Phenoxathiines

Quite recently, it was reported that heating of tetracyano derivative 268 with potassium nitrite and potassium carbonate in DMF provided 53% of phenoxathiin 270 (Scheme 42) (OOlHl 161). The probable mechanism is, that one activated nitro group in 268 is displaced with a nitrosoxy group by nucleophilic substitution of nitrite ion, followed by hydrolysis to 269, which then undergoes denitrocyclization reaction to the final product. 

Smiles rearrangement was observed also in base-catalyzed cyclization of 2-hydroxy-2 -nitrodiphenylsulfones leading to low yields (about 5%) of phenoxathiine 10,10-dioxides (34JCS422, 56JA5357). However, this type of compounds can be easily prepared by other methods (05CB1411, 06CB1340). 

Carbazole, A-methylcarbazole, IV-ethylcarbazole, dibenzofuran, dibenzothiophene, fluorene, dibenzo-p-dioxin, phenoxathiin, phenoxazine, phenothiazine, xanthene, biphenyl, naphthalene, phenanthrene, anthracene, and fluoranthene could be transformed by E. coli, [314] which was transformed using a plasmid bearing the carAa, Ac, and Ad genes, and expressing only the carA-encoded proteins. Further work is needed to develop a final biocatalyst and to prove the advantages that this degradative pathway would incorporate in a refining bioprocess. 

Dibenzofuran is also formed when phenoxathiin is desulfurized by bis( 1,5-cyclooctadiene)nickel(O) and 2,2 -bipyridyl, but limited synthetic application can be envisaged for this type of reaction despite the high yield obtained (see Scheme 77).140... 

The perchlorate salts of the bis-adducts of thianthrene (X = S) or phenoxathiin (X = O) with substituted acetylenes explode on heating. 

Another point worth mentioning is the selectivity of the electrogenerated electrophilic sulfur species toward aromatic substrates in the reaction with diphenylether and diphenylamine. In the first case, an internal ortho-cyclization yields in phenoxathiin, in the second, a para-substitution occurs [252] giving a linear product (8cheme 59). 

Ru (0)2(por " )] (for por = TMP and OEP) have been generated by oxidation of [Ru (0)2-(por)] with phenoxathiin hexachloroantimonate. The products show a broad Q band and a less intense and blue-shifted Soret band, consistent with the formation of the porphyrin cation radical. 

Phenoxanthin, 68 X = S Y = O, is prepared by the electrochemical oxidation of diphenyl ether in dichloromethane and trichloroacetic acid containing tetraethyl-ammonium perchlorate at a composite anode of carbon and sulphur. The anode generates sulphur cations, which carry out electrophilic substitution on the benzene ring [237], Phenoxathiin radical-cation, formed at the potential of the fust oxidation wave, has been characertised by esr spectroscopy [238],... 

Aminophenoxathiin 319 was synthesized from the oxime derivative 318 of 3-acetyl-phenoxathiin ° (equation 116). 

Winningham MJ, Sogah DY. A modular approach to polymer architecture control via catenation of prefabricated biomolecular segments polymers containing parallel /8-sheets templated by a phenoxathiin-based reverse turn mimic. Macromolecules 1997 30 862-876. 

The H and nuclear magnetic resonance (NMR) chemical shift of all the parent structures are fully reported in CHEC-II(1996) <1996CHEC-II(6)447>. Since then, the complete proton and carbon chemical shift assignments have been made for 2- and 3-formyl, acetyl, or methyl phenoxathiin <1996PJC36>. 

Phenoxathiin and thianthrene can be chlorinated without oxidation into the corresponding sulfoxides using sulfuryl chloride and AICI3 to form the 2,3,7,8-tetrachloro derivatives 41 and 42, respectively. Use of BMS reagent- a mixture of sulfur monochloride, sulfuryl chloride, and aluminium chloride - results in exhaustive chlorination of phenoxathiin and thianthrene with formation of perchlorinated products 43 and 44. It is noteworthy that using sulfuryl chloride in dichloromethane, the sulfoxides were isolated as the major products <1997CHE333>. 

Many oxidizing agents have been used to afford almost all the possible oxide derivatives of 1,4-dithiin, 1,4-benzoxathiin, 1,4-benzodithiin, thianthrene, and phenoxathiin <1984CHEC(3)943, 1996CHEC-II(6)447>. 

Dithiin, 1,4-benzodioxin, and its 2-substituted derivatives can be readly deprotonated and trapped with electrophiles although the reaction is more problematic with 1,4-dioxin. Oxanthrene and phenoxathiin are cleaved with lithium <1996CHEC-II(6)447>. A more recent example deals with the metallation at C-3 of the 1,4-benzodioxane 60 bearing a carboxylic acid function at C-2, with lithium diisopropylamide (EDA) and subsequent quench with iodomethane. The corresponding 3-methylated benzodioxane 61 was isolated in 70% yield (Equation 6) <2000EJM663>. 

The preparation of a number of 5-(alkyl)thianthrenium perchlorates has been performed from the thianthrene cation radical with dialkylmercurials and tetraalkyltins (R4Sn) <1983JOC143>. Thianthrene as well as phenoxathiin cation radical perchlorates react with alkenes. The former add stereospecifically to cycloalkenes although the latter afforded a mixture of mono- and bis-adducts in which the configuration of the alkene was retained <2003JOC8910>. 

In the rings containing sulfur, reduction of sulfoxides of phenoxathiin and thianthrene can be performed in excellent yield with the aluminium chloride/sodium iodide or zinc dust/l,4-dibromobutane systems <1996CHEC-II(6)447>. 

Dicyanodibenzodioxin as well as tetracyano derivatives of thianthrene and phenoxathiin have been synthesized by aromatic nucleophilic substitution reaction of the bromine atom and nitro group in 4-bromo-5-nitrophthalonitrile <2001H(55)1161>. 

Phenoxathiins were intensely studied in order to obtain new antifungal, antibiotic, anti-inflammatory, antiedema, antidiabetic, cholerethic, cytostatic, and tranquilizer drugs, or insecticides <1984CEIEC(3)943, 1996CEIEC-II(6)447>. 

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