A novel method for the preparation of indole derivatives that are alkoxy- and hydroxy-substituted in the benzene portion of the indole nucleus is described. The acid-induced cyclization reaction of (arylsulfonyl)pyrrole derivatives (4a, 5b, and 5a) in the presence of an appropriate alcohol gave 4-, 5-, 6-, and 7-alkoxyindole derivatives (13 and 28), respectively, where the alkoxy group was originated from the alcohol employed. As an application of the present method, a short and efficient synthesis of two dopamine agonists (34 and 44) was attained by treating appropriately functionalized pyrrole derivatives (38 and 41) with an acid in the presence of 1, 3-propanediol, followed by deprotection of alkoxy function, and subsequent reduction with lithium aluminum hydride. A reaction mechanism is also suggested for the formation of an unusual product, 4-[2-(diprophlamino)-1-hydroyethyl]-6-hydroxyindole (46) in the reduction of N, N-dipropyl-(6-hydroxy-1-phenylsulfonyl)indole-4-acetamide (40).
本文介绍了一种制备
吲哚核的苯部分被烷氧基和羟基取代的
吲哚衍
生物的新方法。(芳基磺酰基)
吡咯衍
生物(4a、5b 和 5a)在适当的醇存在下发生酸诱导环化反应,分别得到 4、5、6 和 7-烷氧基
吲哚衍
生物(13 和 28),其中的烷氧基来自所使用的醇。本方法的一个应用是,在 1,3-
丙二醇存在下,用酸处理适当官能化的
吡咯衍
生物(38 和 41),然后脱去烷氧基,再用
氢化铝锂还原,从而简短高效地合成了两种
多巴胺激动剂(34 和 44)。在还原 N,N-二丙基-(6-羟基-1-苯磺酰基)
吲哚-4-乙酰胺(40)的过程中,还提出了一种不常见产物 4-[2-(二rophlamino)-1-羟乙基]-
6-羟基吲哚(46)的生成反应机理。