Dithietane Explained

Dithietanes are saturated heterocyclic compounds that contain two divalent sulfur atoms and two sp³-hybridized carbon centers.^{[1] [2]} Two isomers are possible for this class of organosulfur compounds:

1,2-Dithietanes

1,2-dithietanes, 4-membered rings where the two sulfur atoms are adjacent, are very rare. The first stable 1,2-dithietane to be reported was the dithiatopazine, formed by intramolecular photodimerization of a dithiocarbonyl compound.^[3] 1,2-Dithietanes are to be distinguished from 1,2-dithietes, containing two adjacent sulfur atoms and two sp²-hybridized carbon centers.

A stable 1,2-dithietane derivative is trans-3,4-diethyl-1,2-dithietane 1,1-dioxide, formed by the spontaneous dimerization of the lachrymatory agent syn-propanethial-S-oxide, found in onion.^[4]

1,3-Dithietanes

In 1,3-dithietanes, the sulfur atoms are non-adjacent.^[5] 1,3-Dithietane itself, a colorless, easily sublimed, crystalline, unpleasant-smelling solid with melting point 105-106 °C, was first prepared in 1976 by reaction of bis(chloromethyl) sulfoxide with sodium sulfide followed by THF-borane reduction of the first formed 1,3-dithietane 1-oxide, as shown in the scheme below.^{[6] [7]} Carbon-substituted 1,3-dithietanes are well known, with the first examples being described as early as 1872. Examples include 2,2,4,4-tetrachloro-1,3-dithietane, the photochemically-formed dimer of thiophosgene, and tetrakis(trifluoromethyl)-1,3-dithietane, [(CF₃)₂CS]₂.

Oxidized forms of 1,3-dithietane are well known, although they are often not prepared from the dithietane. Examples include the so-called zwiebelanes (2,3-dimethyl-5,6-dithiabicyclo[2.1.1]hexane S-oxides) from onion volatiles^[8] and 1,3-dithietane 1,1,3,3-tetraoxide, the so-called sulfene dimer.^[9]

Notes and References

1. Drabowicz . J . Lewkowski, J . Kudelska, W . Zając, A . Four-membered Rings with Two Sulfur Atoms . Comprehensive Heterocyclic Chemistry III . 2008 . 2 . 18 . 811–852 . 10.1016/B978-008044992-0.00218-2.
2. Zoller . U . Four-membered Rings with Two Sulfur Atoms . Comprehensive Heterocyclic Chemistry II . 1996 . 1 . 35 . 1113–1138 . 10.1016/B978-008096518-5.00035-6. 9780080965185 .
3. Nicolaou . KC . Hwang, CK . Duggan, ME . Carroll, PJ . Dithiatopazine. The first stable 1,2-dithietane . J. Am. Chem. Soc.. 1987. 109. 12. 3801–3802. 10.1021/ja00246a059.
4. Block . E . Bazzi, AA . Revelle, LK . The chemistry of sulfines. 6. Dimer of the onion lachrymatory factor: the first stable 1,2-dithietane derivative . J. Am. Chem. Soc.. 1980. 102. 7. 2490–2491. 10.1021/ja00527a074.
5. Luh . TY . Leung, MK. Product Subclass 2: 1,3-Dithietanes . Sci. Synth. . 2007 . 30 . 203–219.
6. Block . E . Corey, ER . Penn, RE . Renken, TL . Sherwin, PF . 1,3-Dithietane . J. Am. Chem. Soc.. 1976. 98. 18. 5715–5717. 10.1021/ja00434a061.
7. Block . E . Corey, ER . Penn, RE . Renken, TL . Sherwin, PF . Bock, H . Hirabayashi, T . Mohmand, S . Solouki, B . Synthesis and Thermal Decomposition of 1,3-Dithietane and its S-Oxides . J. Am. Chem. Soc.. 1982. 104. 11. 3119–3130. 10.1021/ja00375a030.
8. Block . E . Thiruvazhi, M . Toscano, PJ . Bayer, T . Grisoni, S . Zhao, SH . Allium Chemistry: Structure, Synthesis, Natural Occurrence in Onion (Allium cepa), and Reactions of 2,3-Dimethyl-5,6-dithiabicyclo[2.1.1]hexane S-Oxides . J. Am. Chem. Soc.. 1996. 118. 12. 2790–2798. 10.1021/ja951134t.
9. Opitz. G . Mohl, HR. Disulfene . Angew. Chem. Int. Ed.. 1969. 8. 1. 73. 10.1002/anie.196900731.