DBU-Promoted Formal [4+2] Annulation Reactions of o-Chloromethyl Anilines with Azlactones

An efficient 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-mediated formal [4+2] annulation reaction of aza-ortho-quinone methides (aza-oQMs) (generated from o-chloromethyl anilines) with enolates (formed from azlactones) is disclosed, delivering biologically significant 3,4-dihydroquinolin-2(1H)-one derivatives in moderate to good yields. The salient features of this reaction include readily accessible starting materials, broad substrate scope, mild reaction conditions, removable protecting groups, and a scalable synthetic approach.