Thianthrene 5 oxide

Adam and Lohray122 have used thianthrene 5-oxide (88) as a mechanistic probe in oxidations with transition metal peroxides. They oxidized 88 with various diperoxo complexes of chromium, molybdenum and tungsten and formulated a plausible mechanism on the basis of the products formed, 89 and 90. 

The formation of adduct is followed by fragmentation and subsequent H-atom abstraction reaction from the sulfinic acid produced. Strong acid solutions of aromatic sulfoxides like thianthrene 5-oxide (7) or phenothiazine 5-oxide (8) gives rise to ESR signals, which... 

Likewise, pyridines such as methyl isonicotinate 1999 or quinolines are readily oxidized by BTSP 1949 in the presence of HOReOs in CH2CI2 to give, after 6 h at 24°C, 98% yield of, e.g., methyl isonicotinate N-oxide 2000 [174] (Scheme 12.49). The oxidation of diphenylsulfide with BTSP 1949 and triphenylphosphine dichloride in acetonitrile results, after 60 h at room temperature, in only 12% diphenyl sulfoxide 2001 and 88% recovered diphenyl sulfide [175] (Scheme 12.49), whereas thianthrene 5-oxide 2002 is oxidized by the peroxy-Mo complex 2003 to give 58% of a mixture of 2004 to 2007 in which the trans 5,10-thioxide 2005 predominates [176] (Scheme 12.50). 

The absorption produced initially by dissolving thianthrene 5-oxide in 100% sulfuric acid, ascribed to thianthrenediium... 

Relative rates of sulfide-5-oxidation for thianthrene, its 5-oxide, and its 5,5-dioxide were 6.5 x 10 2.6 x 10 1. For the comparable iodobenzene diacetate conversion of thianthrene 5-oxide into the 5,10-dioxide (8 1, cis trans), a mechanism shown in Eqs. (4) and (5) involving rehybri-... 

Thianthrene 5-oxide is converted, in concentrated sulfuric acid, into a solution of T (62JA4798) sulfuric or perchloric acid in nitromethane can also be used (63TL993). One view is that this transformation involves homolysis of the O-protonated sulfoxide, with hydroxyl radical as byproduct, though the involvement of a dication has also been suggested (63JOC2828). 

Cyclic voltammetry of thianthrene in the presence of two molar equivalents of pyridine generates thianthrene 5-oxide and not T . Having shown 2-(pyridinium-l-yl)thianthrene to have half wave potentials, 1.45 and 1.74, different from those of thianthrene, the kinetic scheme summarized by Eqs. (16)-(19) was proposed (77JOC976). 

The prediction that thianthrenediium would react with water to give the 5-oxide was vindicated by a study conducted at -40°C in liquid sulfur dioxide, which showed that while T did not react on the coulometric time scale with water (or anisole) at that temperature, thus providing a means for generating stable solutions of T, the produced by a second oxidation did react with water to give thianthrene 5-oxide. also reacted... 

Oxidation of T to generate thianthrene 5-oxide occurs cleanly with nitrite and nitrate (72JOC2691). Incorporation of 0 from labeled nitrite was considered consistent with a process (arrows on 31) involving 31 as an intermediate and producing NO as byproduct. 

Thianthrene radical ion(l+) reacts with ammonia to produce salt 33 (X = S), alkaline hydrolysis of which afforded the sulfimine 34 (X = S, R = H) and thianthrene 5-oxide. The sulfimine was unstable in light, and hydrolyzed to the corresponding oxide by aqueous acid, but gave a stable 7V-tosyl derivative (34) (X = S, R = Ts) (72JA1026). 

Sulfur, at 345°C for thianthrene tetroxide, or at 250°C for thianthrene 5-oxide, produced thianthrene in good yields. S-Labeling experiments showed that the former took place with 80% replacement of ring sulfur and the latter took place with 91% replacement (73BCJ650), so these processes, whatever their detailed mechanism, do not involve simple reductive cleavage of the S—O bond. In accordance with this, thianthrene 5,5,10,10-tetroxide is converted into selenanthrene by reaction with elementary selenium (1896CB443). 

Treated with c. HCl (65JOC2145) or c. H2SO4, then ice (63JOC2828), thianthrene 5-oxide gave 2-substituted-products 2-chloro (in low yield) and 2-hydroxythianthrene 5-oxide, the latter being reduced to 2-hydroxythianthrene by subsequent exposure to Sn/AcOH. Thianthrene radical ion(H-) may be produced in each case thus the incorporation of phenol into the HCl reaction gave the 5-(4-chlorophenyl)thianthrenium chloride (65JOC2145) (see Section III, A, 3, b). 

The sulfurane 25 reacts with benzylamine, producing thianthrene 5-oxide and the sulfimine 36 (R = CH2Ph). The latter was hydrolyzed by sequential... 

Although thianthrene itself did not form a compound with uranyl halides or nitrate, thianthrene 5-oxide did give yellow solids U02Cl2(T0)2,... 

In 1953 Djerassi and Engle showed that stoich. RuOyCCy oxidised several sulfides to the corresponding sulfones [236]. Sulfilimines (R R S=NR ) were oxidised to sulfoximes R R S(=0)=NR by RuO /aq. Na(IO )/CH2Cl2 [432] oxidation of thianthrene-5-oxide with RuO /aq. Na(IO )/CCyO°C gave thianthrene-5,5-dioxide. Comparisons were made between the behaviour of RuO, CrO Cl and [MnO ] for these reactions, and 0-atom transfer with a possible intermediacy of [RuO ] was postulated [433]. Oxidations of RSPh to the sulfoxides and sulfones by stoich. RuOyaq. CH CN were studied a concerted mechanism may be involved for these and for similar oxidations by [RuO ] and [RuO ] " (Fig. 1.12) [434]. 

The oxidation of sulfides to sulfoxides (1 eq. of oxidant) and sulfones (2 eq. of oxidant) is possible in the absence of a catalyst by employing the perhydrate prepared from hexafluoroacetone or 2-hydroperoxy-l,l,l-trifluoropropan-2-ol as reported by Ganeshpure and Adam (Scheme 99 f°. The reaction is highly chemoselective and sulfoxidation occurs in the presence of double bonds and amine functions, which were not oxidized. With one equivalent of the a-hydroxyhydroperoxide, diphenyl sulfide was selectively transformed to the sulfoxide in quantitative yield and with two equivalents of oxidant the corresponding sulfone was quantitatively obtained. 2-Hydroperoxy-l,l,l-fluoropropan-2-ol as an electrophilic oxidant oxidizes thianthrene-5-oxide almost exclusively to the corresponding cw-disulfoxide, although low conversions were observed (15%) (Scheme 99). Deprotonation of this oxidant with sodium carbonate in methanol leads to a peroxo anion, which is a nucleophilic oxidant and oxidizes thianthrene-5-oxide preferentially to the sulfone. 

In Studying asymmetric oxidation of methyl p-tolyl sulfide, employing Ti(OPr-/)4 as catalyst and optically active alkyl hydroperoxides as oxidants, Adam and coworkers collected experimental evidence on the occurrence of the coordination of the sulfoxide to the metal center. Therefore, also in this case the incursion of the nucleophilic oxygen transfer as a mechanism can be invoked. The authors also used thianthrene 5-oxide as a mechanistic probe to prove the nucleophilic character of the oxidant. 

Conformational evidence of thianthrene, thianthrene 5-oxide, and as- and /ra r-thianthrene 5,10-dioxides has been reported by studing FI NMR spectra in different solvents (CD2CI2, toluene-r/g, THE-r/g THE = tetrahydrofuran) and at various temperatures (from 25 to —130°C) (see Section 8.12.4.3) <2005JOC3450>. 

Data on the apparent dipole moment and H NMR spectra of thianthrene-5-oxide 24 under different conditions of solvent and temperature support the rapid conformational equilibrium of 24, which flaps between two limit boat conformations with the sulfoxide group in a pseudoaxial or pseudoequatorial position, respectively. Variable-temperature... 

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