Chemoselective Synthesis of Pyridine Derivatives

Aldehyde 6 (1 equiv.) was dissolved in wet MeOH at 25 °C. The required aniline/amine (1 equiv.) was added dropwise by a syringe to the reaction flask followed by addition of ammonium bicarbonate (1 equiv.). Glyoxal (1 equiv.) was then added dropwise by a syringe and the reaction was allowed to stir at 25 ° C for 8 h. Upon complete conversion of the aldehyde, as observed by thin-layer chromatography, tetrabutylammonium fluoride was added dropwise by syringe and the reaction was allowed to stir at 25 °C for 30 min, at which time, the reaction was quenched with sat. aq. NH₄Cl and extracted with EtOAc. The organic layers were combined, dried over Na₂SO₄, and concentrated in vacuo. All compounds were purified via flash chromatography utilizing 95:5 (CH₂Cl₂:MeOH) as the eluent. Yields and characterization for all compounds are provided in the supplementary information.