Dithiines

Dimethipin. 2,3-Dihydro-5,6-dimethyl-l,4-dithiin-l,l,4,4-tetraoxide [55290-64-7] (dimethipin, oxidimetbiin, UBI-N252, Harvard) (25) is used as a cotton defoHant and has been used as an experimental desiccant in potato vines. In addition, it defoHates nursery stock, grapes, dry beans, and natural mbber and is used as a desiccant for seed of canola, flax (l lnum usitatlssimum), rice, and sunflower (He/lanthus annuus) (10). The product has been available since the mid-1970s and the experimental work was first reported in 1974 (44). 

Oxidation of B Ahr s Salt with iodine or thionyl chloride gives tetracyano-l,4-dithiin [2448-55-7] (11), l,4-dithiin-2,3,5,6-tetracarbonitrile (62,63). The dithiin loses sulfur at 210°C to give tetracyanothiophene [4506-96-1] (12), 2,3,4,5-thio-phenetetracarbonitrile, and adds sulfur under the influence of sodium ethoxide to give the isothia2ole [4656-27-3] (13) (63). 

Dicyano-l,2-dithiete [53562-16-6] (14) is thought to be an intermediate when BAhr s Salt is oxidi2ed (64,65). If the oxidation is carried out in the presence of vinyl ethers, dihydro dithiins can be obtained in yields up to 60%. 

Diene moieties, reactive in [2 + 4] additions, can be formed from benzazetines by ring opening to azaxylylenes (Section 5.09.4.2.3). 3,4-Bis(trifluoromethyl)-l,2-dithietene is in equilibrium with hexafluorobutane-2,3-dithione, which adds alkenes to form 2,3-bis-(trifluoromethyl)-l,4-dithiins (Scheme 17 Section 5.15.2.4.6). Systems with more than two conjugated double bonds can react by [6ir + 2ir] processes, which in azepines can compete with the [47t + 27t] reaction (Scheme 18 Section 5.16.3.8.1). Oxepins prefer to react as 47t components, through their oxanorcaradiene isomer, in which the 47r-system is nearly planar (Section 5.17.2.2.5). Thiepins behave similarly (Section 5.17.2.4.4). Nonaromatic heteronins also react in orbital symmetry-controlled [4 + 2] and [8 + 2] cycloadditions (Scheme 19 Section 5.20.3.2.2). 

Dithiin, 2,4-dimethyl-2,4,6-triphenyl-thiophene synthesis from, 4, 903... 

Dithiin, tetraphenyl-dication salt, 3, 968 half-wave potential, 3, 968 synthesis, 3, 982... 

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