CHEMISTRY OF SILYL THIOKETONES .7. SYNTHESIS, CYCLOADDITION AND OXIDATION OF CYCLOALKYL SILYL THIOKETONES AND DESILYLATION OF THE REACTION-PRODUCTS

Cycloalkyl silyl thioketones 3, achiral as well as chiral at carbon, h ave been synthesized by thionation of the corresponding acyl silanes 2 . During thionation of 2a, 2d and 2f unexpected products were observed . Cycloaddition reactions of cycloalkyl silyl thioketones 3 with buta- 1,3-diene have been performed. A diastereoisomeric excess (d.e.) of 80 % was obtained in the case of chiral thione 3e. Desilylation of the cy cloadducts was only possible at the stage of the corresponding alpha-s ilyl sulfones 11. Oxidation of compounds 3 led to the corresponding (E )-silyl sulfines 13 which by stereospecific fluorodesilylation gave (Z )-thioaldehyde S-oxides 14. Compound 14e is the first example of enant iomerically pure mono-substituted sulfine (thioaldehyde S-oxide).