31485-43-5Relevant academic research and scientific papers
Synthetic Studies on Indoles and Related Compounds. XV. An Unusual Acylation of Ethyl Indole-2-Carboxylate in the Friedel-Crafts Acylation
Murakami, Yasuoki,Tani, Masanobu,Tanaka, Kenjiro,Yokoyama, Yuusaku
, p. 2023 - 2035 (2007/10/02)
The Friedel-Crafts reaction of ethyl indole-2-carboxylate (1a) with acyl chlorides or acid anhydrides in the presence of Lewis acids was investigated in order to establish a preparative procedure for the corresponding ethyl 3-acylindole-2-carboxylates (4).Although monoacylation occured successfully, the products were generally a mixture of ethyl 3-, 5-, and 7-acylindole-2-carboxylates (4,5 and 6).The ratio of the yields of these three products varied greatly depending on reaction conditions and reagents used.A tendency that the 3-acylindole (4) was obtained as a main product was observed when a Lewis acid other than aluminum chloride was used as a catalyst and/or an acyl chloride derived from a weaker acid was employed, whereas a tendency for formation of the 5- and 7-acylindoles (5 and 6) was observed when aluminum chloride and/or an acyl chloride derived from a stronger acid was used.As to the 5- and 7-acylindoles (5 and 6) , the yields of the former were always much higher than those of the latter (6).The result indicates that ethyl 3- and 5-acylindole-2-carboxylates can be regioselectively prepared from a common substrate (1a) by changing the reaction conditions or reagents. friedel-craft acylation; ethyl indole-2-carboxylate; acyl chloride; acid anhydride; lewis acid; aluminum chloride; acylindole
