Double-Oxidative Dehydrogenative (DOD) [4 + 2]-Cyclization/Oxidative Aromatization Tandem Reaction of Glycine Derivatives with Ethylbenzenes.

The double-oxidative dehydrogenative (DOD) cyclization represents one of the most straightforward and atom-economical methods for cyclic structure formation. A Cu(II)/DDQ/O2 system-catalyzed DOD [4 + 2]-annulation/oxidative aromatization tandem reaction of readily available glycine derivatives and alkylbenzenes was established. This approach facilitates rapid access to a broad scope of substituted quinoline-2-carboxylate derivatives, an important motif in drug discovery. The reaction could feasibly be applied to a 10 gram-scale synthesis.