Aromatic disulfides

Organic sulfur compounds such as sulfurized spermaceti oil, terpene sulfides, and aromatic disulfides have been used. Encumbered phenols such as di-tertiary-butylphenols and amines of the phenyl-alphanaphthylamine type are effective stopping the kinetic oxidation chain by creating stable radicals. 

Cyclic 1,2-diketones, 24 594 Cyclic acrolein acetals, 2 271 Cyclic amidine curing agents, 10 410 Cyclic amidines, 10 412 Cyclic (aromatic disulfide) oligomers, 23 712... 

Cyclic aromatic disulfides, polymerization reactions of, 23 706 Cyclic (arylene) disulfides, 23 712 Cyclic batch adsorption processes, 1-613 Cyclic bis(arylene tetrasulfide)s, 23 712 Cyclic carbon, polymer materials with, 15 177... 

The oxidation of a mixture of aromatic disulfides, Ph2S2 or T0I2S2, with 2,2,2,-trifluoroethylamine affording arylsulfany-lation of the amino group was reported (Eq. 23) [138]. 

Similar behavior of other aromatic disulfides and thiols on gold electrodes has been described based on the SERS experiments [167]. Adsorption of benzenethiol, benzenemethanethiol, p-cyanobenzenemethanethiol, diphenyl sulfide, and dibenzyl sulfide was studied on the roughened gold electrode. All these species adsorb dissociatively as the corresponding thiolates. Monolayers formed from symmetric disulfides were exactly like those formed from the corresponding thiols. These monolayers were stable in a wide potential window from -1-800 to —1000 mV (versus SCE), which was limited by the oxidation of the Au surface from the positive side and hydrogen evolution at —1000 to —1200 mV at the negative side. 

This mechanism is analogous to that of mercury thiophenolate [135], but different from the reduction mechanism of aromatic disulfide(I). 

Observations Dimethacrylate aromatic disulfide monomeric derivatives were prepared... 

Although the synthesis has long been known, the recent patent literature contains a number of Japanese applications 621 625) claiming special process variants. The reaction is also possible with aromatic disulfides 626) ... 

These sulfur-containing macrocycles had been prepared under pseudo-high dilution conditions, but Hay and coworkers demonstrated that the cyclodepolymerization of aromatic disulfide polymers was an efficient and easier... 

Fig. 27 Synthesis of cyclic aromatic disulfide oligomers by copper catalytic oxidation reaction...

In the synthesis of a series of cyclic aromatic disulfide oligomers using oxidative coupling of dithiols with oxygen catalyzed by copper salts and an amine, an effective, easy, and rapid method for the synthesis of macrocyclic aromatic disulfide oligomer from 4,4/-oxybis(benzenethiol) by cyclodepoly-... 

Hauptmann et al. found that aromatic disulfides, thioesters, and thiols were transformed into thioethers when refluxed in xylene (140°C) in the presence of Raney Ni degassed at 200°C.130,134,135 However, when these compounds were heated at 220°C with degassed Raney Ni or reduced Ni, biphenyls were obtained in good yields. The yields of the products with Raney Ni degassed at 500°C were never lower and were sometimes higher than those obtained with Raney Ni degassed at 200°C, as seen from an example shown in eq. 13.64. On the basis of these results, it was concluded that the presence of hydrogen was not essential for these desulfurizations.136... 

Since Otsu s investigations [222] showing that aromatic disulfides or tetrasulf-ides such as 46 and 47 are the most reactive owing to their high transfer constant [21] a variety of functionalized and substituted aromatic disulfides has been... 

Most of the studies concerning the formation and decay mechanisms of (RS.-. SR)- radical anions have been performed on aliphatic disulfides in aqueous solutions. Since the solubility of aromatic disulfides (ArS-SAr) is very poor in water, their radical anions (ArS.-. SAr)- can be easily investigated in organic solvents. A dissociation mechanism of the S-S bond in the a,a -dinapthyl disulfide radical anion (NpS.. SNp)" in dimethylformamide (DMF) solutions was investigated by pulse radiolysis and in methyltetrahydrofuran (MTHF) rigid glasses by y-radiolysis. ... 

In the seccHid part, surveys concerning telechelk telomers ate mentioned. The different telc ens used and their known transfer-constants are supplied alijAatic and aromatic disulfides, disubstituted benzoyl disulfides, functional xanthogens and polyhalogenated compounds. Also novel monoaddition reactions of functional monomers onto both end groups of dithiols and ditrichloromethyl compounds are summarized. 

They are used the most. The first investigitions were carried out by Costanza and Pierson [68, 76] on styrene with aromatic disulfides especially. These authors showed that the aliphatic disulfides are not very reactive even though the aliphatic R—SH thiols are very good transfer agents. For instance, the transfer constant of Bu—S—S— Bu is 1.54x 10" at 55 °C [77] and 6.80x 10 at 99 °C [78]. 

The results from the aromatic disulfides on both styrene (Table II) and MM A (Table 12), on which Japanese teams performed a lot of investigations, are move interesting. 

TaUe 10. Comparison between the transfer constants of non-aromatic disulfides with various monomers... 

Finally, Okano et al. [84] have recently prepared an aromatic disulfide with isocyanate end group according to the reaction ... 

Table 11. Transfer constants to the styrene of monosubstituted aromatic disulfides [68, 76]...

The mechanism of the anodic oxidation of aromatic disulfides at Pt in MeCN and CH2CI2, was reexamined [43]. In CH2CI2, under neutral conditions, the oxidation is a two-electron process leading to a sulfenium cation, RS , whereas in MeCN a dicationic species is postulated as intermediate that can partially evolve toward [Eq. (13)]. The sulfenium cation seems to be very stable in solution even during several days. 

The rate constant of the heterogeneous electron transfer from a platinum electrode to aromatic disulfides in DMF is low, whereas the homogeneous electron transfer from suitable radical anions is much faster these can be generated at potentials more negative than eP of the disulfides but less negative than their peak potentials [223]. 

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-. 

Analogous [4-1-1] annulations were also obtained starting from isonitriles and f-cyano-substituted sulfanyl radicals, generated either by hydrogen abstraction from aliphatic thiols or (more profitably) through photolysis of aromatic disulfides [18]. The reactions afforded thieno- (24) and benzothienoquinoxalines (25), respectively (Scheme 10). 

Finally, a novel three-component radical cascade reaction involving isonitriles has just been published [6]. In this paper, aromatic disulfides, alkynes, and isonitriles have been reported to react under photolytic conditions to afford -arylthio-substituted acrylamides 49 or acrylonitriles 50 in fair yields as mixtures of the E and Z geometric isomers (Scheme 21). The procedure entails addition of a sulfanyl radical to the alkyne followed by attack of the resulting vinyl radical on the isonitrile. A fast reaction, for example, scavenging by a nitro-derivative (route a) or f-fragmentation (route b), is necessary in order to trap the final imidoyl radical, since addition of vinyl radicals to isonitriles seems to be a reversible process. The reaction provides very easy access to potentially useful poly-functionalized alkenes through a very selective tandem addition sequence. 

Disulfides are also formed in good yield when alkyl or aryl halides react with sodium disulfide. According to Blanksma,280 who prepared many aliphatic and aromatic disulfides by this method, the halide is heated with an equivalent amount of sodium disulfide in alcoholic solution. In this way have been prepared, inter alia, bis-(o-nitrophenyl) disulfide (62%),281 dithiodi-(malonic acid),250 and 2,2 -diphenyl-2,2 -dithiodi(acetic acid).251... 

Thioanisole (methyl phenyl sulfide) and aromatic disulfides can be cleaved at the C-S bond by A -bromosuccinimide, whereby good yields af TV-(arylthio)-... 

A completely different approach to the synthesis of this sulfide was explored through the reaction of cyclopropyllithium with an aromatic disulfide, thus avoiding the base-promoted cyclization step. A solution of 2.6 g di-(2,5-dimethoxyphenyl)disulfide (from... 

This mildly exothermic combination turned a bit cloudy, was stirred for 1 h, then trans-ferred with an air-tight syringe to the above-described Et20 solution of the aromatic disulfide. A heavy precipitate formed, and stirring was continued for an additional 0.5 h. The reaction mixture was then poured into H20, the layers separated, and the aqueous phase extracted with CH2CI2. The extracts were pooled, washed with dilute aqueous KOH, and the solvents removed under vacuum. Distillation gave 0.7 g of 2,5-dimethoxyphenyl cyclopropyl sulfide with identical gas chromatographic behavior to the sample prepared by the cyclization of the chloropropylthio compound. 

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