Bergmann reactions

The conversion of an ene-diyne 2.77 into a 1,4-benzenediyl diradical 2.78 on heating is known as the Bergmann reaction . The 1,4-aromatic radical 2.78 maybe converted into benzene or may react with CCI4 to givep-dichlorobenzene (2.79). Bergmann etal converted deuterium-labelled hexa-3-ene-l,5-diyne 2.80 on heating at 200°C into deuterium-labelled hexa-3-ene-l,5-diyne 2.81 in which both deuterium atoms were shifted from the terminal acylene positions to vinyl positions at the interior of the chain. 

Fig. 1.8 (a) Structural DNA-inactivating motives in radiomi-metic drugs (b) Bergmann reaction of dehydrobenzenes [119, 120]. 

Theoretical studies have been reported for various conformations for the Bergmann reaction of (3Z)-3-cycloundecene-l,5-diyne (Scheme 164). ... 

The Bergmann variation of the Balz Schiemann reaction is a two-step process featuring copper- or copper halide-catalyzed decomposition of aqueous or acetone solutions of arenediazonium fluoroborates containing alkyl or halogen substituents [30] A recent modification is a one-step technique featuring simultaneous diazoti-zation and decomposition by addition of aqueous sodium nitrite at 25 °C to a mixture of fluorobonc acid, copper powder, and 2 isopropyl 6 methylaniline to give 2-isopropyl-6 methylfluorobenzene in 73% yield [37]... 

The reviews by Rondestvedt (1960, 1976) are outdated so far as the mechanism of the Meerwein reaction is concerned. This statement is substantiated by Rondestvedt s own comment in his 1976 review (p. 226) in which he states that the generally accepted mechanism involves the aryl radical. .., though the manner of its formation and its subsequent reaction are still controversial . Meerwein et al., in their original paper (1939), expressed the opinion that the reaction is ionic in nature. A radical mechanism was first proposed by Koelsch in 1943 (see also Koelsch and Bockelheide, 1944). He received immediate support from Bergmann et al. (1944) and Bergmann and Weizmann (1944), in spite of the fact that Koelsch s claim was based on rather uncertain and vague arguments. 

Reimarm S, Hantke T, Roehr CC, Bergmann KE. Niggemann B Prevalence of adverse reactions to food in Germany - a population study. Allergy 2004 59 338-345. 

Arylalkenes can undergo various reactions when treated with sodium, since compounds such as a-methylstyrene are both olefins with allylic hydrogens and styrenes, both of which are reactive. The reaction of a-methylstyrene with sodium has been reported by Bergmann et al. (6i) to yield tetramers. More recent work by Kolobielski and Pines (56) has shown that dimers and products derived from dimers are formed when this compound is heated with a sodium-benzyl-sodium catalyst. Some of the major products were cumene (VII), p-terphenyl (VIII), and 1-methyl-1,3-diphenyl-cyclopentane (IX). 

The degradation is based upon a reaction first described by Bergmann and Miekeley and further developed by Abderhalden and Brockmann in which phenylisocyanate reacts with the a-amino group of the terminal amino acid of a peptide chain, yielding a phenylcarbamyl derivative. This can be cyclisized... 

An extensive review of the chemistry of aliphatic and aromatic azides is given by Boyer and Canter [167] and Gray [168]. Organic azides are subject to various reactions such as the Bergmann degradation and the synthesis of peptides, the well known Curtius rearrangement, the Darapsky synthesis of a-aminoacids [169], for synthesis of triazoles [170], tetrazoles ( Schmidt reaction ) [169] and [171] etc. These reactions lie beyond the scope of the present book. 

The thermal equilibrium among CBr20, CO, and Br2 was measured between 20 and 100°C by Schumacher and Bergmann.153 The CBr20 was photodecomposed between 10 and 40°C with a quantum efficiency of one by radiation below 3200 A. Foreign gases which do not absorb the radiation had no influence on the reaction. Also, neither Br nor excited Br2 initiated the decomposition. The mechanism is simply... 

BERGMANN AZLACTONE PEPTIDE SYNTHESIS. Conversion of an aoetylated amino add and an aldehyde into an azlactone with an alkylcnc side chain reaction with a second amino add with a second amino acid with mig opening and formation of an acylated unsaturated dipeptide, followed by catalytic hydrogenation and hydrolysis to the dipeptide. 

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