Novel and Simple Methodology for the Synthesis of 3-Acetylindoles and their N-Alkyl Derivatives Using TBAB as Phase Transfer Catalyst

Using 5% aq. NaOH, a simple method for the transformation of 3-cyanoacetylindoles 2(a-e) into 3- acetylindoles 3 (a-e), in good yields, is reported. Tetrabutylammoniumbromide (TBAB) is found to be an efficient phase transfer catalyst for the synthesis of N-alkyl derivatives 5(a-t) of 3-acetylindoles 3(a-e) giving products in excellent yields. 2 (a-e) were themselves obtained from simple indoles 1 (a-e) by reaction with cyano acetic acid in the presence of propionic anhydride at 100 °C for 5-10 min. Partial hydrolysis of 2 (a-e) under hot acidic conditions yielded the corresponding carboxamides α-(3-indolecarboxoyl)acetamides 4(a-e). Which could be readily transformed into the respective 3(a-e) by refluxing with 5% aq. NaOH for 2-2.5 h.