Benzenethiol, substituted

Cyano-de-diazoniations of the Sandmeyer type have been used for the synthesis of aromatic nitriles for many decades (example Clarke and Reed, 1964), as cyanide ions are comparable to bromide and iodide in many respects. A homolytic cyano-de-diazo-niation that does not use metal ions as reductant or ligand transfer reagent was described by Petrillo et al. (1987). They showed that substituted diazosulfides (XC6H4 — N2 — SC6H5), either isolated or generated in situ from arenediazonium tetrafluoroborates and sodium benzenethiolate, react with tetrabutylammonium cyanide in dimethylsulfoxide under photon stimulation, leading to nitriles (XC6H4CN). The method worked well with eleven benzenediazonium ions substituted in the 3- or 4-position, and was also used for the synthesis of phthalo-, isophthalo-, and tere-... 

Novi and coworkers124 have shown that the reaction of 2,3-bis(phenylsulfonyl)-l,4-dimethylbenzene with sodium benzenethiolate in dimethyl sulfoxide yields a mixture of substitution, cyclization and reduction products when subjected at room temperature to photostimulation by a sunlamp. These authors proposed a double chain mechanism (Scheme 17) to explain the observed products. This mechanism is supported by a set of carefully designed experiments125. The addition of PhSH, a good hydrogen atom donor, increases the percent of reduction products. When the substitution process can effectively compete with the two other processes, the increase in the relative yield of substitution (e.g., with five molar equivalents of benzenethiolate) parallels the decrease in those of both cyclization and reduction products. This suggests a common intermediate leading to the three different products. This intermediate could either be the radical anion formed by electron transfer to 2,3-bis(phenylsulfonyl)-l,4-dimethylbenzene or the a radical formed... 

The low specificity of electron-donating substrates is remarkable for laccases. These enzymes have high redox potential, making them able to oxidize a broad range of aromatic compounds (e.g. phenols, polyphenols, methoxy-substituted phenols, aromatic amines, benzenethiols) through the use of oxygen as electron acceptor. Other enzymatic reactions they catalyze include decarboxylations and demethylations [66]. 

In the former case, the dibromo- or dichloro-substituted arene is reacted with cuprous or sodium thiolates to give vicinal thioethers, which can be reductively dealkylated, for example with Na/NH3, to give the dithiols.63 Alternatively, benzenethiol is reacted with ra-BuLi, and the resulting lithiated product is made to react with elemental sulfur to give the 1,2-dithiolate salt. 

Substituted thioindigoid dyes are usually obtained via the appropriate benzenethiol in a Heumann-type synthesis. The final cyclisation of the phenylthioglycolic acid derivative can often be achieved in concentrated sulphuric acid or by using chlorosulphonic acid. Several routes make use of the Herz reaction (Scheme 6.22), in which a substituted aniline is converted into the corresponding o-aminothiophenol by reaction with sulphur monochloride followed by hydrolysis of the intermediate dithiazolium salt [47]. After reaction between the thiol and chloroacetic acid, the amino group is converted into a nitrile group by a Sandmeyer reaction. Hydrolysis of the nitrile leads to the formation of the required thioindoxyl derivative. 

Interaction of substituted arenediazonium salts with potassium O. O-diphenylphosphorodithioates gave a series of solid diazonium salts which decomposed explosively when heated dry [10], The unique failure of diazotised anthranilic acid solutions to produce any explosive sulfide derivatives under a variety of conditions has been investigated and discussed [6]. Preparation of diaryl sulfides from interaction of diazonium and thiophenoxide salts led to violent explosions, attributed to presence of some arenediazo sulfide during subsequent distillation of the diaryl sulfides. Precautions are detailed [11]. A safe method of preparation of diaryl sulfides from diazonium tetralluoroborates and sodium benzenethiolate in DMF is now available [12],... 

Oxetanones can be generally prepared by displacement processes on various /3-substituted carboxylic acids or by halolactonization of /3,y-unsaturated acids. A very general and reliable method consists of treatment of a /8-hydroxy acid with benzenesulfonyl chloride and pyridine at 0°C (equation 91). The yields of /3-lactones are usually in excess of 80% (79JOC356, 74JOC1322). An alternative method involves cyclization of the benzenethiol ester of a /3-hydroxy carboxylic acid by means of mercury(II) methanesulfonate in acetonitrile (equation 92). The yields were excellent in the two cases reported (76JA7874). 

For substituted tricyclo[4.1.0.02,7]heptanes, similar addition of benzenethiol in diethyl ether gave an isomeric mixture of bicyclo[3.1.1]heptanes.35 As shown in the mechanistic scheme, the 1,3-disubstituted patterns of the bicyclo[3.1, l]heptanes are governed by the regiospecific attack of the thiol radical on the sterieally less hindered bridgehead carbon. The results of these radical additions arc summarized for bicyclo[n.l.l]alkanes (Table 8)35 and bicyclo[1.1.0]butanes (Table 9). 

In the presence of proton and/or Lewis acid and strong nucleophiles bicyclo[3.2.0]heptan-6-ones are converted to 3-substituted cycloheptanones (Table 15). Bicyclo[3.2.0]heptan-6-ones rearrange to give 3-iodocycloheptanones on treatment with iodotrimethylsilane. Zinc(II) iodide or mercury(II) halides as catalysts enhance the rate and the selectivity of the reaction.31 If a second, enolizable carbonyl group is present, an intramolecular alkylation may follow the ring enlargement under these reaction conditions.32 Consecutive treatment with tributyltin hydride/ 2,2 -azobisisobutyronitrile affords reduced, iodo-free cycloheptanones, whilst treatment with l,8-diazabicyclo[5.4.0]undecene yields cycloheptenones.33 Similarly, benzenethiol adds to the central bond of bicyclo[3.2.0]heptan-6-ones in the presence of zinc(II) chloride and hydrochloric acid under anhydrous conditions to form 3-(phenylsulfanyl)cycloheptanones.34... 

Very little work has been done on fluoro derivatives of thiophenes. 2-Fluorothiophene was obtained in low yield from treatment of 2-iodothiophene with arsenic trifluoride. The action of fluoroboric acid on thiophenediazonium salts was unsuccessful. It may be useful for the preparation of 4-, 5-, 6- or 7-fluorobenzo[6]thiophenes from the appropriate amines. However, these are more conveniently prepared from fluorine-substituted benzenethiols by ring-closure reactions. For example 4,5,6,7-tetrafluorobenzo[6 Jthiophene was obtained by decarboxylation of the corresponding 2,3-dicarboxylic acid (equation 99) prepared by condensation of pentafluorobenzenethiol with diethyl acetylenedicarboxylate (Section 3.15.3.4.1). 2-Fluorothiophene has been prepared from 2-thienyllithium using perchloryl fluoride, and 2-fluorobenzo[ Jthiophene from the 2-lithio derivative in a similar manner (Section 3.14.3.9.1). 

The broad applicability of dimethylformamide as the reaction medium is further shown by the reaction of other types of fluoroheterocycles. such as 3-fluoro- or 4-fluorophthalic anhydride, with substituted benzenethiols, which at low temperatures and with weak bases, e.g. sodium carbonate, provides the respective sulfides in excellent yield.25... 

Nucleophilic Substitution Reactions. Many of the transformations realized through Michael additions to quinones can also be achieved using nucleophilic substitution chemistry. In some instances die stereoselectivity can be markedly improved in this fashion, e.g., in the reaction of benzenethiol with esters (R = CH3C=0> and ethers (RJ = CH,) of 1,4-naphthoquinones. 2-Bromo-5-acetyloxy-1,4-naphthoquinone, R1 — Hr, yields 75% of 2-thiophenyl-5-acetyloxy-1,4-naphdloquinone. R1 = SCr.Hv 3-Bronio-5-methoxy-l,4-naplitlioquinone, R2 = Br, yields 82% of 3-thiophenyl-5-methoxy-1,4-naphthoquinone R2 = SCr.IIs. 

The report by Bunnett and coworkers107 of substitution of halide by MeCOCth" or PhS- ions in vinyl bromides or iodides appears to be the only synthetic application of the SrnI reaction at vinylic sites. The reactions, particularly with benzenethiolate ion, are slower than those of aryl halides and the yields are not as good. Tautomers or mixtures of products result in the reactions with MeCOCH2 (e.g. equation 32). 

A variety of substituted aromatic compounds have been prepared through addition of anionic nucleophiles to arynes generated from readily accessible precursors.1 Most of the laboratory preparations start with aryl halides. The coupling yields are usually good to modest (equations 13-15) but can be poor (equation 16).83 Sometimes, a dramatic improvement in reaction efficiency can be achieved by the change of the base/solvent pair or other reaction conditions. For instance, in arylation of phenoxides and benzenethiolates, a switch over to DMSO as the solvent boosted the yield considerably (equation 17).86 Another example, illustrative of this point, is the reaction of N-methylpyrrolidone with aryl halides where an acceptable yield could not be obtained under a variety of conditions except with LICA in THF (equation 18).71... 

Product analyses not performed but, by analogy with results from benzenethiolate (which yielded 96% elimination product, DDE 17311. no substitution products expected. 

The polycondensation of dibromomethane with bis(benzenethiol) instead of bisphenol also shows stoichiometrically imbalanced polymerization behavior (Scheme 63) [253]. When 1.5 equivalents of dibromomethane was reacted with dithiol in NMP at 75 °C for 4 h, polysulfide with the maximum inherent viscosity (//jn, = 0.50 dbg ) was obtained. On the basis of the model reaction, a reactive intermediate, in which a bromine in dibromomethane is substituted with the mercapto group of the monomer, is estimated to be 61 times more reactive than dibromomethane. 

Halomethyl)-5-nitrofurans have been reported to give a substitution product with the anion of 2-nitropropane75a by the S l mechanism, whereas with different thiolates ions75b they react by an S 2 mechanism. Recently the reactions of 2-(bromomethyl)-5-nitrofuran with benzenethiolate and 4-chlorobenzenethiolate ions were assumed to be S l substitutions750. 

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