27/-Benzo thietes

Oxygen and Sulphur-containing Heterocycles.—Dittmer and Nelsen have improved the yield of the known benzo[/>]thiete-1,1-dioxide (281) which was prepared in six steps from (280) thermolysis of (281) gave the sultine (282). Improved... 

The catalysed macrocyclization of thietanes by metal carbonyl complexes has been reviewed <00ACR171>. Electronically stabilized thiones have been shown to undergo [2+2] cycloaddition with benzyne to give 27/-benzo[i>]thietes, for example 6 <00BCJ155>. 

H-Benzo[6]thiete synthesis, 4, 824 Benzothietes ring opening, 7, 423 synthesis, 4, 824 Benzothietide anions stability, 7, 419 1H-1 A4-1 -Benzothiins pxidation, 4, 969 stability, 3, 926 structure, 3, 894 Benzothiins, dihydrodisproportionation, 3, 908 lH-2-Benzothiin, 3,4-dihydro-2,2-dioxide... 

The 8 + 2-cycloaddition of 2//-cy c I o h cpta[h ] furan -2 - one (155) with acyclic 1,3-dienes provides a facile route to bicyclo[5.3.0] ring systems (156) (Scheme 61).291 2H-Benzo[Z>]thiete in the o-quinoid form undergoes 8 + 2-cycloaddition with 1,3-dithiolane-2-thione, l,3-dithiole-2-thiones, and adamantanethione to produce 4//-1,3-benzoditliianes.292... 

Benzo[7]thiete 41 reacts in the ortho-qumoiA isomer 41 with cyclic trithiocarbonates such as l,3-dithiolane-2-thione, (ethylene trithiocarbonate), l,3-dithiole-2-thiones, and adamantanethione <1997LA1603>. In boiling toluene, 1,3 dithiolane and dithiole derivatives formed the spiro compound 42 and 43 in good yield. The related l,3-dithiole-2-thiones reacted chemoselectively at the C=S double bond. The use of adamantanethione yielded the polycyclic adduct 44 in a smooth and quantitative reaction (Scheme 3). 

The reactivity of the benzo analogue of compound 41, that is, 2//-naphtho[l,2-4]thiete 47, has also been studied. Cycloaddition reactions with dienophiles or heterodienophiles performed in boiling toluene yielded naphtho-condensed sulfur heterocycles (Scheme 5) <1998JHC1505>. 

Benzyne generated at room temperature from phenyl[2-(trimethylsilyl)phenyl]iodonium trifluoromethanesulfo-nate has been trapped in a [4+2] cycloaddition reaction with diarylthiones. The initial product, a 6-aryl-477 dibenzo[, r/]thiopyran, is accompanied by 6-aryl-67/-dibenzo[, r/]thiopyran arising by 1,3-prototropic aromatization of the cycloadduct (Equation 114). The use of sterically congested thiones, such as thiopivalophenones, results in competition from a [2+2] cycloaddition and 2/7-benzo[A]thietes are the sole products <2000BCJ155>. 

Benzo[3]thiete is a source of o-thioquinone methides, heterodienes which react with 1,4-naphthoquinones or 1,4-epoxynaphthalenes to give the benzo[ ]thioxanthene system. With the former reagents, the initial products undergo an autooxidation and 6,ll-dihydro-12//-benzo[7]thioxanthen-6,ll-diones result. The 6,11-epoxy adducts which are formed from the epoxynaphthalenes can be dehydrated to 12//-benzo[7]thioxanthenes or converted into the dihydrobenzothioxanthene-6-ol (Scheme 131) <1995JPR379>. 

The first thiete fused to an aromatic system 219 (and an anthracene derivative) was reported in 1965 and was prepared by reduction of a naphthothiete sulfone. An attempt to prepare benzothiete by desulfurization of benzo-l,2-dithiolane was unsuccessful. Photolysis of benzo-l,2-dithiolane 1,1-dioxide in an attempt to extrude sulfur dioxide to give benzothiete also was unsuccessful. The naphthothiete 205, however, was prepared by extrusion of sulfur dioxide from 220 and nitrogen from 221. Thiete 205 also is obtained in 6-8% yield by treatment of 1,8-dehydronaphthalene with carbon disulfide. The unstable thiolactone 211 was formed by a photochemical extrusion of benzaldehyde from 222 and from 222a at 350°C. The benzothietes 209, 223, " and 224 have been... 

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. ... 

H-benzo[b] thiete 1,1-dioxide 269 has been obtained in a 19% overall yield from thietane 1,1-dioxide and thiete sulfone 270. Diels-Alder additions of... 

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