Chemoselective Intermolecular Cross-Enolate-Type Coupling of Amides

A new approach for
the synthesis of 1,4-dicarbonyl compounds is
reported. Chemoselective activation of amide carbonyl functionality
and subsequent umpolung via N-oxide
addition generates an electrophilic enolonium species that can be
coupled with a wide range of nucleophilic enolates. The method conveys
broad functional group tolerance on both components, does not suffer
from formation of homocoupling byproducts and avoids the use of transition
metal catalysts.