Synthesis of organic compounds using some natural compounds as catalysts has gained more attention in recent decades. With respect to the importance of these procedures, the synthesis of 3,4-dihydropyrano[2,3-c]chromene and pyrano[2,3-d]pyrimidine derivatives using vitamin B12 by a one-pot reaction of malononitrile, benzaldehydes and 4-hydroxycumarine or 1,3-dimethylbarbituric acid is reported.
