Furan series

Vinyl Ethers and Vinyl Carbonyl Compounds of the Furan Series. 79... 

The monomers considered in this section possess an olefinic bond conjugated to the ring through the C-2 position. The parent compound, 2-vinylfuran, and some of its methylated homologues are probably the best understood monomers of the furan series in terms of their behaviour and peculiarities in different polymerization systems. This consideration is of course relative, i.e. the knowledge acquired on these compounds in recent years allows the formulation of certain conclusions with a high degree of confidence and this is already exceptional in the field covered by this review. 

In order to gain a better insight into these problems, a fundamental study of simple mono- and di-urethanes of the furan series was undertaken. This included the determination of their structure, properties and stability (35) and the mechanism and kinetics of their formation. The combinations investigated were furan alcohols and diols with aliphatic, aromatic and furanic isocyanates and the latter mono- and bis- derivatives with aliphatic and arylalkyl alcohols and diols. The furanic isocyanates prepared included 9 and those given below ... 

Cycloadditions of dienes with oxyallyl offer the opportunity to prepare seven-membeted ring systems. This reaction has also proved to be of importance in Ae furan series. A few examples may illustrate the value of this methodology. A tandem Pummerer rearrangement and intramolecular [4-i3]-cycloaddition with a fiiran derivative has been reported <99TL545>. For a similar reaction see <99T13999>. 

Recent work reports that the stability of the sulfur heterocycles increases from 2 to 14 analogous investigations in the benzo[c]furan series would... 

The question may arise as to whether the diene moiety of the benzene ring of benzo[c]furan may participate in a Diels-Alder reaction (Eq. 11). Such a reaction seems not to be known in the simple benzo[c]furan series, but... 

Remarkably, the stability of the molecular ion associated with the furan and benzofuran nuclei is preserved into the benzo[c]furan series. For the 1,3-diphenyl compound the fragmentation path is believed to be as shown in Scheme 12, the molecular ion being by far the most abundant (760MS258). 

Tautomerism can be used to examine aromaticity when one tautomer possesses an aromatic nucleus and the other does not. The method has been very useful, e.g. in the pyridine series, but has not been rigorously applied in the furan series so discussion is mainly qualitative. The field has been thoroughly surveyed (63AHC(2H), and updated for furans <82AHC(31)237). 

Few simple amines are known in either the furan or the benzo[Z>]furan series. Simple nitrofurans on attempted reduction by mild chemical methods suffer what is probably a deaminative degradation. Similarly, attempted reduction of 2-nitrobenzo[6]furan affords not the amine but the product of its hydrolysis, benzofuran-2(3/f )-one. 

Grignard reagents are difficult to prepare in both the furan and benzo[f ]furan series and their use has been superseded by the more tractable lithio compounds. Bromofurans are best converted into the Grignard reagents by treatment with a copper-magnesium alloy in THF (80JOC3125). 

Also in the furan series Stradins and his co-workers have demonstrated288-290 thatp for the correlation of polarographic reduction... 

By the reaction of isatins with alkyl hetaryl ketones it is possible to obtain various 2-hetaryl-substituted 4-quinolinecarboxylic acids. Thus, in the presence of aqueous solutions of alkalis ketones of the furan series 103 react with isatins 59 with the formation of acids 104 containing a furyl substituent [12, 103, 104],... 

Synthesis and properties of unsaturated nitro compounds of the furan series 93UK184. 

Synthesis and reactions of nitroalkyl derivatives of the furan series 92MI20. 

Synthesis, structure, and properties of vicinal hydroxy-, mercapto-, and hydroselenoaldimines of the furan series 92MI22. 

As in the furan series, the loss of an OH or an -OR group is very favored in pyrrole carboxylic acids and esters, (53)->[51]. The presence of an N—H group in a-pyrrole carboxylic esters causes also the elimination of an ROH fragment,41 (53)->[54]. 

For the most part, the cyanides of heterocyclic compounds are similarly prepared by the action of alkali cyanides or cuprous cyanide on side-chain or nuclear halogen atoms, respectively. Several notable exceptions are found in the furan series. Thus, the product from the reaction of... 

---