Oxathiins—

Oxathiins. - The sulphones (244) have been cyclized, in moderate yields, to the oxathiins (244a) by acetic anhydride-POCla- Tropone in mineral acid adds on 2-mercaptoethanol to give a mixture of the 1,4-oxathiins (245). Bicyclic lactones such as (246a) have been synthesized from the oxathiinone (246b thp = tetrahydropyranyl).  

Sindelar, J. Jilek, J. Koerbl, F. Jancik, E. Svatek, J. Metysova, and M. Protiva, Collect. Czech. Chem. Commun., 1980, 45, 3166. 

Tamura, C. Mukai, M. Ikeda, and M. Kido, Chem. Lett., 1981, 619. 

Cavazza, G. Morganti, A. Guerriero, and P. Francesco, J. Chem. Soc., Perkin Trans. J, 1981,1868. 

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Various 1,4-oxathiins have been converted to the sulfoxides in a highly stereoselective reaction. The sulfoxides undergo a thermal retro-Diels-Alder reaction to ot,a -dioxosulrines which can behave both as electron deficient dienes and as dienophiles, affording different oxathiins and dihydrothiopyran 1-oxides, respectively <96T12233>. In like manner, o-thioquinone 5-oxides have been generated and they too exhibit diene and dienophile behaviour <96T12247>. 

Oxathiins derived from the cyclic diacylthione (60) and glycals by a cycloaddition reaction yield glycosides on desulfurization, offering an alternative approach to glycosyl transfer <96AG(E)777>. 

Oxathiine derivatives lb 301,304 Oxathizine fungicides la 44 Oxazepam la 364 Oxazolidinthione derivatives lb 301 Oxeladine citrate lb 327 Oxidation, aluminium isopropoxide la 59 -, atmospheric oxygen la 60 -, chromic acid la 59, 60 -, hydrogen peroxide la 59 -, iodine la 60... 

The desulfurization pathway was proposed to be BT -> BT sulfone -> benzo[e][l,2]oxanthiin S-oxide -> o-hydroxystyrene. Additionally, formation of the intermediate benzo(e)(l,2)oxathiin S,S dioxide was inferred to a side pathway resulting in formation of benzofuran as shown in Fig. 7. This pathway is similar to that reported for Sinorhizobium KT55, Paenibacillus sp. strain All-2 and R. erythropolis KT462. 

Other heterocyclic systems prepared by a thionyl chloride reaction include fused thiazoles,71 thiatriazoles,72 oxathiins,73 and dithiins 74 some further examples are given in reviews.53... 

Langa et al. [67] described the microwave-induced Diels-Alder reaction of o-quino-dimethane, generated in situ from 4,5-benzo-3,6-dihydro-l,2-oxathiin-2-oxide (74) (sultine), [68, 69] leading to cycloadduct 75 (Scheme 9.21). This reaction was the first application of microwave irradiation to the preparation of a functionalized C60 [67]. 

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