From Thiirans

R = Me) in acetonitrile, presumably by way of the episulphonium salts (297), to afford AW-dimethylthiazolidinium chloride (298) nearly quantitatively. In a parallel route to the same compounds, jS-chloroethylmercaptan (299) replaces the thiiran. The thiazolidinium salts are convertible into the stable cyclic sulphones (300) by peracetic acid. 

The use of styryl sulphide (301) similarly yields the expected 3,3-dimethyl-4-phenylthiazolidinium chloride (302 85%) its 5-phenyl isomer (303), 

A-Thiazines by Ring Contraction. See syntheses from aziridines, above. 

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A dramatic decrease in the magnitude of the magnetic susceptibility anisotropy is observed on going from thiirane to the open-chain analog, dimethyl sulfide, and has been attributed to non-local or ring-current effects (70JCP(52)5291). The decrease also is observed to a somewhat lesser extent in oxirane relative to dimethyl ether. 

Thiirane is more bactericidal than oxirane, and derivatives of 2-mei captomethylthiirane inhibit tuberculosis. The following pharmacological uses have been reported for compounds derived from thiirane derivatives gold complexes of the adducts of diethylphosphine and thiirane (antiarthritic), adducts of thiiranes and malononitrile (antibacterial, blood vessel dilators, muscle relaxants, sedatives), thermolysis products of thiirane 1-oxides and adducts of thiirane 1-oxides with sulfenyl chlorides (antibacterial), adducts of 2,3-diarylthiirene 1,1-dioxides with ynamines (antibacterial, parasiticidal), adducts of 2,3-diarylthiirene 1,1-dioxides with enamines (antifertility), adducts of p-aminophenylacetic esters with thiirane (immunosuppressants), adducts of amines and thiiranes (radioprotective drugs). 

Tliiobenzophenone 5-sulfide (35) was successfully generated by a cycloreversion of the 1,2,4-trithiolane 36 at 60°C or by a sulfur transfer from thiiranes to tliiobenzophenone (87JA902 97T939).Tlie thioketone 5-sulfide... 

The formation of alkenes from thiirane dioxides may not be stereospecifically controlled in the presence of a sufficiently strong base and sufficiently acidic protons in the three-membered ring. Under such conditions (essentially those typical for the Ramberg Backlund reaction), epimerization via a carbanion intermediate produces an equilibrium mixture of thiirane dioxides19,99 and consequently a mixture of cis- and trans-alkenes. 

The elimination of sulfur dioxide from thiirane dioxides leading to the corresponding alkenes is not the only result of base-induced reactions other products are also formed. This fact raises the question of the mechanistic pathway of this reaction. In general, the thiirane dioxide is treated with a large excess of the base in an appropriate solvent for several hours at room temperature or below. Bases commonly used are 2n NaOH (in water), NaOCH3 (in methanol), t-BuO-K + (in f-BuOH) and BuLi (in tetrahydrofuran) or KOH-CCU (in t-BuOH)16-19"112 113. 

Pyrolysis of the parent thiirane oxide 16a monitored by microwave spectroscopy led to the conclusion that the sulfur monoxide is generated in its triplet ground state, although the singlet state ( A) cannot be excluded completely (equation 8). A later study presented evidence, based on the stereoselective addition to dienes of sulfur monoxide generated from thiirane oxide as well as thermochemical data, that the ground state S is formed exclusively ° . ... 

A reaction of this type would resemble the well known thermal extrusion of sulfur monoxide from thiirane oxides ... 

Extrusion (or elimination) of sulfur from thiiranes and thiirenes is a facile process. Virtually all thiiranes and thiirenes, as well as their oxides and dioxides, undergo thermal extrusion of the sulfur moiety with increasing facility according to the trend S < < SO < S02. The thermolytic desulfurization mechanism is more complex than a simple cheletropic extrusion (85TL2789). 

Barton and coworkers exploited this strategy in the preparation of overcrowded ethylenes456 usually the desulfurization of a thiirane is accomplished by one equivalent of tertiary phosphine, mainly triphenylphosphine. However, spontaneous loss of sulfur from thiiranes substituted by aryl or halogen has sporadically been reported. Huisgen has reviewed this subject455 and performed many kinetic studies. He found that the desulfurization step can be accomplished by catalytic thiolates and also by thiobenzophenone or other thioketones, although in this case the reaction is slower (equation 131). 

A number of papers describe the synthesis of thietane rings starting from thiirane rings. Lucchini et al. studied the different reactivities of cis and trans di-fert-butylthiiranium ions, 96a and 96b, with water <1997JOC7018>. It was demonstrated that the reaction of cis di-fert-butylthiiranium ion 96a with water led first to the formation of an open-chain alcohol 97, which, after ring closure, formed the trans di-/r y-butylthiiranium ion 96b. The trans Ai-tert-butylthiiranium ion 96b then rearranged to the thietanium ion 98 (Equation 31). 

The kinetics and mechanism of rhenium-catalyzed desulfurization of thiiranes was studied experimentally and by means of computation <2006IC5351>. The oxorhenium dimer MeReO(edt)2 (X), where edt= 1,2-ethanedithiolate, was found to catalyze the transfer of S from thiiranes to triarylphosphines and triarylarsines. In the case of phosphines, catalysis was less effective because they converted the dimer catalyst rapidly to MeReO(edt)PAr3, a less effective catalyst. The rate law for AsArs, which did not transform the catalyst, was v = [thiirane][X] with k = 5.581 mol s at 25°C in CDCI3, for X = cyclohexene sulfide. The value of was 10.0 0.9kcalmoP, while AY was —21 3calK moP. The proposed mechanism is shown in Scheme 6. 

Geng etal. used DFT to examine abstraction of sulfur from thiirane by alkylidene carbenes <2005HX1402>. The greater the electronegativity of the carbene substituents (XYC=C), the lower the activation energy for abstraction. Electronic factors were found to be much more important than steric factors. 

Apeloig and Sklenak used high-level ab initio computation (QCISD/6-31G ) to determine the mechanism of a sulfur-transfer reaction between silylene (H2Si ) and thiirane <2000CJC1496>. A complex 41, formed in the first step over a barrier of 7.4kcalmol , was predicted to be observable in a matrix because the barrier to subsequent abstraction of S in a single step is higher at 14.9 kcal moP (Scheme 7). Other studies of abstraction of sulfur from thiirane by carbenes are discussed under Section 1.05.6.3.2. 

In this reaction, 2 equiv of thiirane is consumed in the formation of each disulfide group. One equivalent of alkene is also formed. The proposed mechanism of formation of cyclic disulfides from thiirane is shown in Scheme 31. 

Table 6 Synthesis of vinyl sulfones 197 from thiirane 1,1 -dioxides...

The reactions of thiiranes with alcohols, water, or acetic acid, in the presence of equimolar amounts of cerium(iv) trifluoromethanesulfonate, led to corresponding disulfides in 75-90% yield. When the reaction was carried out without nucleophiles in carbon tetrachloride, only the cyclic disulfide was formed (Equation (37) Table 7) <1998SC347>. A radical cation from thiirane and Ce(iv) is formed first. It attacks a molecule of solvent and the resultant radical dimerizes to form the disulfide. 

During polymerization of (R3 )-2-(phenoxymethyl)thiirane by diethylzinc/L-amino acid, the S-enantiomer of the thiirane was consumed preferentially <2002PSA3443>. Synthesis of optically active polymers prepared from thiiranes was described <2005TA2149>. 

Thiirane A-oxides are effective precursors for sulfur monoxide (SO) under thermal conditions <1997JOC8366>. The sulfur monoxide has been trapped by a variety of dienes to form cyclic sulfoxides. Extmsion of SO2 from thiirane A,A-dioxides to form alkenes under thermal conditions is well known. The reaction takes place readily at room temperature in the presence of KO/-Bu in tetrahydrofuran (THF). It constitutes the final step of the Ramberg-Backlund rearrangement <20030R357, 1999CC217>. 

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