Facile synthesis of indolizino[8,7-b]indole and pyrido[1,2-a:3,4-b’]diindole derivatives based on domino reactions of 1-aroyl-3,4-dihydro-β-carbolines

A convenient approach to the synthesis of 1-aroyl-3,4-dihydro-β-carbolines via Pictet–Spengler reaction has been developed. A variety of reagents, such as unsaturated aldehydes, ketones, maleic anhydride in the construction of functionally diverse indolizino[8,7-b]indole, and pyrido[1,2-a:3,4-b']diindole derivatives has been used. The developed method is a simple and convenient procedure giving medium and excellent yields, showing a wide functional group tolerance.