Thietes oxidation

Dithietane oxides, Thietane oxides, Thiete oxides... 

F-(2,2,4,4-Tetrakis(trifluoromethyl)thietane is the only known example of per-fluorinated thietanes. It can be prepared by high-yield reaction of (CF3)2C=Cp2 with sulfur, catalyzed by CsF. First perfluorinated thiete was prepared by the reaction of hexafluorpropene trimer with (CH3)3CSH and later by dehydrofluorination of unsaturated thiol [(CF3)2CF]2C=C(SH)CF3 (X=H). The hydrolysis of sulfenul chloride [(CF3)2CF]2C=C(SC1)CF3 afforded perfluorinated thiete oxide. ... 

Thiets react with cyclopentadienylcobalt dicarbonyl to yield complexes of thioacroleins, which are valence tautomers of thiets. Oxidation of 3-ethyl-4-methylthiet and 3-propyl-4-ethylthiet with hydrogen peroxide in acetic anhydride did not give the S-oxides, but instead 2-ethylbut-2-enal and 2-propyl-pent-2-enal, respectively. ... 

Thiete sulfones may be74b converted to the corresponding saturated thietanes and followed by oxidation of the latter to the desired sulfoxides185 (equation 82). By chromatography, the mixture (207) can be separated to the cis and trans isomers. 

Meinwald and coworkers71 studied the chemistry of naphtho[l, 8-bc]thiete and its S-oxides. The reaction of the sulphone 2 with LAH (equation 29) is of particular and direct relevance to this section since it is different from the reductions that have been discussed thus far, because the major reaction pathway is now cleavage of an S—C bond, rather than a deoxygenation of the sulphur atom. The major product (equation 29) was isolated in 65% yield two minor products accounted for a further 15% yield. One of the minor products is 1-methylthionaphthalene and this was most probably produced by an initial reduction of the strained 1,8-naphthosulphone, 2, to the thiete, which was then cleaved to the thiol and subsequently methylated. Meinwald also showed71 that the thiete was subject to cleavage by LAH as well as that both molecules were susceptible to attack and cleavage by other nucleophiles, notably methyllithium. These reactions are in fact very useful in attempts to assess a probable mechanism for the reduction of sulphones by LAH and this will be discussed at the end of this section. 

Chiral thietane dioxides, synthesis of 449 Chiral thiete dioxides, synthesis of 449 Chlorine compounds, as oxidizing agents... 

The preparation and investigation of the thietane oxide system (5a) is largely associated with stereochemical and conformational studies . The investigation of the thietane dioxides (5b) is substantially related to the chemistry of sulfenes , the [2 -I- 2] cycloaddition of which with enamines is probably the method of choice for the synthesis of 5b . The study of the thiete dioxide system (6) evolved, at least in part, from the recognition that the unstable thiete system 183 can be uniquely stabilized when the sulfur in the system is transformed into the corresponding sulfone , and that the thiete dioxide system is very useful in cycloadditions and thermolytic reactions. The main interest in the dithietane oxides and dioxides (7) appears to lie in the synthetic challenge associated with their preparation, as well as in their unique structural features and chemical behavior under thermolytic conditions . ... 

A preparation of 3-substituted thiete dioxides takes advantage of the commercial availability of the parent four-membered thietanes. The latter is oxidized to the sulfone, which in turn is photochemically mono- or di-chlorinated in the 3-position. The 3-chlorothietane dioxide (239a) can be easily transformed into the thiete dioxide, whereas the 3,3-dichloro homolog is transformed into the 3-chloro-2H-thiete 1,1-dioxide (240b) (equation 91). 240b reacts with carbanions, amines, alcohols and thiols to give the corresponding 3-substituted thiete dioxides. ... 

Cycloadditions of nitrones, nitrile oxides or diazo compounds to thiete dioxides do not show the high stereoselectivity observed with acyclic vinyl sulfones, and mixtures of the two possible adducts are formed . The charge-transfer stabilization energy calculated according to the Klopman-Salem perturbational approach is able to account for the experimental trends of the isomer ratio in terms of the major stereochemical structural differences between the acyclic vinyl sulfones and the four-membered ring sulfones (see Section IV.B.3). 

The reaction of Af,Af-dimethyl-( )-styrylamine (73) with a halogen-substituted methanesulfonyl chloride allowed the first stereoselective formation of the halogenated thietane 1,1-dioxide 74, which then could be converted to the corresponding thiete sulfone 75 via a Cope elimination of the corresponding AT-oxide. ... 

Application of the enamine-sulfene cycloaddition allowed the synthesis of 78 and 79 from the corresponding a,/l-unsaturated amines and sulfenes. Similarly, using enamine 80, the crystalline morpholino thietane dioxides (81) were produced. Elimination via the N-oxide gave the corresponding thiete dioxide, whereas reduction by LiAlH4 yielded the thietane 82. 

Thietes can be prepared by elimination from appropriately substituted thietanes. 2,4-Diarylthiete 1,1-dioxides (146 and 147) were produced in good yields by peracid oxidation and intramolecular amine oxide elimination of 3-dimethylaminothietane 1,1-dioxides (Eq. 23). 

The oxides of thiete and benzothiete have been prepared from halogenated thietane oxides by elimination reactions. (Eqs. 25 and 26)... 

A limited amount of 170 NMR chemical shift data is available for thietane 1-oxides and 1,1-dioxides and thiete 1,1-dioxides. These data, summarized along with selected data for rings of other sizes in Table 4, indicate that there is once again a maximum in deshielding... 

Table 4 170 NMR Chemical Shifts for Thietane and Thiete S-Oxides and Related Compounds Compound Chemical shift (p.p.m.) Solvent/110 reference Ref.

Scheme 1 summarizes some of the common electron-impact induced fragmentation pathways available to thietanes, thietes and their 5-oxides. Major processes include retro-2 + 2 fragmentation for thietanes, thiolactones and iminothietanes, loss of sulfur oxides for thietane 5-oxides, and loss of an a-hydrogen atom from thietes and benzothietes. Certain of these processes, considered to involve electron-impact induced pathways, may actually involve thermolytic reactions occurring in the source region of the mass spectrometer (78JHC421,71JA676). 

Oxygen can be introduced into the a-positions of thietanes by treatment of the thietane with lead tetraacetate as in the formation of (204) (75JOC3046). Thietanones can be prepared by hydrolysis of thiete enamines such as (205) (65LA(684)103) or by oxidation of 3-thietanol with DMSO/benzoic anhydride (78PS(4)167>. Thietanones can be converted into various ring-substituted sulfur derivatives as already illustrated in reactions of (68) and preparation of (199). 

A4-Naphtho[l,8-6c]thiete 1-oxide 13C NMR, 7, 415 (76JA6643) Naphtho[2,3-b]thiophenium, l-methyl-X-ray, 4, 724 (81JA289)... 

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