Synthesis of Pyran-4-one From Organic Precursor 4-Oxo-4H-pyran-2,6-dicarboxylic Acid

Abstract

Pyran-4-one (𝛾-pyrone (C5H4O2)), a conjugated enone, is a molecule of interest in the laser spectroscopy studies conducted in our lab. Spectroscopic parameters of the molecule’s electronic structure serve to test excited-state computational methods. However, 𝛾-pyrone comes at a high cost from commercial sources and can be synthesized from precursor molecule 4-oxo-4H-pyran-2,6-dicarboxylic acid (chelidonic acid, (C7H4O6)). Our goal is to synthesize quality samples of pyrone that are fit for use in our spectroscopic studies. We have followed a patented procedure for the synthesis of chelidonic acid, which involves a condensation followed by neutralization and an extensive reflux process. The resulting product is then decarboxylated via a reflux to make pyrone. This mixture is then worked up to isolate a pyrone/water solution. Pyrone has a high affinity for water and is stored in a desiccator until crystals form. We have successfully characterized both chelidonic acid and pyrone via H-NMR and IR spectroscopy, and after successful crystallization the resulting pyrone is deemed pure enough to use in our laser spectroscopic studies.