Feist-Benary synthesis

D. From Feist-Benary Synthesis (Haloketone Reactions).174... 

Finally, Scharf and Wolters report a method said to be superior to both the Paal-Knorr synthesis (starting materials more easily accessible) and the Feist-Benary synthesis (freer choice for 3-substituent). Thermal rearrangement-elimination by alkylated dioxolanes at 230 C gives alkyl substituted furans. Yields can be nearly quantitive since the only serious by-products also give the furans under proton-catalyzed thermolysis (Scheme 25).124 Photochemical methods are outlined in Section VII. 

Standard heterocyclic syntheses tend to have a name associated with them and it is simply not worth while learning these names. Few chemists use any but the most famous of them we will mention the Knorr pyrrole synthesis, the Hantzsch pyridine synthesis, and the Fischer and Reissert indole syntheses. We did not mention that the synthesis of furans from 1,4-dicarbonyl compounds is known as the Feist-Benary synthesis, and there are many more like this. If you are really interested in these other names we suggest you consult a specialist book on heterocyclic chemistry. 

A method with considerable scope is a variation of the Feist-Benary synthesis using a 2-chloroaeyl chloride instead of a 2-chloroketone.105106 The main variation (Scheme 27) leads to acid 42 which can be epoxidized... 

Feist-Benary synthesis. Formation of furans from a-halogeno ketones or ethers and 1,3-dicarbo-nyl compounds in the presence of pyridine. With ammonia as condensing agent, pyrrole derivatives are always formed as secondary products. 

The Feist-Benary synthesis requires the presence of a base, e.g. aqueous Na2C03. It proceeds as a multistep reaction involving at least two intermediates (16/17) of which 3-hydroxy-2,3-dihydrofurans 17 can be isolated in some cases. The formation of 16 results from an aldol addition, that of 17 from an intramolecular nucleophilic substitution. Cyclic 1,3-diketones also react with a-halocarbonyl compounds according to the Feist-Benary synthesis to produce flirans, e.g. ... 

What are the structures of the products A - D and their modes of formation Consult ref [34], compare with p 59 (Feist-Benary synthesis). 

In this modification of the Feist-Benary synthesis of furans (section 15.14.1.4), ammonia or a primary amine, is incorporated. The pyrrole is probably formed by initial interaction of ammonia (or a primary amine) with the / -ketoester, the resulting / -aminocrotonate then being alkylated by the halo-ketone or -aldehyde. ... 

Two classic furan syntheses were described in Chapter 4 an adaptation of the Paal-Knorr method (section 4.2.1) and the Feist-Benary synthesis (section 4.2.3), which starts with an alpha-haloketone and a beta-ketoester. Other ring-closing processes have been devised and are outlined elsewhere. It is of practical current importance to start syntheses with the readily available furfural (furan-2-carbaldehyde) or fiiran itself. The reason for this is that large-scale commercial syntheses of these compounds have been developed, and thus they are readily available and inexpensive. 

The Feist-Benary synthesis proceeds via an aldol reaction followed by intramolecular O-alkylation and dehydration to yield the fiiran product as... 

J. Prakt. Chem. 332, 143 (1990) A. W. Trautwein etal., Bioorg. Med. Chem. Lett. 8,2381 (1998). Cf. Feist-Benary Synthesis Knorr Pyrrole Synthesis Paal-Knorr Pyrrole Synthesis. 

Cyclic 1,3-diketones also react with a-halocarbonyl compounds according to the Feist-Benary synthesis to produce frirans, for example ... 

Feist-Benary synthesis (furan) 72 Fiesselmann synthesis... 

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