Furan acrylates

Furfural Pentose Furfuryl alcohol, furfuryl amine, furan-acrylic acid, tetrahydrofuran, levulinic acid, maleic anhydride Chheda etal., 2007 Corma etal., 2007... 

A concise, stereodivergent synthesis of ( )-cyclophellitol (380) and its unnatural diastereomer (17 , 15 )-cyclophelli-tol (379) starting from the furan/acrylic acid cycloadduct 375 was reported recently [136]. The key intermediate was the protected diol 377. For P = benzyl, the epoxidation with mCPBA is controlled by the free allylic hydroxyl group and led, after debenzylation, to (l/ , 15 )-cyclophellitol (379) (Scheme 13.81). A protection (TBSOTf)/debenzyla-tion sequence converted cyclohexenol 377 (P = PMB) into the silyl-protected diol 378. Selective epoxidation of this diol... 

Polyesters Silicones Furanes Acrylics Soluble nylons... 

Heteroaromatics such as furan, thiophene, and even the 2-pyridone 280 react with acrylate to form 281(244-246]. Benzene and heteroaromatic rings are introduced into naphthoquinone (282) as an alkene component[247]. The pyrrole ring is more reactive than the benzene ring in indole. 

Furfural — see Furan-2-oarbaldehyde, 532 Furfuryl acetate, o -(butoxycarbonyl)-anodic oxidation, 1, 424 Furfuryi acrylate polymerization, 1, 279 Furfuryl alcohol configuration, 4, 544 2-Furfuryl alcohol polyoondensation, 1, 278 reactions, 4, 70-71 Furfuryl alcohol, dihydro-pyran-4-one synthesis from, 3, 815 Furfuryl alcohol, tetrahydro-polymers, 1, 276 rearrangement, 3, 773 Furfuryl chloride reactions... 

The furfuryl esters of acrylic and methacrylic acid polymerize via a free-radical mechanism without apparent retardation problems arising from the presence of the furan ring. Early reports on these systems described hard insoluble polymers formed in bulk polymerizations and the cross-linking ability of as little as 2% of furfuryl acrylate in the solution polymerization of methylacrylate121. ... 

Good yields and high diastereoselectivities were obtained by using zeolites in combination with Lewis-acid catalyst [21]. Table 4.7 illustrates some examples of Diels-Alder reactions of cyclopentadiene, cyclohexadiene and furan with methyl acrylate. Na-Y and Ce-Y zeolites gave excellent results for the cycloadditions of carbocyclic dienes, and combining these zeolites with anhydrous ZnBr2 further enhanced the endo diastereoselectivity of the reaction. An exception is the cycloaddition of furan that occurred considerably faster and with better yield, in comparison with the classic procedure [22], when performed in the presence of sole zeolites. 

The Diels-Alder reaction can be greatly enhanced by high pressure (Chapter 5) but the effect of pressure is generally weaker in aqueous medium than in organic solvent. Results of high pressure-mediated Diels-Alder reactions of furans and acrylates in water and dichloromethane are reported in Table 6.6 [32]. In aqueous medium the cycloadditions occur with lower yields and less diastereoselectivity than in dichloromethane and, in some cases, addition-substitution reactions were observed. 

Table 6.6 Diels-Alder reactions of furans with acrylates in water and dichloromethane under high pressure...

From the Diels-Alder Adduct of Furan and Acrylic Acid. 29... 

The first three carba-sugars were synthesized by McCasIand and coworkers. Two other carba-sugars were prepared from myoinositol, and the remaining eleven carba-sugars have been synthesized from the Diels-Alder adduct of furan and acrylic acid. Conformational assignments of the carba-sugars were established with the aid of H-n.m.r. spectroscopy. 

The Diels-Alder cycloaddition of furan and acrylic acid, in the presence of hydroquinone as a polymerization inhibitor, provided enrfo-7-oxabicy-clo[2.2.1]hept-5-ene-2-carboxylic acid - (29) in a yield of 45%. Compound 29 was found to be the most accessible and important starting-material for the synthesis of various racemic carba-sugars, as well as their enantiomers. 

All sixteen of the racemic carba-sugars predicted are known, as well as fifteen of the enantiomers. The most accessible starting-material for the synthesis of racemic carba-sugars is the Diels-Alder adduct of furan and acrylic acid, namely, e i o7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylicacid (29). Furthermore, adduct 29 is readily resolved into the antipodes, (—)-29 and (+)-29, by use of optically active a-methylbenzylamine as the resolution agent. The antipodes were used for the synthesis of enantiomeric carba-sugars by reactions analogous to those adopted in the preparation of the racemates. 

Acid, alkali, salt -l-l- Pure epoxide, furan, and acrylic cements... 

The relative reactivities of several of these 2-hetero substituted 2-cyclopropylideneacetates 4 and 53-55 as well as of the parent 2-cyclopropylidene-acetate 52 and acrylates 56a-d towards 6,6-dimethylfulvene (57) and furan (7) were determined by competition experiments [17,19] (Table 5). The endo/exo selectivity is low, but usually still higher than for simple acrylic esters. 

Schlessinger and Bergstrom146 reported some asymmetric Diels-Alder reactions of several polystyrene bound furans to which a chiral auxiliary had been attached with methyl acrylate. The adducts were obtained with de values of more than 99%, as was determined after cleavage of the adducts from the resin. 

Scheme 15. Diels-Alder reactions of cyclopropylideneacetates 1-Me, 3-X with furan (57) and 6,6-dimethylfulvene (58) and relative reaction rates compared with methyl acrylate and methyl crotonate [19,46]...

Other 2-substituted cyclopropylideneacetates of type 3-X also entered this cycloaddition (Scheme 15) [19]. The endolexo selectivity is low but usually still higher than that of simple acrylic acid esters. The relative Diels-Alder reactivities of dienophiles 1-Me and 3-X as determined by competition experiments (Scheme 15) suggest a mechanism involving either diradicals or zwitterions as intermediates [19]. Surprisingly, the 2-fluoro derivative 3-F is less reactive than the parent compound 3-H. The 2-chloro and 2-bromo derivatives 1-Me and 3-Br have similar reactivities and cycloadd to furan (57) about 16 times faster than methyl acrylate. 

The corresponding reaction with 3-(3-furyl)acrylic acid also affords a mixture of 2-chloro-3-(3-furyl)acryloyl chloride (18%), 3-chlorothieno-[2,3-6] furan-2-carbonyl chloride (101) (25%), and 3,5-dichlorothieno-[2,3-6]furan-2-carbonyl chloride (102) [Eq. (32)]. 

Approaches to oseltamivir phosphate (1) that were independent of ( )-shikimic acid as the raw material were also evaluated. The furan-ethyl acrylate Diels-Alder approach is shown in Scheme 7.8 (Abrecht et al., 2001, 2004). The zinc-catalyzed Diels-Alder reaction between furan and ethyl acrylate was heated at 50°C for 72 h to provide a 9 1 mixture favoring exo-isomer rac-43 over the enJo-isomer. The enJo-isomer was kinetically preferred, but with increased reaction times an equilibrium ratio of 9 1 was achieved favoring the thermodynamically preferred exo-isomer rac-43. The optical resolution of rac-43 was achieved via enantioselective ester hydrolysis using Chirazyme L-2 to give (—)-43 in 97%... 

Annelation of a furan ring onto a thiophene is also possible by flash vacuum pyrolysis at 650 °C of the acrylate 368 and malonate 369, which gave 2-(methylthio)thieno[3,2-/ ]furan 370 and methyl-5-(methylthio)thieno[3,2- ]furan-2-carboxylate 371, respectively, in yields of 21% and 22% <1997J(P1)2483>. 

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