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The reaction of unsubstituted indole with different acylating agents such as acid chlorides, anhydrides, nitriles, and amino acid derivatives in the presence of Lewis acid is reported.The synthesis of 3-acylindoles has been the subject of considerable interest not only because they are used as synthetic intermediates in alkaloid synthesis but also because they have biological activities. 1 Three major synthetic methods have been employed to prepare this class of compounds using indole as the starting material: (1) acylation of indole Grignard reagents, [2][3][4] (2) acylation of N-protected indoles, 5 and (3) the Vilsmeier-Haack reaction. 2 There are also other methods based on acyl cation equivalents such as nitrilium salts 6 and dialkyl carbenium ions. 7,8 Another method, using N-(R-haloacyl)pyridinium salts, gives predominantly 3-acylindoles under controlled conditions, but it seems to be restricted to some very reactive R-haloacyl halides. 9 Each of these methodologies has merits and shortcomings that limit their scope and yield.

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Regioselective Acylations at the 2 and 6 Position of N-Acetylindole.-Preformation of an AlCl 3 -complex of 1-acetylindole (I) allows a selective acylation in the 6-position. On the other hand, addition of (I) to a mixture of bis acid chlorides (V) and AlCl 3 leads to 2-acylated products selectively. -(CRUZ, ROSIMEIRE P. A.; OTTONI, OLIVIA; ABELLA, CARLOS A. M.; AQUINO, LIGIA B..; Tetrahedron Lett. 42 (2001) 8,