An efficient cascade reaction for the synthesis of oxazino[4,3-a]indoles and pyrano[3,4-b]indoles from vinyl selenones

Indole derivatives represent a common structural motif in diverse naturally occurring alkaloids and pharmaceutical or agrochemical products. In recent years vinyl selenones have been identified as valuable and versatile substrates to effect economical and environmentally friendly cascade reaction. Herein we describe a Michael initiated ring closure sequence to synthesize in one pot oxazino[4,3-a]indoles and pyrano[3,4-b]indoles starting from vinyl selenones and (1H-indol-2yl)methanols in presence of potassium hydroxide. Structural variations of both substrates were well tolerated and furnished the corresponding fused indoles in good yields.