in dichloromethane Fp(dimethyldioxene)(BF4), Et4NCN and CH2Cl2 are combined at 0°C under Ar, stirring (0.5 h).; Addn. of ether pptd. Et4NBF4. Filtration of mixt. through Al2O3, washing of Al2O3 with ether, evapn. of solvents in vac., elem. anal.;