Electrostatic Activation of Nucleofuges: Cationic Leaving Groups

The substitution of two chlorine atoms by dimethylaminopyridino groups in PCl 3 ( 1 ), MeOPCl 2 ( 2 ), and MeOP(O)Cl 2 ( 3 ) yields phosphorus derivatives that are dicationic ( 1 and 2 ) or monocationic (3) . These molecules are highly activated toward nucleophilic attack. For the first time, in nucleophilic reactions a cationic group is the leaving group. In fact, the nucleofuge derived from 3 is a better leaving group than the trifluoromethane sulfonate ion.