Choline chloride: ۲ ZnCl۲ catalyzed efficient one-pot regioselective synthesis of dihydrobenzofuro[۲,۳-b]benzofuran

The reaction of ۲-naphthol and also para-substituted phenols with glyoxal in presence of choline chloride: ۲ ZnCl۲ [ChCl: ۲ZnCl۲], a deep eutectic solvent (DES), as a green catalyst was studied. The amount of catalyst, solvent type, temperature, and time on the yield of reaction were investigated. It was found that the optimal condition included ۱۰% mol ratio of catalyst (mol percentage of DES to glyoxal), solvent-free condition (۶۰ °C) and the time about one hour. Under these conditions, products are obtained in good yield (۸۰%). The products were characterized on the basis of FT-IR, ۱H-NMR, ۱۳C-NMR spectra and comparison of melting point with authentic sample. The NMR spectra indicated that of the two probable isomers with an acetal and ether structure; the aforementioned reaction, regioselectively, furnished compounds with acetal linkage, rather than ether.

Keywords:

Regioselective synthesis , benzofuro[۲ , ۳-b]benzofuran , Deep Eutectic Solvent , choline chloride: ۲ ZnCl۲