Functions with Two Chalcogens Other Than Oxygen

Synthetic methods for dithioic acid salts and esters developed since the 1990s have been introduced. The reaction of organometallic reagents with CS2 has been applied to the synthesis of dithioic acid metal salts. Efficient synthetic reactions leading to inner salts of dithioic acid have been reported. The alkylation led to the corresponding esters. The 1,1-dihaloalkyl sulfides and thioic acid S-esters and thioamides are converted into dithioic acid esters with ZnS, Lawesson'′s reagent, P4S10, and H2S. A variety of α-oxo, β-oxo, and α-sulfonyldithioic acid esters have been synthesized. The highly stereoselective synthesis of these derivatives was achieved by utilizing the thio-Claisen rearrangement. Synthetic examples of dithioic acid derivatives where heavier typical elements such as Si, Ge, Sn, Pb, P, As, S, and Br are attached to the sulfur atom are also shown. A wide variety of synthetic methods for selenothioic acid S-esters have been established. Selenothioacetic acid S-esters were the key starting materials for the synthesis of selenothioic acid esters. Allylation of selenothioacetic acid S-esters gave γ,δ-unsaturated S-esters. Di- and triallylation of the esters were carried out selectively. Aldol condensation reaction of the esters leads to β-hydroxyselenothioic acid S-esters. Finally, the first examples of selenothioic and diselenoic acid salts have been described.