Thiol arylation

These reactions are convenient methods for putting sulfur-containing groups onto an aromatic ring. With Ar S", diazosulfides Ar—N=N—S—Ar are intermediates, which can in some cases be isolated. Thiophenols can be made as shown above, but more often the diazonium ion is treated with EtO—CSS" or S2", which give the expected products, and these are easily convertible to thiophenols. Aryl triflates have been converted to the aryl thiol using NaST(P5) and a palladium catalyst, followed by treatment with tetrabutylammonium fluoride. See also 14-27. 

Efficient addition between various nitrile oxides and both, short (C2) and long-chain (C16) alkyl thiols, aliphatic dithiols and aryl thiols occurs rapidly at... 

Fig. 11 Bronsted plots for logk atalyst vs. pifa of aryl thiol for the methanolysis of 23a-e,...

The reaction of nitrosoarenes with alkanethiols may provide a new and simple synthetic route to iV-aryl-S-alkylsullinarnidcs which has not been mentioned hitherto62. Nitrosoarenes are frequently accessible by simple redox reactions of the commercially available arylamines or nitroarenes2,71. High yields of the desired sulfinamide may be achieved by adjusting stoichiometry, pH and solvent polarity. With aryl thiols, however, this method may not be applicable because of the very sluggish reaction (see Table 2). Whether such a synthetic route can be extended to alkylnitroso compounds remains to be established. 

A mild stereoselective synthesis of arylthioglycosides has been accomplished via anomeric inversion during the nucleophilic reaction by aryl thiols on glycosyl halides [18, 19]. 

At the time of the earlier review (66HC1155), it was already known that combinations of arenes with sulfur, or with sulfur mono- or dichlorides in the presence of Lewis acids (IV,B,1), or of aryl thiols, diaryl sulfides, or disulfides (IV,B,2 and 3) again heated with Lewis acid catalysts, generate thianthrenes, sometimes in acceptable preparative yields. A complimentary method is the treatment of aryl thiols with c. H2SO4. Routes from arenes and aryl thiols almost certainly involve the initial formation of diaryl sulfides. All these methods inevitably give symmetrical thianthrenes carrying identical substituents on each benzene ring (Scheme 9), unless the second sulfur is introduced in a controlled fashion into a preformed, unsymmetrical diphenyl sulfide. 

Endothelin receptor antagonists 134 and 135 were prepared from the triflated oxicam derivative 136 (Scheme 18) <1998BMC1447>. Addition of aryl thiol 137 to the position gave product 134. Palladium-catalyzed Suzuki coupling of aryl boronic acid 138 and aryl triflate 136 affords the sulfonamide product 135. 

The oxidation of a series of alkyl and aryl thiols in aqueous alkaline solution has been studied in the presence of various metal ions. Quantitative amounts of disulfide were produced in all cases. The oxidation rate of thiols has been found to be affected by the geometric size and electron-directing properties of substituent groups in the organic chains of the thiols. The best three catalysts, when added as simple salts, have been found to be copper, cobalt, and nickel. The dependence of the rates of oxidation on the concentrations of reactants have been investigated in some detail. 

As a preliminary to the detailed investigation of the kinetics and mechanism of the oxidation of thiols in the presence of metal-containing catalysts (8), the present paper describes a survey of the rates and end products of oxidation of a series of alkyl and aryl thiols under comparable conditions. The reaction in the absence and presence of various metal-containing catalysts has been studied under conditions of minimal impurity concentrations. 

The contention that disulfides are the major products of reaction when thiols are oxidized in aqueous alkaline solution has been amply confirmed by the present investigation. Thus, in the absence and in the presence of various metal ions (Table I) and in the oxidation of various simple alkyl and aryl thiols (Table III) disulfide has always been produced quantitatively. Under these circumstances, experiments have been designed to investigate the kinetics and mechanism of the reaction as a basis for further detailed studies. 

Aryl thiols and thioethers can be prepared in reactions similar to 3-1 and 3-4.87 Activated aryl halides generally give good results, but side reactions are occasionally important. Diaryl... 

Aryl ethers. Unlike other Bi(V) arylaling reagents, this reagent converts phenols into unsymmetrical diaryl ethers (equation 1). Yields are in the range 50-75%. Yields are improved if the phenol is treated first with Bi(C6H5)s and then with TFA. The reagent also converts aryl thiols into mixed diaryl sulfides. 

Methanethiol and other, lighter alkyl thiols are fairly common air pollutants that have ultragarlic odors both 1- and 2-butanethiol are associated with skunk odor. Gaseous methanethiol is used as an odorant leak-detecting additive for natural gas, propane, and butane it is also employed as an intermediate in pesticide synthesis. A toxic, irritating volatile liquid with a strong garlic odor, 2-propene-l-thiol (allyl mercaptan) is a typical alkenyl mercaptan. Benzenethiol (phenyl mercaptan) is the simplest of the aryl thiols. It is a toxic liquid with a severely repulsive odor. 

The simplest of the aryl thiols is benzenethiol, phenyl mercaptan (bp, 168°C). It has a severely repulsive odor. Inhalation causes headache and dizziness, and skin exposure results in severe contact dermatitis. 

The bond dissociation energy (BDE) of the S-H bond of aryl thiols is approximately 75 kcal/mole (14), which would result in the formation of a resonance-stabilized phenylthio radical. The BDE of the aromatic C-S bond is approximately 85 kcal/mole (14), and cleavage of thiophenol at the C-S bond would result in the formation of an unstable and reactive phenyl radical. Very little decomposition of neat thiophenol occurred at a reaction temperature of 375°C for 30 minutes, confirming a report in the... 

Chen and co-workers later reported the successful asymmetric 1,4-addition of aryl thiols to a,/ -unsaturated cyclic enones and imides using Takemoto s elegantly simple catalyst (3) [43]. This bifunctional amine-thiourea catalyst gives optimal reactivity and reproducibility when used at 10 mol% loading in the presence of freshly dried 4 A molecular sieves (MS). This combination afforded the expected addition products in high yields (90-99%) and moderate to good enantioselectiv-ities (55-85% ee) for a variety of cyclic and acyclic Michael acceptors (Table 6.2). 

Sulfur can be introduced into a diazonium salt by the SN1 reaction shown in Figure 5.51. In order to prevent the reagent from effecting a double (rather than a mono-) arylation at the sulfur atom, potassium xanthogenate instead of sodium sulfide is used as the sulfur nucleophile. The resulting S-aryl xanthogenate C is hydrolyzed. In this way diarylsulfide-free aryl thiol B is obtained. 

Alkyl and aryl thiols afforded with perfluoroalkyl iodonium salts in the presence of pyridine the corresponding sulphides in good to excellent yields [25], Several sulphides and sulphoxides upon reaction with trifluoroethyl phenyliodonium triflate were converted into 2,2,2-trifluoroethyl sulphonium salts [26]. 

The procedure outlined above also offers a general method for the synthesis of alkyl and. aryl thiols starting from the appropriate halides. Thus thiophenol may be obtained in 62% yield by lithiation and sulfurization of bromobenzene.8... 

Disulfides. Thiols are oxidized to disulfides by dimethyl sulfoxide. This oxidative coupling is particularly useful for coupling of aryl thiols (equation I). 

Aryl thiols. Aryllithiums react with this disulfide to form crystalline dithiocarbam-ates, which are cleaved to aryl thiols on alkaline hydrolysis (equation 1). 

The types of organosulfur compounds found in petroleum feedstocks are shown in Table Of them, the alkyl and aryl thiols (RSH), sulfides (RSR ), and disulfides (RSSR ) are the most rapidly desulfurized (equation 1). It is the broad class of thiophenes, stabilized by their aromatic character, that are most difficult to desulfurize and require relatively severe temperatures ( 400 °C) and H2 pressures ( 100 atm). Thus, it is the HDS of thiophenes that has been of greatest interest to inorganic and organometallic chemists. There are fewer model studies of the HDS of thiols, sulfides, and disulfides. Organometallic aspects of HDS and HDN have been summarized most comprehensively in a recent book by Sanchez-Delgado. A briefer overview has also been published. More specific reviews are cited in later sections of this chapter. 

Figure 7 Tailed iron porphyrins used as models of c)7ochrome P450. (a) model designed by Battersby and coworkers, attached at two points (b) TPP derivative with a pendant aryl thiol capable of bonding to the metal (c) a picket fence derivative with a pendant alkyl thiol (d) a chelated heme with a thiolate ligand (e) precursor of a model designed by Tatsimo et al., attached to the porphyrin at two points (f) another TPP derivative with a pendant aryl thiolate ...

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