Charge control in the SNAr reaction. Meta substitution with respect to the activating nitro group in 3,4-dihalogenonitrobenzenes
作者:Maria Cervera、Jordi Marquet、Xavier Martín
DOI:10.1016/0040-4020(95)01073-4
日期:1996.2
The reactions of 3-fluoro-4-chloronitrobenzene and of 3,5-difluoro-4-chloronitrobenzene with thiophenoxide anion lead to predominant substitution of the chlorine atom through SNAr orbital-controlled processes. However, when harder nucleophiles (methoxide anion) are used, the substitution of a fluorine atom meta with respect to the activating nitro group becomes apparent in the reaction of 3-fluoro
3-氟-4-氯硝基苯和3,5-二氟-4-氯硝基苯与噻吩氧化物阴离子的反应导致氯原子主要通过S N Ar轨道控制过程取代。然而,当使用较硬的亲核试剂(甲醇根阴离子)时,相对于活化硝基而言,氟原子间位的取代在3-氟-4-氯硝基苯的反应中是明显的,而3-氟-4-氯硝基苯的反应主要是5-氟-4的反应。 -氯-3-甲氧基硝基苯,几乎不参与3,5-二氟-4-氯硝基苯的反应。动力学测量和理论计算表明,观察到的氟原子的间位取代是S NAr电荷控制的反应,具有松散结合的过渡态。