Et3N as a catalyst for the synthesis of indeno[1,2-b]chromene derivatives via three-component condensation reaction

Functionalized indeno[1,2-b]chromene derivatives have been synthesized via condensation reaction of 1H-indene-1,3(2H)-dione with benzaldehyde and cyclization with 2-hydroxynaphthalene-1,4-dione in the presence of a catalytic amount of triethylamine (Et3N) in EtOH at room temperature. It was observed that benzaldehyde bearing electron donating group gave high yield of product, whereas, benzaldehyde having electronic withdrawing substituent does not participate in this reaction. The structures were confirmed spectroscopically (IR, 1H- and 13C-NMR, and Mass). A plausible mechanism for this reaction is proposed (Scheme 2). Good yields and easy purification are the main advantages of the present method. Products of these reactions have structural similarity to naturally occurring pyranokunthone B, lambertellin, β-lapachone, and α-xiloidone.