Thioethers from thiols

ETHERS, EPOXIDES AND THIOETHERS FROM ALCOHOLS AND THIOLS... 

A superior and relatively versatile procedure for the synthesis of unsymmetrical dialkyl thioethers, which avoids the unattractive direct use of thiols, utilizes the stable l-alkylthioethaniminium halides, which are readily obtained from thioacet-amidc [32] (Scheme 4.4). The reaction has also been used for the synthesis of alkyl aryl thioethers from activated aryl halides [33], but it cannot be used for the synthesis of cyclic thioethers, as polymeric sulphides are formed from a,co-dihaloalkanes. A similar sequence to that which leads to the thioethers has been used for the synthesis of S-alkyl thioesters [34] (see 4.1.26). 

Table 8.4. Preparation of thioethers from support-bound thiols.

SECTION 123 Ethers, Epoxides, and Thioethers from Alcohols and Thiols... 

The catalytic oxidation of sulfur-containing compounds has been studied mostly on the examples of thioethers and thiols, which are most often encountered in petrochemical industry. Elimination of the foul odor arising from thiols (mercaptans) contained in some oils ("sweetening") is mostly carried out by oxidation of thiols to disulfides. The oxidation of sulfur salts is also of practical importance in the processing of sulfide ores and handling the... 

It also appears that thiol pyruvate can serve as sulphur donor for some biological transsulphurations. The thiol nucleotides which occur in small quantities in certain nucleic acids appear to derive their sulphur, at least in part, from thiol pyruvate rather than directly from cysteine. While these reactions have not been extensively studied as yet, ATP is required possibly to activate a group for intermediate thioether formation. Pyruvate elimination could then proceed through an enolate or an intermediate enzyme-bound Schiff base. 

By performing the hydrolysis of thioesters in the presence of benzylic alcohols, transprotection of thiols could be successfully carried out in water. The reactions proceeded smoothly to give benzylic thioethers from thioesters in good yields (Scheme 3.35). 

Enol phosphates derived from thiol esters couple with organoaluminium reagents, catalysed by tetrakis(triphenylphosphine) palladium, to form enol thioethers, and hence ketones by hydrolysis [equation (22)]. This alkylative... 

Primary amines and thiols undergo similar elimination with Al(III)-exchanged montmorillonites. Primary amines are converted at 473 K to di-alk-l-ylamine by loss of ammonia. Likewise, hydrogen sulfide is eliminated from thiols to form di-alk-l-yl thioethers. ... 

In contrast to oxygen, sulfur has been far less widely used as a nucleophile for addition to ruthenium vinylidenes. The formation of vinyl thioethers from the addition of thiols to aUcynes catalyzed by binuclear ruthenium complexes Cp Ru (p-SR)2RuCp (R=Et, i-Pr, f-Bu) and related complex Cp Ru(p -C6F5)(p-S) (p-SC6F5)RuCp has been described [112]. 

A suspension of cuprous oxide promotes nucleophilic substitution in aprotic polar solvents at e. g. 150-200°. Effective nucleophiles are the anions ArO , AlkO , ArS , AlkS , CN", I, Br , and Gl phenols and thiols may be used in place of their salts.—E Thioethers from halides. 1-Bromonaphthalene and Na-thio-phenoxide heated 24 hrs. at 153° in dimethylformamide containing CugO -> 1-phenylthionaphthalene. Y 99%. F. e. s. R. G. R. Bacon and H. A. O. Hill, Soc. 1964, 1108. 

The Sucholeiki thioether linkage can be synthesized via a disulfide bond (NpSSMpact) and addition of benzylbromide 408 or alternatively via the chlorine derivative and following reaction with benzylmercaptan. Other syntheses start from thiols that are converted with electrophiles. 

Jin Z, Xu B, Hammond GB. Green synthesis of vicinal dithioethers and alkenyl thioethers from the reaction of alkynes and thiols in water. Eur. J. Org. Chem. 2010 168-173. 

Pyrrolethiols, readily obtained from the corresponding thiocyanates by reduction or treatment with alkali, rapidly oxidize to the corresponding disulfides. They are converted into thioethers by reaction with alkyl halides in the presence of base. Both furan- and thiophene-thiols exist predominantly as such rather than in tautomeric thione forms. 

---