pyridine in dichloromethane byproducts: Cl3BNC5H5; condensation of BCl3 to soln. of (tmp)2BF in CH2Cl2 under stirring (N2,strict avoidance of moisture, -40°C), refluxed (room temp., dry ice cooler), evapn. (vac.), addn. of pyridine, refluxed (2 h); evapn. (vac.), refluxed in hexane (1 h), filtration (Cl3BNC5H5), distn.; elem. anal.;