Reactive, dicationic electrophiles: electrophilic activation involving the phosphonium group

In the following letter, we report our studies of dicationic electrophiles involving the phosphonium group and we present evidence that the cationic phosphonium group may dramatically enhance the reactivities of adjacent electrophilic centers. We describe superacid-catalyzed reactions involving phosphonium-substituted aldehydes, ketones, olefins, and alkynes, and their conversions to products of condensation and addition reactions. We also report the direct observation of a phosphonium-carboxonium dication in FSO3H-SbF5-SO2ClF by low-temperature C-13 NMR spectroscopy. (C) 2002 Elsevier Science Ltd. All rights reserved.