Heterocycles rearrangement

The thermal acid- or base-catalyzed interconversion of 5-amino-l-phenyltriazoles (413) and 5-anilinotriazoles (415) was discovered by Dimroth. It is an example of a general class of heterocyclic rearrangements (416 417) now known by the name Dimroth rearrange-... 

However, depending on the nature of the initial heterocycle, rearrangements are possible. Alkylation of thiazole to form the thiazolium salt (390) and generation of the ylide (391) with triethylamine in the presence of DMAD gave not (392) but the isomeric product (393) by the rearrangement indicated (76JOC187). Rearrangements of these types are described in Chapters 4.07 and 4.19. 

Table 5 Heterocyclic Rearrangements Involving Side Chains (Mononuclear Heterocyclic Rearrangements)...

The mononuclear heterocyclic rearrangement (MHR) of isoxazole-3-amidoxime 108 in the presence of a base and hydroxylamine with concomitant removal of the amide moiety affords furazan acetaldoxime 109 (Scheme 56) (91CHE651, 91KGS827). 

Nitroethylfurazan 143 has been synthesized by base-promoted mononuclear heterocyclic rearrangement (MHR) of oxime 142 (Scheme 82) (36G819,82G181). 

The role of substituents X on the mononuclear heterocyclic rearrangement (MHR) of 20 phenylhydrazones 54 of 3-benzoyl-5-phenyl-l,2,4-oxadiazole into the triazoles 55 (Equation 2) has been investigated, allowing the influence of X on the product distribution to be evaluated and first-order rate constants and Hammett correlations to be determined <1999T12885>. 

It was shown that furoxans can be transformed to 1,2,3-triazoles. Thus, 4-acetylamino-3-arylazo-l,2,5-oxadiazole 2-oxides undergo two successive (cascade) mononuclear heterocyclic rearrangements in an aqueous basic medium with the formation of 4-acetylamino-2-aryl-5-nitro-2/7-l,2,3-triazoles (Equation 12) <2001MC230>, or 3,3 -disubsti-tuted 4,4 -azo-l,2,5-oxadiazole 2-oxides were found to undergo a rearrangement into 2-(furoxan-4-yl)-4-nitro-2//-1,2,3-triazole 1-oxides on heating in pertrifluoroacetic or peracetic acids (Equation 13) <2003MC272>. 

The thermal, acid- or base-catalyzed interconversion of 5-amino-1-phenyltriazoles and 5-anilinotriazoles was first observed by Dimroth. This has since been recognized as an example of a more general heterocyclic rearrangement (Scheme 53), where X and Y are hetero atoms carrying... 

M. Ruccia, N. Viviona u. D. Spinelli, Mononuclear Heterocyclic Rearrangements, in Advances in Heterocyclic Chemistry, Vol. 29, S. 141 169, Academic Press, Inc., New York San Francisco London 1981. 

A. R. Katritzky u. M. F. Gordeev, Heterocyclic Rearrangements of Benzofuroxans and Related Compounds, Heterocycles 35, 483 (1993) (Boulton-Katritzky-Umlagerung). 

Mononuclear Heterocyclic Rearrangements M. Ruccia, N. Vivona and D. Spinelli, Adv. Heterocycl. Chem., 1981, 29, 141-170. 

Meso-ionic compounds, 19, 1 Metal catalysts, action on pyridines, 2, 179 Monoazaindoles, 9, 27 Monocyclic pyrroles, oxidation, of, 15, 67 Monocyclic sullur-conlaining pyrones, 8, 219 Mononuclear heterocyclic rearrangements, 29, 141... 

Heterocyclic rearrangement. Suitable heterocycles can rearrange to 2-azetidi-nones. 

Ruccia, M., Vivona, N., Spinelli, D., Mononuclear Heterocyclic Rearrangements, 29, 141. 

Heterocyclic rearrangements initiated by nucleophilic addition to carbonyl... 

Pace, A., Buscemi, S. and Vivona, N. (2005) Heterocyclic rearrangements in constrained media. A Zeolite-directed photorearrangement of 1,2,4-oxadiazoles. Journal of Organic Chemistry, 70 (6), 2322-2324. 

Various l-aryl(hetaryl)-4-nitro-l,2,3-triazoles are obtained in result of heterocyclic rearrangements of uncondenced furoxans with the use of ionic liquids as reaction media [559-564],... 

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