Thietanones

An interesting spiro compound (59) that contains the thietane ring was obtained in minor amounts by dimerization of dimethylketene and subsequent treatment with P2S5. Pyrolysis of the spiro structure produced 60 and the thietanethione 61, which can also be prepared by base-catalyzed rearrangement of 62, a process that can be carried out as well with 63 to give the 2-thietanone 60. The solvent and the basicity of the catalyst are important parameters in this rearrangement. 

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. ... 

Ring closure was observed by Johnson and Berchtold, who irradiated cyclic ) -ketosulfide 111 and terf-butyl alcohol with 253.7-nm light. A 2-thietanone derivatives was formed following intramolecular electron transfer from the sulfur atom to the excited carbonyl. An unstable dipolar... 

Studied by trapping the intermediates with silylating agents. The chlorination of 3,3-methylchloro-2-thietanone at — 20°C leads to the acyclic structure 210 from which the five-membered heterocycle 211 can be formed after treatment with hydrogen sulfide and cyclocondensation of the resulting thiole by elimination of HCl. Expulsion of CI2 leads to (212) (Eq. 52). 

The ring-opening reaction of 2-thietanone la by the action of benzylamine led to the formation of Ar-benzyl-3-mercapto-2-methylpropionamide in 60% yield (Equation 6) <2000MRC468>. 

The reaction of 3-iodopropionyl chloride with benzyltriethylammonium tetrathiomolybdate gave /3-thiolactone 77, but in rather poor yield (Equation 21) <1997T11835>. According to the authors, the poor yield resulted from the fact that 2-thietanones easily react with various nucleophilic reagents that are present in the reaction mixture and which result in cleavage of the S—C—O bond. 

These reactions, first described by Staudinger, have received little attention. A more recent investigation shows that the C -S bond of the thiones regioselectively adds across the C—C bond of the ketenes (equation 11) to form 2-thietanones (p-thiolactones). Primary adducts have been isolated only in a few cases. Most often they spontaneously decompose to yield an ene and COS (equation 12). 

Since it has been shown that this reaction generally gives 2-thietanones ( 3-thio-lactones), reports of 3-thietanones being formed should be treated skeptically (See Section XIII.3.B.). The chemical reactions and mass spectrum of the adduct of hexafluorothioacetone with diphenylketene have been interpreted on the basis of a 3-thietanone. ... 

Methylene derivatives of thietanes have been obtained by the Wittig reaction of 3-thietanones, as in the preparation of 365 and the phosphonium ylide 345 with p-nitrobenzaldehyde (to give 354). A Wittig reaction also has been applied to a 2-thietanone. ... 

Tetramethyl-3-thietanone 1-oxide 400 is obtained in 69% yield by oxidation of the thietane with peracetic acid in benzene. Amides of 3-thietanone-2,4-dicarboxylic acid 1-oxide are said to be obtained by treatment of amides of acetone dicarboxylic acid with thionyl chloride and 3-thietanone-l-oxides may be intermediate in the reaction of ketones with thionyl chloride. The -oxide of 3,3,4,4-tetraphenyl-2-thietanone may be an intermediate in the oxidation of the thietanone by nz-chloroperbenzoic acid, which is discussed in Section XIII.4.E. ... 

Thietanone 1,1-dioxides are unknown, although the tetraphenyl compound may be an intermediate in the oxidation of the 2-thietanone 308 with m-chloro-perbenzoic acid to the sulfinic-carboxylic acid anhydride 331. The methods discussed below apply to 3-thietanone 1,1-dioxides and derivatives. 

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