Preparation and Reactions of Sulfur Containing Substrates

A number of phase transfer reactions of sulfur containing substrates have been reported. These include substitution reactions in which sulfur is nucleophile, electrophile or an ancillary function. The synthesis of a variety of thioethers has been reported, as have the alkylation of numerous sulfur stabilized carbanions. In addition, reduction of both disulfides and N-tosylsulfilimines have been conducted under phase transfer catalytic conditions. The unifying theme of this chapter is, therefore, the synthesis and reactions of sulfur containing molecules. Inherent in this approach is some redundancy, but it is hoped that the ability to locate reactions of interest compensates. 

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Contents Introduction and Principles. - The Reaction of Dichlorocarbene With Olefins. - Reactions of Dichlorocarbene With Non-Olefinic Substrates. -Dibromocarbene and Other Carbenes. - Synthesis of Ethers. - Synthesis of Esters. - Reactions of Cyanide Ion. - Reactions of Superoxide Ions. - Reactions of Other Nucleophiles. - Alkylation Reactions. - Oxidation Reactions. - Reduction Techniques. - Preparation and Reactions of Sulfur Containing Substrates. -Ylids. - Altered Reactivity. - Addendum Recent Developments in Phase Transfer Catalysis. 

Preparation and Reactions of Sulfur Containing Substrates Table 13.2 (continued)... 

Thiol-, alkylthio-, and arylthio-quinazolines with the sulfur-containing substituent in the heterocyclic ring are prepared by the same sort of reactions as reviewed for pyrimidines. Sulfur functions in the carbocyclic ring are best introduced via the substrate used for ring formation. Thiation, by way of electrophilic substitution, for example by sulfonation reactions in the carbocyclic ring, is substituent dependent and may have to be carried out in a precursor before quinazoline ring formation. 

Previously, the synthesis of flve-membered heterocycles containing sulfur, selenium, and tellurium was reported by Sibor and Pazdera (1996). Two different kinds of heterocycles (93-95) can be prepared by the reaction of substrates (92), a chalcogen atom, and isothiocyanate or ketones in the presence of triethylamine under ultrasonic conditions (Scheme 8.29). Beyond the utilization of ultrasound, the authors studied the use of conventional conditions, as well as microwave irradiation. 

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