore led to the EWG substitution in the 2-position of the quinoline. 

The preparation and use of derivatized Meldrum s acid has led to an alternative preparation of 2-substituted quinolines (49 and 50) and the preparation of pyridopyrimidines (52). When Meldrum s acid derivatives are used (as shown in this example) decarboxylation occurred under the cyclization conditions. Three component coupling has been used to readily assemble the desired 3-anilino-acrylate from reaction of Meldrum s acid, (EtO)3CH and an aniline (e.g. 54 or 55).< ... 

C-alkylated material 119. The cyclization of a 3-aminopyridino-methylene malonate has been shown. The formation of amino-acrylate 121 was nearly quantitative and subsequent cyclization afforded a 50% yield of the 1,5-napthyridine. Saponification and decarboxylation gave the desired 1,5-napthyridine 124 in good yield. 

Formation of the amino-acrylate of aminopyrimidine intermediates was reported. In the absence of base, alkylation occurred on the carbon and not the nitrogen, followed by cyclization to give 125. In the presence of base (EtONa), condensation occurred on the nitrogen. Cyclization under thermal conditions afforded 128. °... 

With pyrimidine systems, another anomaly occurred with which group underwent cyclization in the case of a-cyano-P-(pyrimidino)amino-acrylate. For example, cyclization of 129 occurred on the CN group providing the 5-amino-pyridopyrimidine 130. 

Cyclization of methyl 2-[2-benzoyl-2-ethoxycarbonyl-l-vinyl)amino]-3-[(4-methyl-2-pyridyl)amino]acrylate (311) afforded the 3-amino-8-methyl-4//-pyrido[l,2-n]pyrimidin-4-one derivative 312 (97JHC1511). 

Condensation of 2-quinolinecarboxaldehyde 98 with acetylacetone or ethyl acetate gave the acrylate derivatives 99 and 100, respectively. Cyclization of 99 with AC2O afforded the benzindolizine 101 (80ACSA(B)79). Reduction of 100 in presence of Adams catalyst followed by hydrolysis gave 102 (78PJC107) (Scheme 19). 

The transformation of the porphyrin intermediate 4 into a chlorin can be achieved after introduction of a C — C double bond into the 15-propanoate side chain of 4 to yield 5. The cyclization of 5 with participation of the 15-acrylic ester side chain under acidic conditions gives the chlorin 6 which is then transformed in a multistep reaction sequence into chlorophyll a. The driving force of chlorin formation from the porphyrin is believed to be the relief of steric strain at the sterically overcrowded porphyrin periphery which gives the desired trans arrangement of the propanoate side chain and the methyl group in the reduced ring. The total... 

For the construction of the I ring, the vinylic group introduced to activate the y-hydroxy epoxide moiety of 28 towards cyclization is an acrylic ester residue, which concomitantly allows cyclization on the allylic position, with formation of the tricyclic compound 29 containing the IJK fragment of the natural product, and fur-... 

It has been suggested that certain 1,5-dienes including o-divinylbenzene (23),156 vinyl acrylate (24, X 11) and vinyl methacrylate (24, X CH )120 may also undergo cyclopolymerization with a monomer addition occurring prior to cyclization and formation of a large ring. However, the structures of these cyclopolymers have not been rigorously established. 

Other examples that involve intermediate allyl cations are illustrated in Scheme 1.4. The cationic palladium(II) complex [Pd(dppp)(PhCN)2](BF4)2 coordinates the carbonyl oxygen of benzaldehyde and the activated carbonyl carbon attacks the isoprene, forming the allyl cation 10 which then cyclizes to give the 4-methyl-6-phenyl-5,6-dihydro-2H-pyran [22]. 2-Oxopropyl acrylate 11, in the presence of trimethylsilyltrifluoromethane sulfonate (TMSOTf) and methoxytrimethylsilane (MeOSMT), generates the cation 11a which is an efficient dienophile that reacts easily with the cyclohexadiene to give the Diels-Alder adduct in good yield [23]. 

Radical cyclization is compatible with the presence of other functional groups. Treatment of XCH2CON(R)-C(R )=CH2 derivatives (X = Cl, Br, 1) with Ph3SnH and AIBN led to formation of a lactam via radical cyclization. " Cyclization of N-iodoethyl-5-vinyl-2-pyrrolidinone led to the corresponding bicyclic lactam, " and there are other examples of radical cyclization with molecules containing a lactam unit " or an amide unit. Radical cyclization occurs with enamines as well. Photochemical irradiation of A,A-dialIyl acrylamide leads to formation of a lactam ring, and in this case thiophenol was added to generate the phenylthio derivative. Phenylseleno N-allylamines lead to cyclic amines. co-Iodo acrylate esters cyclize to form lactones. " ... 

A radical cyclization of a 2-chloroacyl enamine 157 was used to synthesize 2-substituted pyroglutamates 160. Usually, the radical 158 undergoes an initial 5-endo cyclization (path a) and the resulting intermediate 159 attacked electrophiles like methyl acrylate to give the pyroglutamate 160. Unexpectedly, the reaction with methyl methacrylate took another course and a seven-membered... 

The combination of CsF with Si(OMe)4 58 is an efficient catalyst for Michael additions, e.g. of tetralone 130 to methacrylamide, followed hy cyclization of the addition product to the cyclic enamide 131 in 94% yield [67]. Likewise, addition of the lactone 132 to methyl cinnamate affords, after subsequent cyclization with tri-fluoroacetic acid, the lactam 133 in 58% yield [68] whereas < -valerolactam 134, with ethyl acrylate in the presence of Si(OEt)4 59/CsF, gives 135 in 98% yield [69]. Whereas 10mol% of CsF are often sufficient, equivalent amounts of Si(OEt)4 59 seem to be necessary for preparation of 135 [69] (Scheme 3.11). 

The protic catalytic conditions are also compatible with trapping of the radicals formed after cyclization with acrylates or acrylonitriles prior to their reduction with Cp2TiCl . In this manner highly substituted alkenes for the potential preparation of modified steroids can be accessed (Scheme 19) [97]. 

Morken et al. demonstrated that the combination of [Ir(COD)Cl]2 (2.5 mol %) and P(OPh)3 catalyzed the Mannich reaction of aldimine 164 and trifluorophenyl acrylate 165 at 60 °C. Under these conditions, the initially formed Mannich product undergoes cyclization to furnish the corresponding lactam 166 in 80% with high frans-seleclivily > 20 1 (Scheme 42) [73],... 

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