Palladium‐Catalyzed Cascade for Rapid Access to Tetrahydro‐4<i>H</i>‐pyrazolo[3,4‐<i>d</i>]pyrrolo[1,2‐<i>a</i>]pyrimidin‐4‐one Tetracyclic Fused Heterocycles

Abstract The cascade reaction is an attractive strategy for building fused heterocycles. We report the first synthetic methodology to construct (6 R )‐6‐hydroxy‐1,3a,6,11a‐tetrahydro‐4 H ‐pyrazolo[3′,4′:4,5]pyrimido[2,1‐ a ]isoindol‐4‐one fused heterocycles based on a cascade sequence of Suzuki coupling to form a C−C bond and base‐mediated intramolecular cyclization to form a C−N bond. This protocol exhibits high stereospecificity, as intramolecular cyclization generates a chiral center with exclusive R ‐configuration in the product. A mechanism for the cascade reaction is proposed based on density functional theory calculations.