Dithianes and trithianes

5 HETEROCYCLES CONTAINING TWO OR MORE SULFUR ATOMS 6.4.5.1 Dithianes and Trithianes 

A Newman-Kwart rearrangement features in a synthesis of 3,8-diiododibenzo-l,2-dithiin which possesses a screw-boat conformation. The substituents allow elaboration of the molecule, though preferably prior to formation of the thiin ring 06TL9135 . 

3-Dithiolanes and 1,3-oxathiolanes also undergo carbene insertion on treatment with methyl diazoacetate in the presence of Rh2(OAc)4, to give 1,4-dithiane-2-carboxylates and 

4-Dithiins are formed regioselectively and in high yield when fused pentathiepins 48 are treated with an electron deficient alkyne and PhjP at room temperature the stepwise loss of S atoms leading to an o-thioquinone is proposed 06OL4529 . 

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The molecular mechanics method314 has been applied to the calculation of conformational properties of the thiane, dithiane and trithiane oxide systems315, which are... 

Amino acid-based dithiazines 281 were lithiated and allowed to react with benzaldehyde, giving products 282 in good yields but with low diastereoselectivity (Scheme 72)451. These adducts underwent externally sensitizer photofragmentation with quantum efficiency comparable to the parent dithiane and trithiane adducts. 

The same preferences have been calculated315 and observed319 in the 1,2-dithiane oxide system. Although the chair forms are also more stable than the twist or boat in 1,3-, 1,4-dithianes and 1,3,5-trithianes, the preference of the oxygen is highly variable, depending on steric and electronic interactions. 

Calculations have also been performed for the monosulfoxides of 1,4-dithiane, 1,3-dithiane and 1,3,5-trithiane, the cis and trans disulfoxides of 1,4-dithiane and 1,3,5-trithiane and the cis and trans trisulfoxides of 1,3,5-trithiane (76T529). For all the compounds mentioned, a chair conformer is calculated to be most stable and the results are consistent with experimental findings which reveal that the S—O- bond exhibits an axial preference within 1,4-dithiane 1-oxide but an equatorial preference within 1,3-dithiane 1-oxide and 1,3,5-trithiane 1-oxide (Section 2.26.2.5). 

Lithio-l,3-dithiane and 2-lithio-l,3,5-trithiane have been transformed into 2-substituted benzylamines 273 and 274, respectively, by reaction with a mixture of benzaldehyde and lithium hexamethyl disilazide449. In the case of compound 266, the corresponding derivatives 275 and 276 have also been prepared. Related compounds were used for the preparation of photolabile molecular hosts. 

Tetravalent phosphoms groups prefer axial orientations in 1,3-dithianes and 1,3,5-trithianes. NMR studies have indicated a preference of about 1 kcal for the diphenylphosphoryl group. When combined with the conformational energy in a cyclohexane ring, this suggests an anomeric effect of around 3 kcal. ... 

A short remark on tri- and polythia compounds Several such substrates (1,3.5-trithiane, 1,4,7-trithiacyclononane, 1,4,7,10-tetrathiacyclodecane, and 1,5,8,12-tetrathiacyclotetradecane) have been subjected to one-electron oxidation. 17,122,131 xhe common feature of the optical absorptions attributable to the intramolecular radical cations derived from these compounds indicates that interaction occurs mainly between two of the sulfur atoms. For example, max = 600 and 610 nm for the radical cations from 1,3-dithiane and 1,3,5-trithiane, respectively. For the two transients derived from 2,5-dithiaheptane and 1,4,7-trithiacyclononane, respectively, even the same max = 525 nm has been measured. Some tailing on the low energy side and broadening of the absorption bands in the trithia systems suggests, however, some small additional influence by the other sulfurs on the electronic energy levels. This conclusion is fully in line with photoelectron spectroscopy data. 32... 

Dithiolans, 1,3-Dithians, 1,4-Dithians, and 1,3,5-Trithians.— Because of the significance of cyclic dithioacetals in organic synthesis, the efforts in investigating their chemical, physical, and structural properties are still increasing. Various di-, tri-, and tetra-alkyl-substituted 1,3-dithians have been prepared, and their... 

An interesting series of papers on the existence of an anomeric effect in electro-negatively substituted 1,3,5-trithians, 1,3-dithians, and thians has appeared. Thus, the copper(i)-catalysed decomposition of benzoyl t-butyl peroxide in the presence of 1,3,5-trithian in benzene gave a mixture of 2-benzoyloxy- and 2,4-di-benzoyloxy-l,3,5-trithian (96) and (97), respectively. The dibenzoyloxy-derivative (97), formed as the major product when a 3 1 ratio of peroxide to... 

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