Dibenzo-1,5-diazocine-2,6-dione, 2-iminoindolin-3-one and N-(carbamoylmethyl)-aminobenzoic acid ester from aminobenzoic acid by multicomponent reactions

Aminobenzoic acids show different types of multicomponent reactions when treated with a carbonylic component and an isocyanide in an alcoholic solution. Anthranilic acid provides dibenzo-1,5-diazocine-2,6-dione derivatives by a double Ugi four component reaction (\-4CR) or depending on the reaction conditions the U-5C-4CR product, a N-(carbamoylmethyl)anthranilic acid ester. Whereas anthranilic acid reacts hardly with ketones in that kind of multicomponent reaction Instead the preferred reaction with isocyanides is the formation of 2-iminoindolin-3-ones. While 3-aminobenzoic acid shows no reaction, 4-aminobenzoic acid forms the U-5C-4CR product exclusively. (C) 1998 Elsevier Science Ltd. All rights reserved.