Mechanistic investigation inspired “on water” reaction for hydrobromic acid-catalyzed Friedel–Crafts–type reaction of β-naphthol and formaldehyde

5 years ago

Mechanistic investigation inspired “on water” reaction for hydrobromic acid-catalyzed Friedel–Crafts–type reaction of β-naphthol and formaldehyde

Xiaoying Zhang, Mang Wang, Yang Yang, Jingping Zhang, Haiyan Yuan, Shanshan Cao

The mechanism of the HBr-catalyzed Friedel-Crafts-type reaction between β-naphthol and HCHO was investigated by DFT to improve this reaction. The HBr-H2O co-catalyzed the preferential pathway undergoes the concerted nucleophilic addition and hydrogen shift, stepwise followed by H2O elimination and the CC bond formation. The origin of the high catalytic activity of HBr is ascribed to CH···Br− and OH···Br− interactions, which suggest that the active species is Br−. Moreover, water molecules efficiently assist in improving the activity of Br−. The computational results show that solvent polarity profoundly affects the activation barriers. To our delight, the activation barrier of the rate-determining step for the favored pathway in water is comparable (0.6 kcal/mol difference) with that in acetonitrile. The experimental observation further confirmed our results and demonstrated that the title reaction can be successfully achieved “on water.” Therefore, we open a new efficient and green strategy for the synthesis of biphenol derivatives. © 2017 Wiley Periodicals, Inc. DFT investigations are carried out to improve the HBr-catalyzed Friedel–Crafts reaction between β-naphthol and HCHO. Economic reaction approach was realized via water solvent. The “on water” reaction with the yield of 95% shows that the formation of biphenol derivatives no longer relies on toxic solvents.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/jcc.24877