Polyphosphoric Acid–Mediated, One-Pot, Novel Reactions to Build Polymethoxyarylnaphthalene Lignans

Abstract

The one-pot reaction of succinic anhydride with 1,2-dimethoxybenzene furnished two structurally complicated polymethoxyarylnaphthalene lignans, polymethoxyarylnaphthol 1 as the minor product and polymethoxynaphtho[1,2-b]oxacycloheptatrienone 2 as the major product, in the presence of a small amount of polyphosphoric acid (PPA) as catalyst at 140°C and yielded 2 as a single product in good yield when a large amount of PPA as solvent was employed at 60–80°C. The novel structures of 1 and 2 were elucidated from ¹H NMR, ¹³C NMR, infrared (IR), and Electrospray ionization–mass spectrometry (ESI-MS) and further confirmed by x-ray diffractions. The possible mechanisms for the formation of 1 and 2 were also proposed.

Keywords:

• Arylnaphthalene lignan
• Friedel–Crafts acylation
• one pot
• polyphosphoric acid
• synthesis
• x-ray diffraction

ACKNOWLEDGMENT

The authors are very grateful to Professor Jiong Jia of Shandong University for recording of part of the NMR spectra, collecting x-ray diffraction data of one of the two crystals (2), and discussing the work.