Heterocycles containing One Sulphur Atom

Heterocycles containing One Sulphur Atom Thiopyrans. - A convenient synthesis of 2-phenylthiopyran-4-one (217) has been developed from methyl styryl ketone and ethyl formate. The enolate... 

Other work on four-membered heterocycles containing one sulphur atom includes a study of the vacuum-u.v. photodecomposition of thietan 1,1-dioxide and the formation of a thietanone from a xanthate and diphenylketen, and reports of several thiets. There is evidence that photolysis of (107) in a matrix at 77 K leads to the o-thiobenzoquinone (108), which is interconvertible with the... 

Fused Heterocycles containing One Oxygen or Sulphur Atom... 

Monocyclic heterocycles containing three to ten members, and one or more hetero-atoms, are named systematically by using a prefix or prefixes to indicate the nature of the hetero-atoms as presented in the following table. For example, t/iiacyclobutane contains the hetero-atom sulphur (S). 

Isoxazole, pyrazole and isothiazole constitute the 1,2-azole family of heterocycles that contain two hetero-atoms, one of which is a nitrogen atom. The second hetero-atom is oxygen, nitrogen or sulphur, respectively. 

The reaction of sulphides with (dichloroiodo)benzene can lead to several kinds of products depending on the substrate and the reaction conditions [19]. Sulphides of great structural diversity (aliphatic, aromatic, heterocyclic) were oxidized efficiently by (dichloroiodo)benzene (one equivalent) in aqueous pyridine. The reaction was almost instantaneous and not noticeably sensitive to steric or electronic effects. Ethylenic double bonds were not attacked under these conditions however, in vinylic sulphides containing an electron-withdrawing group (COOH or RSO) ft- to the sulphur atom the oxidation was accompanied by nucleophilic attack to the double bond resulting in a mixture of products. The method is suitable for the preparation of I80-labelled sulphoxides using small quantities of H2,80. 

As distinct from benzene and other ring systems which contain carbon as the only ring constituent are a number of heterocyclic ring compounds in which one or more of the carbons is replaced by an oxygen, nitrogen or sulphur atom. These too may be either saturated or unsaturated. 

Any ring system containing at least one heteroatom (i.e. an atom other than carbon - typically nitrogen, oxygen, or sulphur) can be described as heterocyclic. This broad definition encompasses both aromatic heterocycles (such as pyridine 5.1) and their non-aromatic counterparts (piperidine 1.7). 

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