Acid‐Promoted Hetero Annulation: An Expeditious Route to Construct Functionalized Pyrido‐ and Pyrimido[5′,4′:5,6]pyrido‐ Fused [a]Carbazoles

Abstract

A transition metal-free multicomponent coupling of 2-arylidene/heteroarylidene carbazole with alkyne and nitrile in the presence of Lewis acid BF 3 .OEt 2 is described. This method was proven to be usable for the preparation of library of Nacetylated pyrido[3,4-a]carbazoles. Conversely, p-toluenesulfonic acid-catalyzed hetero annulation of uracil with 2-arylidene carbazole afforded novel aromatic pyrimido[5',4':5,6]pyrido[2,3-a]carbazoles in isolated yields of up to 82 % in solid-state manner. The structures of the synthesized heterocycles were confirmed by elemental analysis and spectral data. The salient features of these one-pot methods are rapid formation of products with moderate to good yields, readily accessible reactants and involve less hazardous chemical techniques.