Dimethylfumarate

Hydroxy-THISs react with electron-deficient alkynes to give nonisol-able adducts that extrude carbonyl sulfide, affording pyrroles (23). Compound 16 (X = 0) seems particularly reactive (Scheme 16) (25). The cycloaddition to benzyne yields isoindoles in low- yield. Further cyclo-addition between isoindole and benzyne leads to an iminoanthracene as the main product (Scheme 17). The cycloadducts derived from electron-deficient alkenes are stable (23, 25) unless highly strained. Thus the two adducts, 18a (R = H, R = COOMe) and 18b (R = COOMe, R = H), formed from 7, both extrude furan and COS under the reaction conditions producing the pyrroles (19. R = H or COOMe) (Scheme 18). Similarly, the cycloadduct formed between 16 (X = 0) and dimethylfumarate... 

Dipolar reactivity of 5-mercapto-THISs has only been demonstrated for 16 (X = S), which, like its oxygen analog, produces with dimethylfumarate, 17. and with phenylisothiocyanate, 21 (25). Compound 16 (X = S) does not react with other typical dipolarenophiles (25). 

Stereospecific addition of diazomethane is observed with dimethyl di-methylmaleate (7) and dimethyl dimethylfumarate (10). ... 

Various o-quinodimethanes, generated in situ from o-alkenylbenzyltributyl-stannane precursors, have been used to synthesize functionalized polycycles by Diels Alder reaction with maleic anhydride, methylacrylate, dimethylfumarate and N-phenyl maleimide in the presence of electrophiles [37] (Scheme 2.16). 

Irradiation of crystalline dimethylfumarate leads selectively to cyclobutane (114), one of four possible isomers(ll9) ... 

These results, which correspond to stereospecific cis addition of hydrogen to the double bond, stand in direct contradiction to the report st> by Elving and coworkers that dimethylmaleic acid 112, R = H) affords dl-113 (R = H) exclusively and that dimethylfumaric acid affords only meso-113 (R = H). The latter results correspond of course to stereospecific tram addition of hydrogen across the double bond. Camilli, like Homer and R6der, however, observed c/s-addition of hydrogen, albeit in a slightly different system, 18> ... 

The vinylic carbon-tellurium bond in 3-129 can easily be cleaved by a tributyltin radical to afford vinyl radical 3-131, which can undergo further transformations as hydrogenation or C-C-bond formation, for example with dimethylfumarate in a (Z)-selective mode. 

The reversible redox-induced transformation of the octahedral Rh(I)-dimethylfumarate complex [RhH(Me02CCH=CHC02Me)(triphos)] to the corresponding Rh(III)-succinyl derivative [Rh CH(C02Me)CH2 (C02Me) (triphos)]2+, illustrated in Scheme 9, involves a mechanism more complex than simple hydrogen atom abstraction. 

The Rh(I)-dimethylfumarate complex undergoes an irreversible (two-electron) oxidation, that generates in the reverse scan a cathodic profile completely identical to that of the Rh(III)-succinyl derivative, Figure 21a. 

In fact, the latter displays a first (one-electron) reversible reduction followed by a second irreversible reduction that in turn shows, on the reverse scan, the oxidation peak of the Rh(I)-dimethylfumarate complex, Figure 21b. The complete interconversion process is illustrated in Scheme 10. 

The formation of meso-dimethylsuccinic acid from dimethylmaleic acid and the racemic mixture from dimethylfumaric acid implies that both hydrogen atoms add to the same side of the unsaturated molecule 11). Bourguel (12) also noted that disubstituted acetylenes yielded initially cis-ethylenes but that trans isomers were formed if the hydrogenations were protracted. 

Decomposition of the trimethylsilyl diazoacetate 133 with a ruthenium cluster in the presence of benzaldehyde and dimethylfumarate led to formation of the THE derivative 135 in 54% isolated yields. The ruthenium catalyst proved superior to all standard rhodium complexes for this transformation. 

The Mg2+ ion also shows an acceleration effect on the photoreduction of dimethylfumarate and some other related olefins by 1-benzyl-1,4-dihydro-nicotinamide (BNAH) used as an NADH model compound via photosensitized electron transfer from BNAH to [Ru(bpy)3]2+ (Scheme 16) [160]. In this case, however, the complex formation of BNAH with Mg2+ results in an increase in the one-electron oxidation potential of BNAH [87]... 

At high concentrations of t-1, irradiation with dimethyl fumarate yields 34 and a mixture of isomeric oxetanes, 37 (76). Based on the concentration dependence of truxinate and oxetane formation, it was proposed that oxetane formation occurs upon reaction of the t-1 excimer with dimethylfumarate (eq. 18). 

Table 6. Reaction Half-Lives as a Function of Solvent in the Synthesis of 87 from 20 and Dimethylfumarate...

Notes Abbreviations for dienophiles NPM = JV-phenylmaleimide DMFum = dimethylfumarate MeAcr =... 

A-Phenylmaleimide yielded compound (148) from reaction with the ylide (7) and other m-bis (areneazo)ethylenes were also investigated. The stereospecificity of the reaction was probed using dimethylmaleate and dimethylfumarate as dipolarophiles, yielding compounds (149) and (150), respectively. 

Pandey and coworkers have studied the DCN-sensitized oxidation of N-hydroxyamines without prior removal of dissolved oxygen, to nitrone intermediates. Trapping the nitrones by dimethylfumarate (282) gave the corresponding cycloadducts in good yields (Scheme 66) [317]. 

Since olefin molecules can have stereoisomers (cis and trails Z and E), the interesting stereochemistry, which is not only stereoselectivity but also stereospecificity, of their hydrogenation should be observed when the products also have stereoisomers d, I and meso threo and erythro). However, only in a few works could stereospecificity be observed. Dimethylmaleic and dimethylfumaric acids are reduced at a mercury cathode to form d, I and meso a, a -dimethylsuccinic acids, respectively. This is direct evidence that this hydrogenation proceeds through Ivans addition of hydrogen. 

A detailed study of the photochemical addition of kbellin, a photobiologically active furochromone, to dimethylfumarate has been investigated. The (2+2)-eyeloaddition encountered in this... 

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