The S-alkylated indolyloxadiazoles 2a-l were obtained regioselectively by alkylation of 5-(1H-indol-2-yl)- 1,3,4-oxadiazole-2(3H)-thione 1, using TEA as acid scavenger. Alkylation of 1 with 1-bromopropane, 1-bromobutane, 1- bromoundecan, in the presence of K2CO3, yielded the N-alkylated products 3i-j,m in addition to the S-alkylated analogs 2i-j,m. A facile thio-aza-Claisen rearrangement (S??N allylic rearrangement) of the S-allyl-oxadiazole 2k to the N-allyl analog 3k was achieved in excellent yield. Further allylation of 2k and 3k in the presence of K2CO3 led to allylation of the NH indole ring producing 5 and 6, respectively. Benzylation of 1 in the presence of K2CO3 yielded 7 which resisted the S→N migration of the benzyl group. The 1H NMR, 13C NMR and mass spectra confirmed the structures and differentiated between the N- and S-alkylated products.
通过使用
三乙胺(
TEA)作为酸捕获剂,5-(1H-
吲哚-2-基)-
1,3,4-噁二唑-2(3H)-
硫酮1的烷基化反应,区域选择性地合成了S-烷基化的
吲哚噁二唑2a-l。1与
溴丙烷、
溴丁烷、
溴十一烷在
碳酸钾存在下反应,除了生成S-烷基化类似物2i-j,m外,还生成了N-烷基化产物3i-j,m。S-烯丙基噁二唑2k通过简便的
硫-氮-Claisen重排(S→N烯丙基重排),以优异的产率转化为N-烯丙基类似物3k。进一步在
碳酸钾存在下对2k和3k进行烯丙基化反应,分别产生
吲哚环NH的烯丙基化产物5和6。在
碳酸钾存在下,1的苄基化反应生成了7,且苄基未发生S→N迁移。1H NMR、13C NMR和质谱证实了结构,并区分了N-和S-烷基化产物。