Continuous-flow Fe-zeolite-catalyzed temperature-directed synthesis of bioactive tetraketones and xanthenes using epoxides and cyclic-1,3-diketones via a Meinwald rearrangement

Abstract

An environmentally benign approach for bioactive tetraketones using epoxides and cyclic-1,3-diketones in the presence of Fe-zeolite as a catalyst via a Meinwald rearrangement was developed under batch and continuous flow modes. Further increasing the temperature to 180 °C, these tetraketones underwent a cyclization reaction in the presence of catalytic Fe-zeolite to afford xanthene derivatives. Moreover, this Fe-zeolite catalyst was also used for the reaction of aldehyde and cyclic 1,3-diketone, affording the tetraketone in a high yield. Advantageously, the present approach enables gram-scale synthesis in batches as well as in continuous flow. This approach can sustainably generate many bioactive tetraketones and xanthenes as it does not produce any waste. The Fe-zeolite used in this process is easy to synthesize in the multigram scale, inexpensive, easy to recover, and recyclable.