Efficient construction of diverse spiro[indoline-3,4′-pyrrolo[3,4-b]pyridines] via [3+3] cycloaddition of MBH carbonates of isatins with β-enamino maleimides

An efficient method to construct unique spiro[indoline-3,4 '-pyrrolo[3,4-b]pyridines] was successfully developed via a DABCO promoted formal [3 + 3] cycloaddition reaction of MBH carbonates of isatins with beta-enamino maleimides in acetonitrile at room temperature. This reaction afforded multifunctionalized spiro[indoline-3,4 '-pyrrolo[3,4-b]pyridines] and spiro[dipyrrolo[3,4-b:3 ',4 '-e]pyridine-8,3 '-indolines] in good yields and with lower diastereoselectivity. The relative configuration of the two diasteromers of the spiro compounds was clearly elucidated by the determination of eight single crystal structures.