Nucleophilicity vs basicity in the reaction of sodium tert-butoxide with β-stannyl ketones

The reaction of 3-stannyl-1,2,3-triphenyl- and 3-stannyl-1,3-diphenyl-2-methylpropanones with sodium tert-butoxide in either t-BuOH or dimethyl sulfoxide (DMSO) as solvent Leads to Elimination and/or substitution products. The composition of the product mixtures depends essentially on the nature of the ligands attached to the tin atom, on the solvent, and also on the nature of the substituent on C-2. Thus, beta-(triphenyl), beta-(bromodiphenyl), and beta-(trichlorostannyl) ketones under go an exclusive elimination reaction Leading to an unsaturated Ketone in good to high yields (72%-96% both in t-BuOH and in DMSO. In the latter the reactions lead to higher yields in shorter times. On the other hand, beta -trimethylstannyl) ketones lead to mixtures of olefins and substitution products in t-BuOH and exclusively to substitution products in DMSO (96%-98%). Stereochemical results suggest that the elimination reactions proceed through an (E1cB)R mechanism.