A new [4 + 1]/[4 + 2]bicycliaztion strategy for accessing functionalized indeno[1,2-b]pyran-2-ones

Abstract

A new base-promoted bicyclization strategy for the synthesis of functionalized indeno[1,2-b]pyran-2-ones has been established from readily accessible o-phthalaldehydes (OPA) and the preformed 1-arylethylidenemalononitriles. The reaction pathway involves an aldol addition, 5-exo-trig carbocyclization and 6-exo-dig oxo-cyclization sequence, resulting in continuous multiple C–C and C–O bond formation.