Exploration of C5—C6-Unsubstituted 1,4-Dihydropyridines for the Construction of exo-Hexahydro-1H-chromeno[3,4-h][1,6]naphthyridine-3-carboxylates Using a Stereoselective Povarov Reaction.

A wide variety of substituted exo -hexahydro-1 H -chromeno[3,4- h ][1,6]naphthyridine-3-carboxylate derivatives have been synthesized from 3-aminocoumarins, aldehydes, and 5,6-unsubstituted 1,4-dihydropyridine derivatives in the presence of 10 mol% of ytterbium(III) triflate in acetonitrile at room temperature using a one-pot Povarov reaction. Some of the salient features of this protocol are: good yields and no need for an aqueous workup procedure or chromatographic separation.