Quantification of the electrophilicities of dithiocarbenium ions

The reactions of the dithio substituted carbenium ions 2a-c with allylsilanes, allylstannanes (3), and silylated enol ethers (4) which yield dithioacetal protected beta,gamma-unsaturated carbonyl compounds (7) and selectively protected 1,3-dicarbonyl compounds (8), have been studied kinetically. The second-order rate constants have been used to determine the electrophilicity parameters for the [1,3]dithiolan-2-ylium ion 2a (E = -6.25) and the [1,3]dithian-2-ylium ions 2b (E = -6.82) and 2c (E = -2.17). It is shown how these parameters can be used to predict the electrophilic potential of 2a-c.