Acid‐catalyzed recyclization of spiroindolinepyrano[3,2‐b]pyrans to 3,4‐dihydroquinolinone derivatives containing allomaltol fragment

Abstract

For the first time, we developed a novel one‐step method for the synthesis of substituted 3,4‐dihydroquinolinones with allomaltol moiety. The suggested approach includes acid‐catalyzed recyclization of spiroindolinepyrano[3,2‐b]pyrans which can be obtained by multicomponent reaction of 3‐hydroxy‐4‐pyranones, isatins and malononitrile. The described transformation is a distinctive feature of 3‐hydroxy‐4‐pyranone derivatives and is not typical for other heterocyclic enols. The advantages of the considered method are the employment of easily accessible starting materials and simple work‐up procedure which can avoid chromatographic purification. The structure of one of synthesized products was determined by x‐ray diffraction.