in ethanol under N2; mixt. of B compd. and CsF (molar ratio 1:3) in EtOH stirred under reflux for 25 h; cooled to room temp.; dried in vac. by rotary evaporator; dissolved in acetone; filtered by glass frit; washed with acetone; solvent removed from filtrate in vac.; recrystd. from H2O; elem. anal.;

in ethanol under N2; mixt. of B compd. and CsF (molar ratio 1:3) in EtOH stirred under reflux for 25 h; cooled to room temp.; dried in vac. by rotary evaporator; dissolved in acetone; filtered by glass frit; washed with acetone; solvent removed from filtrate in vac.; recrystd. from H2O; elem. anal.;