3,7-二硝基二苯并环状卤鎓盐在碱性条件下的反应机理研究

Study on the Reaction Mechanism of 3,7-Dinitrodibenzohalonium Salts under Basic Conditions

研究了 3 ,7 二硝基二苯并溴五环盐 ( 1a)与一些伯胺及仲胺的反应 ,其主要产物 6( 2 溴 2′ 烷氨基 4,4′ 二硝基联苯 )与次要产物 7( 2 溴 3′ 烷氨基 4,4′ 二硝基联苯 )互为位置异构体 ,这一结果支持一个以苯炔类化合物 ( 4 )为中间体的反应机理 .进而用蒽成功地捕获了一系列 3 ,7 二硝基二苯并环状卤盐 ( 1a～ 1c)在碱性条件下形成的苯炔类中间体 。

Reactions of 3,7-dinitrodibenzobromolium salt (1a) with primary and secondary amines were studied. The result that the major products 6a similar to 6e (2-bromo-2'-alkylamino-4,4'-dinitrobiphenyl) and the minor products 7a similar to 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 similar to 1c) under basic conditions were successfully trapped using anthracene. The structures of the trapped products 8a similar to 8c were established by H-1 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 77degrees, showing that 8a is an axial-chiral molecule.