1.2- Oxathiin 2,2-dioxides

Treatment of 2,3-diphenylthiiren 1,1-dioxide with acyl-substituted sul-phonium ylides gives a thiet dioxide (123), an oxathiin dioxide (124), and a dithiin (125). An intermediate acyl thiiran 1,1-dioxide was suggested. The pyridinium ylide (126) gave 3-benzoyl-1,2-diphenylindolizine (127). ... 

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. 

Sultones react easily with amines and anilines <1989PHA294, 1989EJC259, 1987LA481> 1,2-oxathiin 2,2-dioxide derivatives 104 condensed to give the corresponding sultams 105 but 1,2-oxathiane 2,2-oxides 16 were cleaved by aniline or benzoylhydrazine derivatives to provide the corresponding sulfonic acids 106 (Scheme 25) <1993AFF256>. 

Similarly, using either sulfuric acid, the SOs/dioxane complex, or a solution of SO3 in chloroform/dioxane, 4,6-diphenyl-l,2-oxathiin 2,2-dioxide was obtained from phenyl acetylene <1999RJ0415>, 3,6-disubstituted-l,2-oxathiane 2,2-dioxides were obtained from allylphenol <2002RJ01210>, and 3,4-dihydro-6-phenyl-l,2-oxathiin-4-one 2,2-oxide was obtained from Ph-CO-CH2-COMe <1991CIL253>. 

Further, a 1,2-oxathiane 2,2-dioxide derivative was obtained as a by-product (15-25%) in the enantioselective synthesis of Oasomycin A <2007AG545> all efforts to suppress this side reaction were not successful, and the reaction products of the hexafluorobutadiene sulfotrioxidation (among the main products a 4,5-dihydro-l,2-oxathiin 2,2-dioxide derivative) were identified by F NMR spectroscopy <2007RJA424>. 

A series of 4,6-disubstituted-l,3-dihydrothieno[3,4- ]thiophene-2,2-dioxides (sulfolenes) 477-480 was obtained <2002JOC9267> from 5,7-disubstituted l,4-dihydrothieno[3,4-7l[2,3]oxathiin-3-oxides (thienosultines) 476a-d by heating in benzene in sealed tube (Equation 15). 

Similar transformations are based upon 1,2-oxathiin 2,2-dioxides (8-sultones), which can be converted subsequently into furans (51RTC35), thiophenes (60LA(630)l2o) (Scheme 68) or pyrroles (61LA(646)32). 

The pyridazine dioxide derivative (108) was made by intramolecular nitroso compound dimerization as shown (Scheme 23). 1,2-Oxathiin 2,2-dioxides are obtained by the addition of sulfuric acid to a,(3-unsaturated ketones, e.g. (109) — (110) (66HC(21-2)774). 1,2-Dithiins are synthesized from conjugated diynes using benzyl thiol reductive debenzylation of intermediate (111) by sodium in liquid ammonia at - 70°C gives, after aerial oxidation, the 1,2-dithiin (112) (67AG(E)698). 

Chemical shifts of protons of 1,2-dithiin (Table 4) show no evidence of a ring current, but borderline aromaticity of a 1,2-oxathiin 2,2-dioxide derivative has been inferred from the chemical shift of H-6 which falls midway between that for a proton in a nonaromatic cyclic ether and for H-2 of furan (64JOC1110). 13C shifts of 1,2-oxathiin 2,2-dioxides at the C-4 and C-6 positions have been considered anomalous but may be rationalized by invoking mesomeric withdrawal of electron density from these positions by the SO2 moiety (770MR(10)208>. 

In the 1,2-series, there are some conflicting reports concerning the extrusion of sulfur dioxide from 1,2-oxathiin 2,2-dioxides. In some instances the reaction proceeds smoothly to afford the corresponding furan, whereas in others pyrolysis merely produces an intractable... 

Desulfurization reactions in the 1,2-series are encountered among derivatives of both oxathiins and dithiins. 1,2-Oxathiin 2,2-dioxides extrude sulfur dioxide at elevated temperature over zinc oxide, iron or copper oxide to give the corresponding furan (66HC(21 -2)789) [cf. Section 2.26.3.1.2). Copper is a good catalyst for the extrusion of sulfur and sulfur dioxide from dibenzo[c,e3[l,2]dithiin (40) and its dioxide respectively to give dibenzothiophene (66HC(21-2)968). 

The sulfonyl group is a key feature in the preparation of the unusually substituted dithiin sulfone (174) from dibenzyl sulfone. The acidic a-protons are abstracted with sodium hydride and the carbanionic intermediates react with carbon disulfide. The reaction is quenched with methyl iodide to give (174) in 17% yield (73BSF637). Another multisubstituted dithiin (175) is available from the reaction of diphenylthiirene dioxide with the ylide (176) (Scheme 21) but again the yield is low. However, the reaction is of particular interest in so far as the product mixture also contains a derivative of the rare oxathiin nucleus. Indeed of the three products isolated the oxathiin sulfone (177) is formed in marginally the highest yield (73BCJ667). 

Various dihydro-1,4-oxathiins and dihydro-1,4-dithiins are reported to be useful in areas other than agriculture. Thus, 2,3-dihydro-l,4-dithiin-5,6-dicarboximides display a wide spectrum of biological activity (77SST(4)332) while derivatives of the basic structure (243) have been patented as tranquilizers, anticonvulsants and hypnotics (76GEP2550163). Sedative, myorelaxant and cataleptic properties are associated with certain 2,1-benzoxathiane 2,2-dioxides (75BRP1383459). 

Oxathiin 2,2-dioxides (sultones) (e.g., 150) are obtained by the addition of sulfur trioxide to dienes or by ringclosing metathesis (RCM) of sulfonates using the second-generation Grubbs ruthenium catalyst (Scheme 75) . The same catalyst was also successfully employed in the RCM of diallyl disulfide 151 which led quantitatively to 3,6-dihydro-l,2-dithiin 152 (Scheme 76) <20020L1767>. 

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