Alkylatlon orientation rules in conjugate addition of grignard reagents to nitropyrrole and nitrothiophene systems
作者:Roberto Ballini、Giuseppe Bartoli、Marcella Bosco、Renato Dalpozzo、Enrico Marcantoni
DOI:10.1016/s0040-4020(01)89831-8
日期:——
Conjugate addition of various Grignard reagents to 1-alkyl-2-nitropyrroles and to 2-nitrothiophene has been investigated. 1-Alkyl-2-nitropyrroles undergo alkylation at 3 and 5 positions with prevalence of the latter isomer. On the contrary, in 2-nitrothiophene system, formation of the 3-isomer prevails. In both systems, a bulkier Grignard reagent favours the 5-isomer formation. This trend can be reversed
已经研究了将各种格氏试剂偶联到1-烷基-2-硝基吡咯和2-硝基噻吩上的方法。1-烷基-2-硝基吡咯在3和5位发生烷基化,后一种异构体普遍存在。相反,在2-硝基噻吩系统中,形成了3-异构体。在两种体系中,较大的格利雅试剂都有利于5-异构体的形成。这种趋势可以逆转,由2-硝基吡咯的1-取代基增加空间位阻。1-(三异丙基甲硅烷基)-3-硝基吡咯和3-硝基噻吩仅产生2-异构体。该反应允许通过一锅法而不是经典的多阶段反应来合成2-烷基-3-硝基噻吩和吡咯。