3-vinyl furans

Aromatic compounds (C5H5) Aromatic nitro compounds Aromatic alcohols Vinyl furans... 

When undiluted 2-vinylfuran was added to metallic sodium (mirror or particles) an orange colour developed and some resinous material was deposited on the metal surface. On prolonged contact much of the monomer was converted into a partly-insoluble reddish resin with spectra unrelated to those of standard poly(2-vinyl-furan). Reaction of diluted monomer with sodium gave a milder interaction, but no evidence of living anionic polymerization. 

Elementary considerations indicate that with appropriate substitutions some of the reactions mentioned above can be eliminated. Indeed, when 5-methyl-2-vinyl-furan was used, no alkylation was observed, the positions C-3 and C-4 being rather unreactive16, and the polymer was a mixture of linear chains with polyunsaturations and linear saturated chains, i.e. only structures like 21, 23 and 26 were present, with a 5-methyl ring instead of the 5-unsubstituted one. When 2-isopropenylfuran was used, no hydride transfer took place since this requires a hydrogen atom in the a-position to the ring, which this monomer does not have the polymers were white and gave electronic spectra transparent down to 280 nm. Alkylation at C-5, how-... 

Of course, these conclusions do not rule out completely the occurrence of other reactions such as those listed above, but their contribution to the overall mechanism must be very small in the production of the oligomers. The dark colour of these products was attributed to hydride transfer reactions, similar in nature to those encountered in the cationic polymerization of 2-vinyl furan [see Section III-B-l-c)]. The subsequent process which transforms these oligomers into cross-linked resins was not investigated. 

Finally, 2-vinyl furan 2a displays an intermediate behaviour in that it polymerizes slowly (because "normal" radicals formed from addition to the vinyl group are relatively stabilized), but gives modest DPs and limiting yields due to the fact that the furan rings pendant to the polymer chains act as radical traps which retard the polymenzation and inhibit it above a certain concentration (equivalent to a given polymer yield). 

Recently, Spange et al. (19,20) have successfully achieved cationic graft polymerizations of vinyl ethers, vinyl furan, and cyclopentadiene onto silica, initiated by a stable ion pair formed from silanol and aiylmethyl halide, such as di(p-methoxy-phenyl)methyl chloride. The grafting of the polymer onto silica is proposed to take place via the propagation based on olefin insertion to a cation center being in a rapid equilibrium with the ion pair, as shown in Scheme 12.1.3. 

Furanodecalins can be readily obtained in good yield using intramolecular cycloadditions of simple unsaturated esters as dienophiles. The (2 ,8Z)-nonadienoate 300, when heated to 290°C was converted into the c/s-furanodecalin 301 in quantitative yield. Thermolysis of the (2E, 8 )-nonadienoate 302, gave cw-furanodecalin 301 and the trans isomer 303 in a ratio 45 55. The same methodology is equally suited to 3-vinyl furans (88TL2107). 

Azido-2-vinyl-furans, -thiophenes, -selenophenes,296 and -p-benzoqui-nones37 cyclize to the corresponding annelated pyrroles (e.g., 239). 

The few examples in which vinyl-furans take part as 4n components in intramolecular cycloadditions include that shown below. " In simpler, intermolecular cases yields are generally poor and the extra-annular mode must compete with the more usual intra-annular mode the inclusion of a bulky group at an a-position assists this differentiation. ... 

Temperaturen iiber 200° fiihren zu Hydrogenolysen17 19. Wahrend bei der Hydrierung in alkalischer Losung bereits bei 23° Ringspaltung beobachtet20 wird (Tab. 65 Nr. 39), unterdriickt Ammoniak-Zusatz beim 2-Vinyl-furan die Ringhydrierung21. Formyl- und... 

Under modified reaction conditions double bonds conjugated to heterocycles can be selectively reduced without affecting the heterocyclic system. For example, the sensitive vinyl furan 3 can be reduced with sodium in liquid ammonia/tetrahydrofuran containing five equivalents of water. After ten minutes, the reduced product 4 is obtained in excellent yield with a trans/cis ratio of > 95 58. 

Knight - Vinyl furan Diels-Alder reactions [88TL2107]... 

A purely thermal homopolymerization to high molar masses has only been proved for styrene and some of its derivatives, as well as for 2-vinyl pyridine, 2-vinyl furan, 2-vinyl thiophene, methyl methacrylate, and acenaphthylene. In contrast, vinyl mesitylene, 9-vinyl anthracene, and methyl acrylate do not polymerize spontaneously. Some of fhe thermal polymerizations proceed by a free radical mechanism others, however, do not. 

Nitro- -phenyl-vinyl]-furan 17 II 67. N-FurfuTyHden-anthranil iire 17 II 311 ... 

Reactions. Birch reduction of 2-furoic acid with lithium in liquid ammonia gives the 2,5-dihydro-compound (131) in 90% yield. Hydrogenation of the vinyl-furans (132 R = CO2H, C02Me, Ac, or COPh) in the presence of nickel bromide occurs selectively at the exocyclic double bond. Anodic methoxylation of 2-(2-thienylmethyl)-furan yields a mixture of geometrically isomeric adducts... 

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