The cyclization of methyl (E)-6-oxo-6-[1-(phenylsulfonyl)-1H-pyrrol-3-yl]-2-hexenoate (8a) using an equimolar amount of palladium chloride gave methyl 4-hydroxy-1-(phenylsulfonyl)-1H-indole-7-acetate (11a) in 33% yield. The similar cyclization of methyl (E)-6-acetoxy-6-[1-(phenylsulfonyl)-1H-pyrrol-3-yl]-2-hexenoate (8c) proceeded smoothly to give methyl 1-(phenylsulfonyl)-1H-indole-7-acetate (11c) and 4-acetoxy-7-methyoxycarbonylmethylidene-1-phenylsulfonyl-4, 5, 6, 7-tetrahydro-1H-indole (10c) in 41% and 22% yields, respectively. Conversion of the tetrahydroindole (10c) to the indole (11c) was accomplished in 44% yield by treatment with p-toluenesulfonic acid in benzene. Methyl (E)-6-[1-(phenylsulfonyl)-1H-pyrrol-3-yl]-2-hexenoate (8d) gave 11c and 7-methoxycarbonylmethylidene-1-phenylsulfonyl-4, 5, 6, 7-tetrahydro-1H-indole (10d) in 27% and 40% yields, respectively. The cyclization of ethyl (E)-4-(5-methoxycarbonyl-4-pentenyl)-1H-pyrrole-2-carboxylate (18) also gave the corresponding indole-7-acetate (20) and 7-methoxycarbonylmethylidene-4, 5, 6, 7-tetrahydro-1H-indole (21) in 16% and 49% yields, respectively.
使用等摩尔量的
氯化钯对(E)-6-氧代-6-[1-(苯磺酰基)-1H-
吡咯-3-基]-
2-己烯酸甲酯(8a)进行环化,得到
4-羟基-1-(苯磺酰基)-
1H-吲哚-7-乙酸甲酯(11a),产率为 33%。(E)-6-乙酰氧基-6-[1-(苯磺酰基)-1H-
吡咯-3-基]-
2-己烯酸甲酯(8c)的类似环化顺利进行,得到 1-(苯磺酰基)-
1H-吲哚-7-乙酸甲酯(11c)和 4-乙酰氧基-7-甲氧羰基亚甲基-1-苯磺酰基-4、5,6,7-四氢-1H-
吲哚(10c),收率分别为 41%和 22%。用
对甲苯磺酸在苯中进行处理,可将四氢
吲哚(10c)转化为
吲哚(11c),收率为 44%。(E)-6-[1-(苯磺酰基)-1H-
吡咯-3-基]-
2-己烯酸甲酯(8d)得到 11c 和 7-甲氧羰基亚甲基-1-苯磺酰基-4,5,6,7-四氢-1H-
吲哚(10d),收率分别为 27%和 40%。(E)-4-(5-甲氧羰基-4-
戊烯基)-1H-
吡咯-2-
甲酸乙酯(18)的环化反应也得到了相应的
吲哚-7-
乙酸酯(20)和 7-甲氧羰基亚甲基-4,5,6,7-四氢-1H-
吲哚(21),收率分别为 16%和 49%。