1.4- Dichlorobenzene reaction with sulfur

Rees et a/.480 461 heated 2-methylnaphtho[l,8-cfe]triazine (505) with DM AD and EP in o-dichlorobenzene and obtained 30-40% of 2-methylacenaphtho[5,6-dehydrogenating agent this must facilitate the transformation of 506 to 507. The product is a stable 14rr aromatic system, possibly formed by a 1,11-dipolar (127r + 2n) cycloaddition. A similar reaction with the naphtho[l,8- /]thiadia-zine (508) and DMAD giving 509 was described.480... 

In early work on organosulfur compounds, Duess (I) and Hil-ditch (2) reported the preparation of various aromatic disulfides by condensation reactions of thiophenol on treatment with aluminum chloride and sulfuric acid, respectively. Macallum (3) was the first to report the preparation of a phenylene sulfide polymer. His procedure involved the reaction of sulfur, sodium carbonate, and dichlorobenzene in a sealed vessel. Polymers made by this scheme generally have more than one sulfur atom between benzene rings, as indicated by the structure —( C6H4S )w-. 

Hydroxynaphthalene-l-sulfonic add can be prepared by reaction of 2-naph-thol with chlorosulfonic acid at 0 °C in inert solvents such as o-dichlorobenzene or chloroethane. It is not available in satisfactory yields by the direct sulfonation of 2-naphthol with sulfuric add. Ammonolysis at 150 °C transforms 2-hydroxynaph-thalene-l-sulfonic acid into 2-aminonaphthalene-l-sulfonic acid (Tobias add), which, in quantity terms, is one of the most important derivatives of 2-naphthol. 

The high-temperature condensation of aromatic halides (diphenylsulfide, thian-threne, diphenyldisulfide, thiophenol and direct reactions of benzene with sulfur) in the presence of aluminium chloride was examined by Sergeyev et al. [98]. The reaction of 1,4-dichlorobenzene or 1,4-dibromobenzene with sodium sulfide at 195 °C in N-methylpyrrolidone (NMP) has been studied under normal atmospheric pressure, the kinetic of polymerization was found to be of second order. The same reaction in NMP was revised by Russian authors [99]. The polymerization of diphenyldisulfide produced PPS when stoichiometric amounts of diphenyldisulfide and antimoniumpentachloride were used in nitrobenzene at 20 °C. The S-S bond cleavage is catalyzed by the Lewis acid and the authors claim to have obtained an identic product compared with the commercial one with a molecular weight >1000 [100]. 

The discovery that the sulfonation of anthraquinone, which normally occurs in the /3-position, is directed exclusively to the a-position by a small amount of mercury has prompted investigations of the effect of mercury on other sulfonations. No instances have been found in which the course of the reaction of hydrocarbons is altered drastically. The sulfonation of naphthalene and of anthracene is unaffected. However, the course of the reaction of sulfur trioxide-sulfuric acid with o-xylene, o-dichlorobenzene, and o-dibromobenzene is affected to a certain extent. The 4-sulfonic acid is the exclusive product of sulfonation in the absence of mercury the 3-sulfonic acid is formed to the extent of 20-25% in the presence of 10% of mercury. The relative ineffectiveness of mercury in the sulfonation of hydrocarbons is understandable if it is true that the activity of mercury in the reactions of oxygen-containing compounds is due to mercuration followed by replacement with the sulfonic acid grouping. Phenols are known to be particularly susceptible to mercuration (in the ortho position), and mercury has been found to exert some effect in the sulfonation of phenols, such as a-naphthol. ... 

In 1949, Werner187 announced the synthesis of several 3-alkyl- and 2,3-dialkylbenzo[6]thiophenes by the cyclodehydration of (arylthio)-acetones with phosphorus pentoxide or zinc chloride [Eq. (5)]. The reaction has since been widely used to synthesize alkyl- and aryl-substituted benzo[6]thiophenes (Table IV). Cyclodehydration proceeds most conveniently with PPA,297 298 but concentrated sulfuric acid,299,300 hydrofluoric acid, 299 aluminum chloride in benzene301 or chlorobenzene,302 zinc chloride and hydrochloric acid,303 a melt of aluminum and sodium chlorides,304 and phosphorus pentoxide in boiling o-dichlorobenzene 305 have been less widely used. 

The major products from the reaction of arynes with thiophene and benzothiophene by addition and insertion are shown in Table 11. Benzyne from phthalic anhydride reacted with thiophene at 690° to give naphthalene and benzothiophene by 1,4-addition and loss of sulfur, and by 1,2-addition and loss of acetylene, respectively, as well as phenyl-thiophene by insertion (Fields and Meyerson, 1966d, 1967e) (Scheme 19). The ratio of naphthalene to benzothiophene was about 9 1, nearly the same preference for 1,4-over 1,2-addition as was inferred from the reaction of benzyne with dichlorobenzenes and pyridine at the same temperature, and again reflects the strong tendency of benzyne to act as a dienophile. 

In the presence of metallic lithium the reaction of 8 with 1,4-dichlorobenzene yields a linear poly(l,4-phenylene polysulfide) in which the sulfur content could be 3 sulfur atoms per phenylene unit (M as high as 12,000) [Ilia]. 

Poly(/ -phenylesulfide), PPS, (white powder, Tg 92 °C, mp 270-290 °C, 65% crystallinity) was the first melt-proccessible polymer to be doped with strong electron acceptors (e.g., ASF5) to yield highly conductive products [90]. The first laboratory synthesis of PPS was reported by Macallum [91] and involved the melt reaction of 1,4-dichlorobenzene, sulfur and sodium carbonate. A commercially product has been available as powder, film or fiber since 1973 from Phillips Petroleum under the trade name Ryton it is produced from 1,4-dichlorobenzene and sodium sulfide (high-pressure process) in a polar solvent (N-methylpyrrolidone) [92]. 

Nakayama et at. used thienyl-substituted 1,4-dithiins which are obtained from easily accessible diketosulfides for the preparation of a-oligothiophenes and isomers up to the heptamer [37b, 120]. The dithienyldiketosulfides 91-93 are prepared by the reaction of chloroaeetyl-substituted (oligo)thiophenes and sodium sulfide in almost quantitative yield and are further cyclized to the corresponding 1,4-dithiins 94-96 with L.R. in 60% yield. The extrusion of sulfur from the dithiin moiety via ylide intermediates is achieved by refluxing the dithiin in o-dichlorobenzene and results in a mixture of two possible isomers [Eq. (45)]. In the case of 2,6-di-(2 thienyl)-1,4-dithiin 94, a ratio of 13 1 of H-T3-H 3 and the 2,3 4, 2"-isomer 97 in 85% yield is obtained. The separation of the compounds by recrystallization turns out well since the a,/ -connected terthiophene is better soluble in hexane. Oxidation of the dithiin with nz-chloroperoxybenzoic add and extrusion of SO from the resulting sulfoxide in the presence of DMSO afford a mixture of H-T3-H 3 and the isomer 97 in a ratio of 22 1 and in a total yield of 90% [120]. 

Friedel [26] in 1888 by heating benzene and elemental sulfur in the presence of AICI3. A few years later Genvress published a more detailed study of this reaction [27]. Fifty years after Friedels publication McCallum described a more convenient laboratory method [28], namely, a polymerization of 1,4-dichlorobenzene with elemental sulfur and potassium carbonate. Lenz and other members of Dow Chem [29-31] tried to the problems of the McCallum method (branching and cross-linking), but a satisfactory procedure, suitable for a technical production of PPS was not found. However, heating of 1,4-dichlorobenzene with sodium sulhde in NMP as described by Edmonds and HiU yielded linear PPS. With addition of certain metal carboxylates as catalysts molar masses around 35 kDa were achieved [32]. Further variations of this approach were reported by other authors [33]. Based on this method Phillips Petroleum elaborated a technical production and commercialized PPS under the trade mark Ryton . 

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