Small-ring Compounds

Some small-ring compounds containing geminal fluorines suffer hydrolysis of fluorine only after initial opening of the ring For example, alkaline hydrolysis of... 

A. Goti, E. M. Corolero, and A. Brand, in Small Ring Compounds in Or-ganie Synthesis. V (A. deMeijere, ed.) [Topies in Current Chemistry, Vol. 178], p. 1. Springer-Verlag, Berlin, 1996. 

TABLE 4.5 Some Strained Small-Ring Compounds... 

Small ring compounds represent a fair portion of strained organic systems in which the geometry of sp and that of sp carbons have been distorted from the ideal configurations. Foremost among these reactive molecules are the small ring heterocycles, such as thiirane and thiirene oxides and dioxides. ... 

There appear to be three types of product, a low molecular weight product appearing to be small ring compounds (PI), an intermediate product (PII), and the usually desired high molecular weight polymer (PHI). Previous studies have concentrated only on PHI,... 

Selective Transformations of Small Ring Compounds in Redox Reactions... 

Ten years have passed since the first volume on "Small Ring Compounds in Organic Synthesis" was published within the series Topics in Current Chemistry (Vol. 133), and three more volumes have appeared in the meantime (Vol. 135, 144, 155). Wouldn t that be enough ... 

The two articles in this current volume describe recent developments with small ring compounds which have not teen compiled in such a context before. T. Hirao discusses selective transformations initiated by transition derivatives in the construction of functionally substituted five-, six- and seven-membered rings as well as open-chair compounds. Cycloadditions onto methylene- and alkylidene-cyclopropane derivatives, described by A. Goti, F. M. Cordero and A. Brandi, not only yield products with spirocyclopropane moieties which can be desirable as such or as potential mimics of gem-dimethyl groupings, but also intermediates which can undergo further transformations with ring-opening of the cyclopropane units. 

The authors, the editor and the publisher of this and a few more forthcoming Topics on "Small Ring Compounds in Organic Synthesis" intend to provide a service to the research community and hope that these books will generate more and fresh interest in this fascinating chemistry. 

Reductive and oxidative transformations of small ring compounds form the basis of a variety of versatile synthetic methods which include functionalization and carbon skeleton construction. Redox mechanisms of organotransition metal compounds play an important role in inducing or catalyzing specific reactions. Another useful route in this area is based on one-electron redox reactions. The redox tautomerism of dialkyl phosphonate also contributes to the efficiency of the reductive transformation of small ring compounds. This review summarizes selective transformations which have a high potential for chemical synthesis. 

Redox reactions are considered as being able to provide versatile and efficient methods for bringing about ring transformations. Transition metal complexes in particular are able to induce or catalyze oxidative or reductive transformations of small ring compounds. Organometallics, such as metal-lacycles derived by the insertion of metal atoms into rings, are involved as key intermediates in many cases, allowing subsequent functionalization or carbon-carbon bond formation. 

This review surveys recent developments in the selective transformation of small ring compounds via redox reactions, which furnish a variety of valuable methods of synthesis. 

Radicals are versatile synthetic intermediates. One of the efficient procedures for radical generation is based on one-electron oxidation or reduction with transition metal compounds. An important feature is that the redox activity of transition metal compounds can be controlled by appropriate ligands, in order to attain chemoselectivity in the generation of radicals. The application to small ring compounds provides useful methods for organic syntheses. Reductive transformation are first reviewed here. 

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