Additive‐Controlled Divergent [4+2] Cycloaddition and 1,4‐Michael Addition Reaction of Benzofuran‐Derived Azadienes with Enamides: Access to Decahydrobenzofuro[3,2‐b]quinolines.

We describe herein the additive‐controlled divergent [4+2] cycloaddition and 1,4‐Michael addition reaction of benzofuran‐derived azadienes (BDAs) with enamides. An unprecedented [4+2] cycloaddition reaction of BDAs and enamide compounds was developed in the presence of 4 Å MS, providing a variety of structurally complex decahydrobenzofuro[3,2‐b]quinolines (13 examples) in moderate to excellent yields (59–98 % yields) with single diastereoisomer obtained. While employing MgSO4 as desiccant, the chemoselectivity was switched to the 1,4‐addition reactions, leading to a wide range of highly functionalized hybrids of benzofurans and enamide compounds (25 examples) in 25–94 % yields under mild conditions. [ABSTRACT FROM AUTHOR]