ZnBr₂-Catalyzed and Microwave-Assisted Synthesis of 2,3-Unsaturated Glucosides of Hindered Phenols and Alcohols

Abstract

Zinc bromide (ZnBr₂) under microwave irradiation efficiently catalyzed the Ferrier reaction of hindered phenols and alcohols to afford the corresponding α-2,3-unsaturated glucoside acetates in good yields and with good stereoselectivity. The reaction affords a facile access to new 2,3-dideoxyglucosides of important phenolic and alcoholic constituents of spices.

GRAPHICAL ABSTRACT

Keywords:

• Alcohols
• Ferrier reaction
• microwave
• phenols
• 2,3-unsaturated 1-O-glucosides
• ZnBr₂

ACKNOWLEDGMENTS

The authors thank Ram Rajasekharan, Director, CFTRI, for his support and constant encouragement for the work, and appreciate the help from J. R. Manjunatha, Technical Officer, Plantation Products, Spices and Flavour Technology Department, CFTRI, for NMR studies of compounds. Padmere Mukund Lakshman and M. Asha, Central Instruments Facility and Services Department, CFTRI, are acknowledged for their assistance in HRMS and IR analyses.

Notes

^a No product formation.

^a Isolated yields.

^b Ratio was determined by integration of the anomeric protons in ¹H NMR spectra of crude products.

^a Isolated yields.

^b Ratio was determined by integration of the anomeric protons in ¹H NMR spectra of crude products.

^a Isolated yields.

^b Ratio was determined by integration of the anomeric protons in ¹H NMR spectra of crude products.

^c Anomeric ratio could not be deciphered.

^a Isolated yields.

^b Ratio was determined by integration of the anomeric protons in ¹H NMR spectra of crude products.