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

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.

Automated summary

For the first time, we have developed a one-step method for synthesizing substituted 3,4-dihydroquinolinones with an allomaltol moiety. The method involves acid-catalyzed recyclization of spiroindolinepyrano[3,2-b]pyrans, which are obtained through a multicomponent reaction of 3-hydroxy-4-pyranones, isatins, and malononitrile. This transformation is unique to 3-hydroxy-4-pyranone derivatives and not commonly observed in other heterocyclic enols. The advantages of this method include the use of easily accessible starting materials and a simple work-up procedure that eliminates the need for chromatographic purification. The structure of one of the synthesized products was determined by x-ray diffraction.