Diastereoselective Synthesis of CF₃‐Pyrano[3,4‐c]quinolones from Hetero‐Dendralenes and Aldehydes

Herein, we demonstrate an Oxa‐Diels‐Alder reaction of 3‐trifluoroacetyl‐4‐methyl‐quinolin‐2(1 H )‐one with aldehydes in the presence of a base to engineer the functionalized pyrano[3,4‐ c ]quinolones. This reaction proceeds through an in‐situ generated hetero dendralene intermediate and features perfect stereoselectivity on a wide range of substrates with excellent atom economy. The high electron‐withdrawing nature of CF 3 ‐group is responsible for making the methyl group present in quinolone moiety more acidic to furnish the corresponding hetero dendralene intermediate.