One-pot, sequential four-component synthesis of benzo[c]pyrano[3,2-a]phenazine, bis-benzo[c]pyrano[3,2-a]phenazine and oxospiro benzo [c]pyrano[3,2-a]phenazine derivatives using 1,4-diazabicyclo[2.2.2]octane (DABCO) as an efficient and reusable solid base catalyst

1,4-Diazabicyclo[2.2.2]octane (DABCO) has been used as an efficient and reusable solid base catalyst for the one-pot, two-step, four-component synthesis of pyrano[3,2-a]phenazine derivatives by the condensation reaction of 2-hydroxy-1,4-naphthoquinone, 1,2-diamines, carbonyl compounds and alkylmalonates under conventional heating as well as microwave irradiation. This procedure has also been applied successfully for the synthesis of novel bis- benzo[c]pyrano[3,2-a]phenazine and oxospiro benzo[c]pyrano[3,2-a]phenazine derivatives. Using this procedure, all the products were obtained in good to excellent yields. The catalyst has been recovered and reused several times without any loss of reactivity.