Reactions of 3,7 dinitrodibenzobromolium salt (1a) with primary and secondary amines were studied.The result that the major products 6a～6e (2 bromo 2' alkylamino 4,4' dinitrobiphenyl) and the minor products 7a～7e (2 bromo 3' alkylamino 4,4' dinitrobiphenyl) are regioisomers supports a mechanism with the substituted benzyne 4 as the intermediate.It provides powerful backing for this mechanism that the formed benzyne intermediates of some 3,7 dinitrodibenzohalonium salts (1a～1c) under basic conditions were successfully trapped using anthracene.The structures of the trapped products 8a～8c were established by 1H NMR, MS and IR spectroscopy.The crystal and molecular structure of 8a was determined by X ray analysis.The dihedral angle between two phenyl rings of the biphenyl part of 8a is 77°, showing that 8a is an axial chiral molecule.

Key words: 3,7-dinitrodibenzohalonium salt, amine, anthracene, benzyne, trap, reaction mechanism