“…[10] However, reacting 4 with 1 equivalent of Et 3 N and 2 equivalents of styrene 6a, as suitable trapping electron-rich dienophile, in CHCl 3 at 60 8C, i.e., under the reaction conditions that we found to be effective for the generation of o-imonothioquinones, [5] no reaction occurred and the starting diselenide 4 was recovered almost quantitatively after an acid work-up. Thus, although the pK a values indicated that the selenolate ion should be a better leaving group than the phthalimide anion, the Se À Se bond in 4 was not broken under the reaction conditions tested.…”