Methyl 2.3-butadienoate

Methyl 2,3-butadienoate can undergo 1,3-dipolar cycloaddition with nitrones leading to the formation of 528, which would undergo homolytic cleavage of the N-O bond followed by radical rearrangement and coupling to afford benzazepinone 531 [239]. 

In 1985, Cristiau et al. reported that the reaction of methyl 2,3-butadienoate with PPh3 followed by the addition of Nal afforded phosphonium iodide 532, which makes the y-carbon prone to nucleophilic attack, leading to the formation of 4-meth-oxy-2-enonate 533 [197a]. 

Occasionally, molecular mechanics calculations provide a rationale when FMO theory fails to account for a given regiochemical outcome.For example, cycloaddition of C-phenyl-Af-methyl nitrone to methyl 2-methyl-2,3-butadienoate leads exclusively to the S-exo-methylene cycloadduct, as one would expect based upon FMO theory. In contrast, C7-phenyl- -r-butyl nitrone affords only the 4-exomethylene isoxazolidine, a result which clearly cannot be in accord with the same principles (Scheme 12). Molecular mechanics calculations, carried out under the assumption that the relative energy differences between the products parallel the energy differences between transition states, were in accord with the experimental results, suggesting that the difference in behavim- between the two nitrones may have a steric rather than an electronic origin (Table 10). ... 

Methyl-o-benzoquinone, 76, 251 N-Methylbenzylamine, 406,485 Methyl-N-benzylcarbamate, 343 B-Methyl-9-borabicydononane, 310 Methyl 2,3-butadienoate, 306-307... 

The normal aza-MBH adducts 40 could be formed in moderate yields in the PPhs-catalyzed reaction between methyl 2,3-butadienoate and A -(ethoxy-carbonyl)benzaldimine, while only trace normal aza-MBH adducts 41 were afforded for DABCO-catalyzed reactions of A-tosylated imines with ethyl 2,3-butadienoate (Scheme 1.19). These results show that the reactivities of both imines and catalysts influence the final products using the same starting materials. 

The phosphine-catalysed addition of oxygen, nitrogen, and carbon nucleophiles to ethyl 2-methyl-2,3-butadienoate (189), affording (190), is believed to proceed via an umpolung mechanism, which is portrayed in Scheme 3. A different mechanism has been proposed for sulfur nucleophiles. 

Since 3-methylenecyclobutane-l,2-dicarboxylic anhydride is easily converted to 3-methyl-2-cydobutene-l,2-dicarboxylic acid, it is an intermediate to a variety of cyclobutenes. The dimethyl ester of 3-methylenecyclobutane-l,2-dicarboxylic acid is also a versatile compound on pyrolysis it gives the substituted allene, methyl butadienoate, and on treatment with amines it gives a cyclobutene, dimethyl 3-methyl-2-cyclobutene-l,2-di-carboxylate. ... 

METHYL BUTADIENOATE (Butadienoic acid, methyl ester)... 

The checkers used a 10-mm. x 0.76-m. Nester spinning band still and obtained material having 1.4620 that could not be purified by redistillation. Analysis by vapor-phase chromatography (silicone gum rubber, 20% w/w on firebrick, 120-cm. x 6-mm. outside diameter column at 125°) showed this material to be 95% methyl butadienoate contaminated by small amounts of two other materials. 

Carbonylation of propargylic carbonates proceeds under mild neutral conditions (50 °C, I-10 atm) using Pd(OAc)2 and Ph ,P as a catalyst, yielding the 2,3-alkadienoates 18 in good yields[9,10]. The 2.3-alkadienoates isomerize to 2,4-dienoates during the reaction depending on the solvents and reaction time. 2-Decynyl methyl carbonate is converted into methyl 2-heptyl-2,3-butadienoate (19) in 82% yield. 

The method used is described by Drysdale, Stevenson, and Sharkey.4 The methyl ester of butadienoic acid has not been described previously, but the free acid contaminated by 2-bu-tynoic acid has been prepared by Wotiz, Matthews, and Lieb 5 by carbonation of propargylmagncsium bromide. Ethyl butadienoate has been prepared by Eglinton, Jones, Mansfield, and Whiting by alkali-catalyzed isomerization of ethyl 3-butynoate prepared from 3-butynol by chromic acid oxidation and esterification. 

Butadiene, 1,4-diphenyl-, 40, 36 Butadienoic acid, methyl estfr, 43, 71... 

Butadienoate esters undergo AICI3 and EtAlCh catalyzed stereospecific [2 + 2] cycloadditions with a wide variety of alkenes to give alkyl cyclobutylideneacetates in good yield. The stereospecificity and ratios of ( )- and (Z)-isomers suggest a [ 2 + v2a] cycloaddition of the ester-Lewis acid complex to the alkene analogous to the cycloaddition of ketenes with alkenes. Similar results are obtained with methyl 2,3-pentadienoate, methyl 4-methyl-2,3-pentadienoate and methyl 2-methyl-2,3-butadi-... 

The reaction of methyl 1,2-butadienoate with C-methyl-N-phenyl nitrone (Scheme 16) leads to a single diastereoisomer and is believed to take place through a transition state (13) which places the methoxycar-bonyl and phenyl groups above one another, - thereby allowing maximal ir-overlap (attractive van der Waals interaction). To do so requires that the ( )-form of the nitrone exist in solution and that it react faster than the (Z), both being reasonable suggestions vide supra). 

Formation of these products can be understood by assuming that the carbonylation of propargyl alcohol under high pressure involves two different reaction pathways. One is the Pd(0)-catalyzed carbonylation and the other is the Pd(II)-catalyzed oxidative carbonylation 2,3-Butadienoate (80) is a primary product of the Pd(0)-catalyzed carbonylation, but further attack by carbon monoxide at the central sp carbon of 80 under high carbon monoxide pressure yields itaconate (81) as the dicarbonylation product. Formation of aconitate (83) is explained by the oxidative dicarbonylation of a triple bond with Pd(II) species, followed by Pd(0)-catalyzed allylic carbonylation. As a supporting evidence, methyl aconitate (83) was... 

Gillmann et al. (94SC2133) (Scheme 148) found a convenient method to prepare methyl 2-bromo-2,3-butadienoate 540 via oxidative ring cleavage of 4-bromopyr-azol-3-one 539 using lead tetraacetate and boron trifluoride etherate in 59% yield. Compounds such as 540 are valuable building blocks for the synthesis of 2-aryl and 2-alkenyl substituted alka-2,3-dienoates via palladium-catalyzed cross-coupling reactions. 

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