BF3 etherate-mediated microwave-assisted facile synthesis of thiopyrano[2,3-b]indol-2-one

A facile synthesis of indole annulated 2H-thiopyran-2-ones has been developed by condensation of indoline-2-thiones with acetoacetic esters in the presence of borontrifluoride etherate (BF3 etherate) using microwave irradiation. This one-step operationally simple methodology leads to thiopyrano[2,3-b]indol-2-ones in good yields.