Pyrazine- and pyridine-substituted prop-2-yn-1-ols, but-3-yn-2-ols, and but-3-yn-2-ones - purification, stability, and handling revised

A short series of alkynyl-substituted pyrazine and pyridine derivatives was synthesized by the palladium-catalyzed Sonogashira cross-coupling reactions between aryl halides and alkynes. All the products are either white solids or colorless liquids, which is partly in contrast to previous reports. After purification, a color change or intense darkening was observed, in some cases starting almost immediately. Both, the nature of the heteroaromatic ring and the substituents of the alkyne moiety affect their stability. Herein details of synthesis, characterization, and, most importantly, purification and handling are reported.