THE GENERATION AND SYNTHETIC APPLICATIONS OF EPISULFONE ALPHA-ANIONS

Treatment of the episulfone, ,8-dimethyl-2,3-epithio-6,10-dioxaspiro[4 .5]decane S,S-dioxide 1, with lithium diisopropylamide to generate the corresponding alpha-sulfonyl anion, and anion trapping with trimethyl silyl chloride or trimethylstannyl chloride in situ, produced the corr esponding monosilyl, disilyl, monostannyl and distannyl episulfones as relatively stable, fully characterised crystalline solids. The struct ure of the disilylated episulfone 3a was also confirmed by X-ray cryst allography: this is the first reported X-ray structure of a tetrasubst ituted episulfone and the long carbon-carbon episulfone bond length (1 .686 Angstrom) is particularly noteworthy. With similar procedures the monotriethylsilyl, monotributylstannyl, and the triethyl, trimethyl d isilyl adducts were prepared in reasonable to good yields. On treatmen t with potassium tert-butoxide or thermolysis the functionalized episu lfones lost sulfur dioxide to produce the corresponding vinyl-silanes and -stannanes. Attempts to use carbon electrophiles for alpha-sulfony l anion trapping are also reported. The monobenzoylated adducts 9 and 10 were obtained by in situ trapping with benzoyl chloride. In additio n, it was found that treatment of the disilylated episulfone 3a with c aesium fluoride-benzaldehyde gave the monoalkylated adduct 11, albeit in low yield, Other reactions of the silylated/stannylated episulfones are also reported.