INDOLE SYNTHESES WITH ORTHO-TOLYL ISOCYANIDE - 3-ACYLINDOLES AND 2-SUBSTITUTED INDOLES

In the preceding paper we described syntheses of some indole derivatives by elaboration of (lithiomethyl)phenyl isocyanide (1) with electrophiles such as alkyl halides, 1 al-kylene oxides, 1 and isocyanates, 2 followedby cyclization. Herein, we wish to report that acylation of the ortho methyl group of o-tolyl isocyanide can be best performed by treating (lithiomethyl) phenyl isocyanide (1) with allyl carboxylates and that o-(acylmethyl)phenyl isocyanides (2) thus prepared were readily converted to 3-acylindoles (3) and 2-alkyl(or2-aryl)indoles (4). Preparation of 3-acylindoles (3) and 2-substituted indoles (4) by the previous methods3-4 is not always satisfactory in respect to the yields and the reaction conditions. The present reaction provides a convenient synthetic method for preparation of 3-acylindoles and 2-alkyl(or 2-aryl)indoles starting with o-tolyl isocyanide, 5 which is readily prepared from commercially available o-toluidine. © 1979, American Chemical Society. All rights reserved.