Synthesis of 4,5-diaminopyrrolo[1,2-a]quinoline derivatives by annulation of N,N-dialkyl[2-(pyrrol-1-yl)benzylidene]ammonium salts in the presence of an isocyanide

Regioselective synthesis of 3-acylindolizines and benzo- analogues via 1,3-dipolar cycloadditions of N-ylides with maleic anhydride

3-Acylindolizines (5a-5f) and their benzo- analogues 1-acylpyrrolo[1,2-a]quinolines (6a-6f) and 1-acylpyrrolo[2,1-a]isoquinolines (7a-7i) are regioselectively synthesized by a convenient one pot reaction of the corresponding pyridinium (quinolinium, isoquinolinium) ylide with maleic anhydride (MA) in the presence of the mild oxidant tetrakispyridinecobalt(ii) dichromate (TPCD). These reactions proceed via a tandem reaction sequence of 1,3-dipolar cycloaddition of azomethine ylide with MA, anhydride hydrolysis and oxidative bisdecarboxylation of the primary cycloadducts followed by dehydrogenative aromatization of the dihydroindolizines. TPCD serves as both decarboxylation and dehydrogenation reagent in the reactions. These results show that TPCD is a promising new reagent for bisdecarboxylation of aliphatic carboxylates.

An interrupted Ugi reaction enables the preparation of substituted indoxyls and aminoindoles

In a variation of the classical Ugi reaction, an acid promoted reaction between imines and isocyanides forms both 3-aminoindoles and substituted indoxyls. A recently reported triflyl phosphoramide is shown to be critical to obtain high yields under mild conditions.