Betaines and Other Unusual Structures

Heterocyclic analogs of ferrocene and macroheterocycles containing ferrocene fragments 90JOM93. 

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These cover the following topics (a) theoretical methods, with emphasis on the utility of such methods b) molecular dimensions, as determined by X-ray, electron diffraction and microwave spectra (c) molecular spectra, covering NMR, IR, UV, mass and photoelectron spectra [d) thermodynamic aspects, such as stability, ring strain, aromaticity, shape and conformation of saturated and partially saturated rings (c) tautomerism, including prototopic and ring-chain (/) betaine and other unusual structures. 

Heterocyclic betaines and other unusual structures have been the subject of extensive investigation [88AHC(44)269 92AHC32]. The specific focus of this report is to survey recent progress in the chemistry of heterocyclic betaines and molecules with a betaine character of general type 1 (Scheme 1), and should serve to complement other reviews that deal with heterocyclic betaines of alternant hydrocarbons [80AHC(26)1] and heterocyclic mesomeric betaines (85T2239). 

Structure and Stereochemistry (it is self-subdivided into Theoretical Aspects, Stereochemical Aspects, Betaines and Other Unusual Structures, Miscellaneous Substituted Heterocycles). 

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