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, have 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 cycloadducts was only possible at the stage of the corresponding alpha-silyl 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 enantiomerically pure mono-substituted sulfine (thioaldehyde S-oxide).