Buchner ring expansion

Reaction of a phenyl ring with diazoacetic esters to give cyclohepta-2,4,6-trienecarboxylic acid esters. Intramolecular Buchner reaction is more useful in synthesis. Cf. Pfau-Platter azulene synthesis. 

Example 3, An intramolecular Buchner reaction within the Grubbs catalyst  

Name Reactions, 4 h ed., DOI 10.1007/978-3-642-01053-8 39, Springer-Verlag Berlin Heidelberg 2009 

Name Reactions A Collection of Detailed Mechanisms and Synthetic Applications, DOI 10.1007/978-3-319-03979-4 44, Springer International Publishing Switzerland 2014 

Buchner, E. Ber. 1896, 29, 106-109. Eduard Buchner (1860-1917) won Nobel Prize in 1907 for his work on fermentation. His name is imortalized with the Buchner funnels that we still use daily in organic laboratories. von E. Doering, W. Knox, L. H. J. Am. Chem. Soc. 1957, 79, 352-356. 

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Besides the general application in synthesis of cycloheptatrienes, different bicyclic products—for example, 0-tetralones and azulenones—can be prepared via the intramolecular Buchner ring expansion. 

Other references related to the Buchner ring expansion are cited in the literature. 

This reaction is related to the Buchner Ring Expansion. 

The a-(phenylsulfonyl)- and a-(ethoxyphosphoryl)-diazoacetamides 84d/e are exclusively converted to formal aromatic C-H insertion products 86d/e upon rhodium(II) perfluorobutyramide (Rh2(pfb)2> catalysis. The unsubstituted diazoacetamide 84a affords exclusively the Buchner ring expansion product 85a, and the Buchner reaction remains the favorable pathway with diazo substrates 84b/c, which bear relatively small a-substituents. The predominant formation of the Buchner products in these cases can be rationalized on the basis of steric effects. Various isoquinolinones are synthesized intramolecularly via six-membered ring formation with high regioelectivity and diastereoselectivity, while averting the common Buchner reaction. 

The dirhodium tetra(triphenylacetate) (Rh2TPA4)-catalyzed decomposition of ethyl 2-diazo-3-phenylpropanoate in the presence of aryl alkynes yields the angularly substituted dihydroazulenes 115. The formation of 115 presumably takes place by a tandem alkyne insertion/Buchner ring expansion pathway via intermediates 112-114. The reactivity of aryl alkynes with 2-diazo-3-phenylpropanoate is altered dramatically by changing the catalyst from dirhodium tetra(triphenylacetate) to dirhodium tetrapivalate (Rh2Piv4) cyclopropenes 116 are formed in 40-75% yields. 

Azulene formation from indanes and diazoacetates. Cf. Buchner ring expansion. 

In electrocyclizations that involve the participation of three-membered rings, the equilibrium favors the ring-opened species. The venerable Buchner ring expansion provides an apt example. A key step in Mander and co-workers har-ringtonolide synthesis involves a Buchner ring expansion of an aryl ring to a cycloheptatriene (Scheme 19.45). ... 

Ultimately it was found that by conducting the reaction with benzene in CH2C12 or in neat benzene, the ring expansion product 30a, via the norcaradiene 29a (Buchner reaction), was obtained in good yield (Scheme 8.5).17 Evaluation of the substrate... 

Buchner method of ring expansion Thermal or photochemical reaction of ethyl diazoacetate with benzenes and its homologs to give the isomeric esters of cycloheptatriene carboxylic acid. 68... 

Related reactions Buchner method of ring expansion ... 

Schiff bases s. Azomethines Schlotterbeck s. Buchner Schmidt reaction 17, 524 —, amines from carboxylic acids 19, 305 20, 366 —, lactams from ketones, cyclic, ring expansion... 

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