Tetrathiocine

When Ba is treated with aqueous THF at reflux, a mixture of C and tetrathiocins D and E is formed in ratios that depend from the heating time. 

Other heterocyclic compourtds containing four sulfur atoms - tetrathiocines 196, 197 - were synthesized from activated aromatic compounds, in particular 1,2-dialkoxybenzenes or 2,3-dialkoxynaphthalenes, and sulfur monochloride in acetic acid in fairly good yields (1989PS111 Scheme 97). Biphenyl 154 treated with S2CI2 under the same conditions yielded 1,2-dithiines (see Section 4.3). 

The controlled potential macroelectrolysis of pentathiepin 11 using a glassy carbon cathode was conducted at —0.85 V in dimethylformamide (DMF) containing 0.1 mol dm 3 Et4NOTs and produced tetrathiocin in a high yield (Equation 5) <1997MI2399>. 

Moreover, it was found that tetramerization of 3,4-bis(methoxycarbonyl)-l,2-dithiete 19f took place selectively to give the unsaturated 16-membered cyclic compound 127 together with a small amount of tetrathiocin 128 under various conditions (Equation 16) <2000JOM(611)106>. 

The initial formation of the benzodithiete 19e, as an intermediate in the reaction of benzyne with elemental sulfur, was suggested on the basis of its secondary reaction that traps another benzyne molecule to give thianthrene 139, or o-C6U4S2 19e to give tetrathiocin 140 (Scheme 17) <2004JOC5483>. 

Disproportionation of 3,4,7,8-tetrakis(methoxycarbonyl)-l,2,5,6-tetrathiocine 226 in acetonitrile at room temperature led to the thiete 225 in 13% yield and the macrocyclic compound 227 (Equation 47) <1998JOC8192>. 

Tetrathiocine 3 was first synthesized in 1996 <1996AGE2357> (see Equation (28) in Section 14.09.9.1.2). Among several conformers optimized for 3 at local minima by ab initio (MP2/D95 ), the twist boat form 4 was calculated to lie on the lowest potential level. The calculations indicate that the energy difference between the two... 

The chair-folded structure of the 1,4,5,6-tetrathiocine ring in 20 was first suggested from the 13C NMR spectrum, which showed three resonance signals, and then confirmed by single crystal X-ray diffraction <1994IC4537> (Section 14.09.3.3). 

A weak Ss" peak was observed in the electron impact mass spectrum of the 1,2,5,6-tetrathiocine 21 indicating the absence of polysulfide linkages (see Scheme 4 in Section 14.09.10) <1994IC4537>. Formation of the mixed oxidation state [S(iv) and S(vi)] heterocycle 22 has been confirmed by a strong molecular ion in the electron impact mass spectrum <2000IC1697>. 

The ultraviolet spectra of 1,2,5,6-tetrathiocines 23 (Amax 350nm, e 7500) and 24 (Amax 361 nm, e 36000) were helpful in the comparison of their photochemical reactivity (see Section 14.09.5) <2002BCJ2647>. 

Electrochemical studies of a novel tetrathiocine 11 (Section 14.09.2) was performed by cyclic voltammetry and showed two reversible redox waves <2002TL5825>. 

X-Ray crystallography has confirmed the existence of 1,2,5,6-tetrathiocine 3 as the twisted conformer 4 (see Section 14.09.2) <1996AGE2357>. The fluoro-substituted dibenzo-l,2,5,6-tetrathiocine 6 (X = F) adopts the chair conformation 8 in the crystalline state, while the chloro compound 6 (X = Cl) was found in the twist boat conformation 7 in solid state (see Section 14.09.2) <1998CJC1093>. The calculated difference in the energies of the two conformers 7 and 8 for the fluoro-substituted derivative 6 is very small (<5 kj mol-1), and its slow conformational isomerization in solution was... 

Irradiation of the 1,2,5,6-tetrathiocine 24 in CH2C12 at room temperature resulted in the mixture of two products, the dithianthrene 25 and trithiepine 26 (Equation 3) <2000TL1801, 2002BCJ2647>. In turn, the trithiepine 26 can be further desulfurized on irradiation to give the dithianthrene 25. 

Photolytic desulfurization of the tetrathiocine 27 bearing the sterically hindered substituents resulted in the dithianthrene 28 in high yield (Equation 4) <1999TL9101>. 

In the nucleophilic elimination of sulfur, the tetrathiocine 29 underwent transformation into a mixture of which the isolated benzocyanate 30 was the major product (Equation 5) <1995T2533>. 

The Hg2+-promoted hydrolysis of the thiocarbonyl groups was accompanied with an unexpected ring rearrangement in the 1,2,5,6-tetrathiocine 21 (Section 14.09.3.2) and produced the 1,2,3,6-tetrathiocine 20 (Section 14.09.3.1) (Equation 6) <1994IC4537>. 

Photolysis of the 1,2,5,6-tetrathiocine 31 promoted a reversible, transannular sulfur migration to give 1,2,3,6-tetrathiocine 32 (Equation 7) <1998CJC1093>. The photoisomerized product 32 was readily distinguished by the 19F NMR spectrum, which exhibits an AMXY pattern. 

Since 1,2,5,6-tetrathiocine 3 (see Sections 14.09.2 and 14.09.9.1.2) is unstable toward irradiation and even room light, upon irradiation in a benzene solution, the thiocine 3 formed the bicyclic compound 33 in low yield together with a polymer, as the main product (Equation 8) <1996AGE2357>. Irradiation of 3 in the presence of a large excess of 2,3-dimethylbutadiene hindered the formation of the polymer, and the bicyclic product 34 was obtained together with a small amount of the symmetrical bicycle 33 (Scheme 1) <1996AGE2357>. This indicates the formation of the intermediate thioaldehyde 35 by photochemical rearrangement of thiocine 3, while several mechanisms are plausible for the formation of the symmetrical 33. 

In the study of S3 sources, the interaction of the tetrathiocine 36 with norbornene yielded a mixture of the thiophene 37 and 3,4,5-trithiatricyclodecane 38 the products were derived from sulfur extrusion by the retro-Diels-Alder reaction and sulfur trapping, respectively (Equation 9) <2004JA9085>. 

The reaction of lithiated benzo[ ]furan 93 with sulfur resulted in a novel heterocyclic system, bis(benzo[4,5]-furo)[2,3-< 3. 2 -g][l,2,3,4]tetrathiocine 95, possibly formed via intermediate pentathiepine 94 (Scheme 5) <2002JOC6220>. The assumed mechanism was based on the reported transformation of a pentathiepine into a tetrathiocine induced by Et3N <2001T7185> (cf. Section 14.09.10). 

The preference for formation of the tetrathiocine structure was also demonstrated by the conversion of thiol 96 into 95 (Equation 32) <2002JOC6220>. 

In the study of the controlled elimination of one sulfur atom from the trithiols 112 to generate the benzo-dithietes 113, the 1,2,5,6-tetrathiocines 115 were isolated in high yield (Scheme 8) <1995T2533>. It was suggested that the equilibrium between the benzothiete 113 and o-dithiobenzoquinone 114 should favor dimerization to form 115. 

Dithiastannole 117 was coupled oxidatively into the sterically hindered 1,2,5,6-tetrathiocine 27 in good yield (Equation (37) see Equation (4) in Section 14.09.5) <1999TL9101>. 

Ferrocene dithiastannole 119, a synthetic equivalent of an unstable ferrocene 1,2-dithiol, reacted with iodine under conditions of deprotection to give the tetrathiocine 11 (mp>300°C), as a single diastereomer (Equation (38) see Sections 14.09.2 and 14.09.4) <2002TL5825>. 

Transformation of pentathiepine 124 to 1,2,3,4-tetrathiocine 126 (mp 250-255 °C) proceeded in the presence of triethylamine in EtOH in high yield (Scheme 9) <2001T7185>. The proposed mechanism involves the intermediate formation of the dithioisatine 125 (cf. Scheme 6). Alternatively, the octameric 126 was isolated on sulfurization of 3,3 -biindole 89 in 19% yield <2002JP1330> (see Equation (30) in Section 14.09.9.1.3). 

The first example of an enzymatic cleavage of trithiocarbonate 127 followed by oxidative dimerization was reported to give an inseparable mixture of 1,2,5,6-tetrathiocines 128 and 129 (Equation 40) <2002TL2589>, whose structure assignments were based on mass spectrometry data. 

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