Iron (III) Chloride Hexahydrate as a Highly Efficient Catalyst for Acetylation of Protic Nucleophiles with Acetic Anhydride under Solvent-free Conditions

Background: Acetylation of protic nucleophiles is used to protect these functional groups. Most of the methods described in the literature use solvents, one or more equivalent of toxic bases or expensive and toxic catalysts. Therefore, new methodologies, above all, greener and more economical procedures, are still in demand. Objective: An eco-efficient method was developed for the acetylation of alcohols, phenols, thiols, amines, and carbohydrates, using acetic anhydride and a catalytic amount of the environmentally benign and inexpensive FeCl3.6H2O, under solvent-free conditions. Methods: Acetylation of a variety of protic nucleophiles was performed using 0.2 mol % of FeCl3.6H2O as the catalyst, and 1.2 equivalent of Ac2O as the acetylating agent at room temperature and under solvent-free conditions. Results: This procedure appears to be highly efficient and promoted rapid and quantitative acetylation under simple and minimum manipulation. Chromatography or recrystallization was generally not necessary for the purification of products. Conclusion: This eco-friendly protocol appears to be potentially universally applicable in organic design to protect protic nucleophiles and isscalable for industrial fields.