Hexamethyldisilathiane-Based Thionation of Carbonyl Compounds: A Versatile Approach to Sulfur-Containing Heterocycles

Reactions of hexamethyldisilathiane (HMDST) with carbonyl compounds under the catalytic activity of CoCl2·6H2O or trimethylsilyltriflate lead to a simple and general access to thioaldehydes and thioketones, which could be isolated as their cycloadducts with dienes. The use of CF3SO3SiMe3 in reactions with cyclohexadiene allows a stereopredetermined access to either the endo- or the exo-isomer. Furthermore, on using (beta)-silyl-substituted acetylenic ketones, a smooth access to acetylenic thioketones can be achieved. In reactions with aromatic and heteroaromatic o-azido aldehydes, the reactivity of HMDST may be finely tuned toward the synthesis of o-azido thioaldehydes, fused isothiazole ring systems, aromatic and heteroaromatic o-amino aldehydes, and o-amino thioaldehydes. HMDST proved also very efficient in thionating more intriguing substrates such as acylsilanes. Thus, thioacylsilanes, thioformylsilanes, unsaturated thioacylsilanes and -stannanes can be obtained in good yields. Ethylenic thioacylsilanes showed an interesting behavior leading to a general synthesis of functionalized dithiins. Finally, HMDST led also to the synthesis of bis (thioacylsilanes), which led to the formation of new silylated thiaheterocyclic systems. 1 Introduction 2 HMDST-Based Synthesis of Thiocarbonyl Compounds 2.1 Thioaldehydes and Thioketones 2.2 (alpha),(beta)-Unsaturated Thiocarbonyl Compounds 3 Tuning of the Chemical Behavior of Azido Aldehydes 3.1 Azido Thioaldehydes 3.2 Isothiazoles 3.3 Amino Aldehydes 3.4 Amino Thioaldehydes 4 Reactivity of Amino Thioaldehydes 5 Thioacylsilanes and Thioacylstannanes 5.1 Synthesis of Thioacylsilanes and Thioformylsilanes 5.2 (alpha),(beta)-Unsaturated Thioacylsilanes 5.3 (alpha),(beta)-Unsaturated Thioacylstannanes 5.4 Bis(thioacylsilanes) 6 Conclusions