Synthesis and Characterization of 9-Hydroxyphenalenone Using 2D NMR Techniques

Abstract

9-Hydroxyphenalenone is a planar multicyclic β-keto–enol, which is synthesized via a Friedel–Crafts acylation followed by acid-catalyzed intramolecular Michael addition with the loss of a phenyl group in a one-pot reaction during a four-hour lab period. Tautomerization of the andbeta-keto–enol results in C2ν symmetry on the NMR time scale, which simplifies the spectra and provides a unique structure for teaching 2D NMR spectroscopy. The 1H and 13C assignments can be made using 1D and 2D NMR techniques and data collection can be reduced to less than twenty minutes with optimized parameters.