Neighboring group effect of pyridazine and pyrazine rings for π-facial selectivity in the reactions of fused isopropylidenenorbornene systems with electrophilic reagents
作者:Tomoshige Kobayashi、Kiyomi Miki、Behrooz Nikaeen、Akira Ohta
DOI:10.1039/b101330k
日期:——
the electrophilic reactions with 4-phenyl-1,2,4-triazole-3,5(4H)-dione (PTAD), m-chloroperbenzoic acid (MCPBA) and N-bromosuccinimide (NBS) has been investigated. The ene reactions with PTAD exhibited exclusive syn selectivity to the heteroaromatic rings except for an isopropylidenenorbornene fused with a pyridazine N-oxide ring. The epoxidations with MCPBA and the ene reactions with NBS afforded mixtures
一系列的 哒嗪- 和 吡嗪合成了稠合的异亚丙基降冰片烯,并与4-苯基-1,2,4-三唑-3,5(4 H)-二酮(PTAD)进行了亲电反应的π面选择性,间氯过苯甲酸 (MCPBA)和 N-溴琥珀酰亚胺(NBS)已被调查。与PTAD的烯反应对杂芳环表现出唯一的顺式选择性,除了与吡啶嗪N-氧化物环稠合的异亚丙基降冰片烯。根据杂芳族环和取代基,用MCPBA进行的环氧化反应和与NBS的烯反应得到了顺式异构体和反式异构体的混合物。与a相比,主要的syn选择性苯稠合的同类物可归因于杂芳环上存在强的正静电势场,以通过静电相互作用来稳定极性过渡态。