The first N,N′-ditosyl-substituted cyclic boron cation, stabilized by neighboring-group participation by two sulfonyl groups, and the alternative, stabilized by polar solvents

When 2-bromo-1,3-ditosyl-1,3,2-diazaborolidine was treated with AgSbF6, a novel cyclic boron cation was formed in CD2Cl2, the 11B NMR chemical shift of which appeared at 8.7 ppm. Ab initio calculations were consistent with the cationic boron center being stabilized by neighboring-group participation of the two sulfonyl functions. The reaction in CD3NO2 resulted in an alternate formation of a cyclic boron cation species (16.2 ppm), stabilized by coordination to the basic solvents.