Thiopyran-2-thiones synthesis

The synthesis of the thiathiophthens (13) from 4ZT-thiopyran-4-thiones (11), involving ring opening with sodium sulphide and oxidation of the resulting dianion (12) with ferricyanide, has been described in detail. The method provides a convenient route to the parent compound and succeeds with the symmetrically substituted thiopyrans (11 = Ph,... 

Details have been given for the synthesis of 6a-thiathiophthens (see Chapter 8) from 4 -thiopyran-4-thiones. Analogous reactions with 4H-thiopyran-4-selenones lead to 6a-selenathiophthens. ... 

In an attempt to synthesize a thiochalcone by the reaction of 3-(NN-di-ethylamino)-l-(p-methoxyphenyl)propene-l-thione with phenyl magnesium bromide, in an ogy with a well-known synthesis of chalcones, Quiniou and his co-workers obtained instead the thiopyran (88), a formal dimer of the thiochalcone expected." The thiirans (89) were formed by the reaction of... 

Many further examples have been given of the preparation of mixtures of thiopyrylium salts and the corresponding tetrahydrothiopyrans, by the action of hydrogen sulphide and various acids on 1,5-diketones. Selenopyrylium salts have also been prepared by this method. 2-Amino-6-methylthio-thiopyrylium salts, obtained by methylation of the related 2H-thiopyran-2-thiones, react with aromatic amines to give 2-arylimines (42). 2-Amino-6-arylthiopyrylium salts have also been prepared, from 3-mercaptovinylacrylonitriles, by an extension of a reaction previously used for the synthesis of 2-aminopyrylium and pyridinium salts. Several theoretical treatments have appeared. Non-empirical calculations suggest that the 3d orbitals are used only to a trivial extent," but, in another study, the conclusion is reached that involvement of the d-orbitals may be important, and that contributions of forms of type (43) to the hybrid... 

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