Indole derivatives.

Acylation of Indole under Friedel−Crafts ConditionsAn Improved Method To Obtain 3-Acylindoles Regioselectively

“…Nevertheless, troublesome protection-deprotection steps are necessary in such situations. 11,12 Additionally, the Vilsmeier-Haack reaction, involving amides and POCl 3 , is not always effective, 3,13,14 providing only moderate yields and requiring the preparation of the amide if it is not commercially available. Herein we describe a Friedel-Crafts-type acylation of unsubstituted indole, through a very easy method that gives 3-acylindoles regioselectively and in high yields without laborious workups.…”

“…The use of N-protecting groups is generally the chosen strategy to overcome the concurrent formation of 1-acyl derivatives and to limit polymerization, which has not been observed when the indole system is deactivated by the presence of electron-withdrawing groups on the ring. Nevertheless, troublesome protection−deprotection steps are necessary in such situations. , Additionally, the Vilsmeier−Haack reaction, involving amides and POCl 3 , is not always effective, ,, providing only moderate yields and requiring the preparation of the amide if it is not commercially available.…”