Thiirane, 2,3-diphenyl

The UV spectra of thiirane 1-oxide and (15,25)-(+)-2-methylthiirane 1-oxide show a broad maximum at about 205 nm (e —23 000). The latter shows a positive Cotton effect at low energy followed by a negative effect at high energy. The lowest excited states of thiirane 1-oxide involve excitations from the two lone pairs of the oxygen atom (79G19). 2,3-Diphenylthiirene 1-oxide and 1,1-dioxide show absorption due to the 1,2-diphenyl-ethylene chromophore. 

Wahrend Phenyl-thiiran bei entsprechender Behandlung in 1 -Phenyl-athandithiol-( 1,2) (65% d.Th.) iibergeht, ergibt rrans-l,2-Diphenyl-thiiran trans-1,2-Diphenyl-athylen. Bei Reduktionen von Thiiranen mit komplexen Metallhydriden behalten die gebildeten Olefine die Konfiguration des Ausgangsmaterials bei. 

Heating cyclic mono-, di- or tri-thiocarbonates, usually in the presence of base, gives thiiranes and carbon dioxide, carbon oxysulfide or carbon disulfide respectively. The methiodide salts of 2-methylimino-l,3-oxathiolanes are converted to thiiranes with high stereoselectivity, except for 5-aryl-substituted oxathiolanes (Scheme 146) (80LA1779). Flash vacuum thermolysis of l,3-oxathiolan-5-ones causes loss of carbon dioxide and nearly quantitative formation of thiiranes of inverted configuration (Scheme 147) (80JA744). For example, thermolysis of c/s-2,4-diphenyl-1,3-oxathiolan-5-one gives trans-2,4-diphenyl-thiirane. 

Three-membered rings should in principle be accessible by reaction of heteroaldehyde and -ketone complexes with Q sources. This was verified by the synthesis of the thiirane complex 143 from thiobenzaldehyde complex 99a and diphenyl diazomethane [Eq. (30)]. The reaction was assumed to proceed via a 1,3,4-thiadiazolidine complex as the intermediate that loses dinitrogen to give 143.254... 

Methylsulfanyl)-3,3-diphenyl-2-(trifluoromethyl)thiirane (4) Typical Procedure ... 

Methyl 3,3-Diphenyl-2-(trifluoromethyl)thiirane-2-carboxylate (13) Single Procedure ... 

Reaction of 2,7-diphenyl-5//,6//,7//-imidazole[2,l-/ ]-l,4-thiazolium-3-thiolate 380 with aromatic aldehydes in toluene give thiiranes 381 (Scheme 109) <2001CEJ3033>. The yields of thiiranes are collected in Table 22. 

The formation of 122 from 2,5-dihydrothiophene via the corresponding epoxide is not possible because of the easy oxidation of the sulfur atom. However, the analogous transformation of the sulfone has been reported to occur without difficulties. The reaction of oxirane 124 with thiirane 125 by treatment with Ph3PS and TFA at 70-80 °C was achieved (Scheme 65) <1983CHE1287>. With the same method, 3,3-diphenyl-3-sila-6-thiabicyclo[3.1.0]hexane 127 and the corresponding 3-germa derivative 129 are also accessible <1987JOM(327)C25>. 

Thiete structures have been suggested as fragmentation products in the mass spectra of a thietane fused to a 3-lactam, an ortho disulfide of a thiolbenzoate ester, -propanethiol, thiirane carboxylic acid esters, isothiazoles, thiazoles, 1,3-dithiole 2-thiones, 1,3-dithiolene-2-ones, S-ethyl thio-benzoate, and thianaphthene sulfones. Tetramethylthiete may have been formed on thermolysis of the p-toluenesulfonyl-hydrazone of 2,2,4,4-tetramethyl-3-thietanone. " Thiete 2-thione may be an intermediate in the decomposition of 1,2-ditholium salts by the action of bases. " 2,2-Diphenyl-2H-thiete is suggested as an intermediate in the reaction of diphenyldiazomethane with 1,2,3-benzo-thiadiazole which yields 9-phenylthioxanthene and three other products. ... 

The thermal desulfonylation of episulfones is highly stereospecific e.g., cis-2,3-dimethyl-thiirane-1,1-dioxide gives cw-2-butene , and trans- and cw-2,3-diphenyl thiirane 1,1-dioxides give trans and cis stilbenes, respectively . This result is remarkable in that the Woodward-Hoffman symmetry selection rules for inter-molecular cycloadditions (and their reversals) appear to exclude a concerted thermal decomposition of thiirane-l,l-dioxides . ... 

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