3- Thietanones, synthesis

Azibenzils 85 are effective reagents in the synthesis of 2-thietanones. With thiobenzophenone, elimination of nitrogen produces, via intramolecular cyclization, four- and five-membered ring isomers. ... 

The most effective synthesis for thietanones is the eliminative cyclization of halogenated ketones with hydrogen sulfide ions in the presence of bases (Eq. lOb). The reaction of 1,3-dibromoketone derivatives with sodium hydrogen sulfide produced 3-thietanones in association with a five-membered cyclic disulfide (Eq. 10c). 

Only a limited number of examples are known of applications of thietanes in organic synthesis. Prominent among these examples would be electrophilic ring opening reactions leading to polyfunctional sulfur compounds (33)-(37), utilization of 3-thietanones (55) and metal complexes (87) derived therefrom as oxyallyl zwitterion equivalents in cycloaddition reactions, synthesis of dipeptide (63) with a /3-thiolactone, Raney nickel desulfurization of thietanes (e.g. 120 cf. Table 7) as a route to gem-dimethyl compounds, and desulfurization of thietanes (e.g. 17) in the synthesis of cyclopropanes (also see Table 7). 

A synthesis of the functional core of the antibiotic leinamycin consisted of several steps, one of them being the preparation of an alkyl-substituted thietanone in moderate yield by cyclization of 2-mercapto propionic acid derivatives in isobutyl chloroformate and in the presence of triethylamine (Scheme 20) <2003T833, 2003PS1163>. 

The only naturally occurring 3-thietanones are found in the South African flowering plant, Berkheya barbata of the tribe Arctotideae. Structure 356 is representative of the compounds obtained from these plants, which are identified by spectroscopy and independent synthesis. The thietanone structure supplants an earlier structure that featured a five- instead of a four-membered ring. ... 

Thietanones also have been obtained by treatment of aliphatic ketones with an a-methylene group with thionyl chloride, usually in the presence of a base as shown for the synthesis of 359. A 3-thietanone was suggested as a possible structure for the product obtained by the acid-catalyzed hydrolysis of the bis-thioglycolic thioacetal of substituted benzaldehydes, but an elemental analysis was the only evidence. Treatment of l-diazo-3-phenylthio-2-propanone with acid gives the -phenyl salt of 3-thietanone (Section VII.1.). Similar 5-alkyl salts may be intermediates, but they readily decompose either by loss of the 5-alkyl group or... 

Thietanone 1,1-dioxides are intermediates in the synthesis of cyanine dyes used as photographic sensitizers. ... 

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