Access to 8-Azachromones via Activation of C–H in N-Oxides

2-(Substituted amino)-8-azachromones from 4,6-Diaryl-2-pyridones: A Synthetic Strategy toward Compounds of Broad Structural Diversity

3-Acetoacetyl-4,6-diaryl-2-pyridones are synthesized in three steps from chalcones and then condense with carbon disulfide to afford 8-azachromones containing a methylthio group at C2. This leaving group offers an entry point for the insertion of more complex moieties via nucleophilic substitution. For this purpose, N-nucleophiles are explored according to their positions in the Mayr's nucleophilicity scale (N parameter), and three main classes are distinguished depending on whether the substitution takes place from their neutral forms, from their deprotonated anionic forms, or under nucleophilic catalysis. A broad range of primary and secondary amines may be inserted by this method, including enantiomerically pure amino acids, enabling us to explore structural diversity.

One-Pot Selective Saturation and Functionalization of Heteroaromatics Leading to Dihydropyridines and Dihydroquinolines

A one-pot regioselective two C-C-bond-forming dearomatization of pyridines and quinolines is disclosed. Two 3,4-betaines are identified for the first time as very useful organic synthons in heterocyclic chemistry. Furthermore, the chemical reactivity of the prepared trifluoromethyl ketones, a new type of push-pull enones, has been explored to develop straightforward methods for their functionalization. This protocol represents a breakthrough in the dearomatization of heteroaromatics as both the selective saturation and functionalization of heteroaromatics are achieved in high efficiency by the attachment of two substituents, including the valuable trifluoromethyl ketone group.

Synthesis of 3-(2-quinolyl) chromones from ynones and quinoline N-oxides via tandem reactions under transition metal- and additive-free conditions

The synthesis of 3-(2-quinolyl) chromones from ynones and quinoline N-oxides via a sequential [3+2] cycloaddition/ring-opening/O-arylation reaction under transition metal- and additive-free conditions is reported.

A concise synthesis of 3-substituted-7-amino-6-carboxyl-8-azachromones

We report on an approach to truncate the tricyclic 5H-chromeno[2,3-b]pyridin-5-one core of amlexanox, an approved drug under investigation for the treatment of obesity, to the bicyclic 4H-pyrano[2,3-b]pyridin-4-one (8-azachromone) core. A short, concise synthesis generates a key intermediate with requisite functionality on the pyridyl A-ring and iodo functionality on the 4-pyrone B-ring upon which palladium-catalyzed cross-coupling and subsequent reactions generate representative analogues. One of these shows a 14.2-fold increase in aqueous solubility over amlexanox.