Thianthrene benzene-sulfur reaction

The earliest reported reference describing the synthesis of phenylene sulfide stmctures is that of Friedel and Crafts in 1888 (6). The electrophilic reactions studied were based on reactions of benzene and various sulfur sources. These electrophilic substitution reactions were characterized by low yields (50—80%) of rather poorly characterized products by the standards of 1990s. Products contained many by-products, such as thianthrene. Results of self-condensation of thiophenol, catalyzed by aluminum chloride and sulfuric acid (7), were analogous to those of Friedel and Crafts. 

The first reported assignment of the PPS stmcture to reaction products prepared from benzene and sulfur in the presence of aluminum chloride was made by Genvresse in 1897 (8). These products were oligomeric and contained too much sulfur to be pure PPS. Genvresse isolated thianthrene and an amorphous, insoluble material that melted at 295°C. These early synthetic efforts have been reviewed (9—11). 

One route to thianthrene (70 Z, Z = S) involves reaction of sulfur monochloride with benzene over aluminum chloride (66HC(21-2)1155). 

A general route to phenoxathiins 85 (Z = O, Z = S) utilizes the reaction of diphenyl ethers with sulfur. One route to thianthrene 85 (Z, Z = S) involves reaction of sulfur monochloride with benzene over aluminum chloride. Likewise, tf-methoxyphenol reacts with sulfur dichloride to give, depending on the rate of addition of the reactant, 2,8-dihydroxy-3,7-dimethoxythianthrene 89 or l,6-dichloro-2,7-dihydroxy-3,8-dimethoxythianthrene 90 <1997JCM272>. 

The well-known reaction of elemental sulfur with benzene may follow the SN1 mechanistic pathway via the in situ formation of the benzenesulfenyl cation which immediately reacts with another aromatic nucleus to give thianthrene (59) and diphenyl sulfide (Scheme 35). 

A particularly valuable route to phenoxathiin utilizes the long-known reactions of diphenyl ether with sulfur in the presence of aluminum chloride. Thianthrene was similarly prepared from sulfur and benzene. These harsh conditions would not be suitable for the preparation of electron-rich alkoxylated dibenzo compounds (181). For the construction of compounds (181), a strategy involving electrophilic ring closure of preformed alkoxylated diaryl chalcogenides (180) was used. Thus, treatment of compounds (180) with sulfur dichloride in dry chloroform provided the derived phenoxathiins (181) in satisfactory yields <88JCS(Pl)2095>. 

Phenyl sulfide, thianthrene, and phenyl disulfide had been formed at 41 C before appearance of the colored complex. The amount of each compound peaked at different times and temperatures. Phenyl sulfide in the first major compound formed but is soon displaced by thianthrene at temperatures above 90 C. The rather large amounts of thianthrene could even have been larger, however, as part of it crystallized from the samples and did not completely redissolve. Phenylthiothianthrene was the major heavy component, the heaviest to pass through the GLC column. Thiophenol, phenyl disulfide, and phenyl trisulfide were present in small amounts throughout most of the polymerization. Bis(phenylthio)benzene was formed in small amounts during the polymerization. This is a novel product of the reaction between benzene and sulfur with AlCl and was not detected among the products in Table 1. This compound can be converted easily into phenylthiothianthrene. 

Glass and Reed in 1929 heated benzene and sulfur (1 mole to 3.1 g atoms) in a leaky bomb at 350 C for 24 hours, with a loss of 25.2% of the reactants and products. They isolated benzene, hydrogen sulfide, thlophenol, phenyl sulfide, phenyl disulfide and thianthrene plus 24.8% of tarry residue from repeated distillations. The residue was not characterized further, so any identification of it as PPS probably is wishful thinking. The reaction was repeated in a sealed glass tube but no data was given. 

Initial methods for the synthesis of thianthrene were based on the reaction of benzene with sulfur and its dichloride in the presence of aluminum chloride. ... 

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