2.5- Dimethylfuran, Diels-Alder

The use of silica-supported Lewis acids as catalysts for the Diels-Alder reactions of 2,5-dimethylfuran leads to fairly good yields of adducts [28]. Solid supports such as... 

Dewar thiophenes 46 and 47 are in equilibrium 47 Diels-Alder reaction of this mixture with 2.5-dimethylfuran leads to complete conversion of the mixture, but with the formation of only one product 51, derived from the reaction of isomer 47 47... 

Diels-Alder reaction.1 The first step in a synthesis of citreoviral (5), a metabolite of Penicillium citreoviride, from 2,4-dimethylfuran (2) is a Diels-Alder reaction with 1, to give a 7 5 mixture of endo- and exo-adducts (3). Both are converted in 3 steps to the diol (4), a precursor to 5. 

Perfluoroalkyl-substituted propynoates and furans react to give Diels-Alder adducts. The success of the subsequent retro process depends on the substitution pattern of the furan ring system. The adducts of unsubstituted furan are thermally relatively stabile, whereas the [4 + 2] cycloadducts of 2,5-dimethylfuran readily undergo a thermally induced retro-Diels-Alder reaction to give the 3-trifluoromethylfuran in high yield [91JFC(53)285] (Scheme 89). 

Diels-Alder cycloadditions involving thiete sulfones as dienophiles occur with butadiene,cyclopentadiene, 1,2,3,4-tetraphenylcyclopentadiene, anthracene. tetraphenylcyclopentadienone, l,3-diphenyl-2H-cyclopenta[l]-phen-anthrene-2-one, a-pyrone, l-(Af,Af-dimethyl)- and l-(7V,A -diethyl)-l,3-butadiene, furan, 2,5-dimethylfuran, l,3-diphenylisobenzofuran, isobenzofuran," and l,3-diphenylnaphtho[2,3-c]furan. Generally, thiete... 

The plinols (355), thermal cyclization products of linalool (28) (Vol. 2, p. 61, Refs. 208 and 216 Vol. 4, p. 494, Ref, 285), have been synthesized by a new route, starting with Diels-Alder additions to 2,5-dimethylfuran. The adduct with maleic anhydride was said to be exo-, 356, although no evidence was given, and the only reference quoted concerning this compound does not refer to stereochemistry. The adduct of furan and maleic anhydride is indeed known to be entirely converted to the exo-isomer after initial formation of the endo-... 

Periodate cleavage of an oxabicyclic diol was also a key step in the synthesis of citreoviral from the Diels-Alder adduct of 2,4-dimethylfuran and vinylene carbonate [136]. 

The Diels-Alder reaction of maleic anhydride with 3,4-dimethoxyfuran affords endo- and exo-adducts at about the same rate, in contrast to furan, where the endo-isomer is the product of kinetic control. In both cases the exo-adduct is thermodynamically more stable. 3,4-Dimethoxyfuran and p-benzoquinone give the eiufo-compound (37), whereas in the reaction with 2,3-dimethyl-1,4-benzoquinone only the exo-adduct (38) was detected. The Diels-Alder adduct (40) of methyl acrylate to 2-amino-3-cyano-4,5-dimethylfuran (39) is readily... 

In another approach, Shiramizu and Toste describe a method for converting 2,5-dimethylfuran into TA by cycloaddition with acrolein followed by aromatization and decar-bonylation [146]. Using Lewis acid catalysts and temperatures as low as —55 °C, the authors were able to obtain (non-isolated) yields of the Diels-Alder adducts in up to 75%. 

Shiramizu, M. and Toste, F.D. (2011) On the diels-alder approach to solely biomass-derived polyethylene terephthalate (PET) Conversion of 2,5-dimethylfuran and acrolein into p-Xylene. Chemistry A European Journal, 17 (44), 12452-12457. 

The naked sugar approach, developed and successfully applied by Vogel and co-workers for the synthesis of many natural products, was applied also for the synthesis of polypropionate chains. Thus, the Diels-Alder reaction between 2,4-dimethylfuran 261 and enantiomerically pure... 

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