Efficient acetylation of primary amines and amino acids in environmentally benign brine solution using acetyl chloride

Abstract

Acetyl chloride is one of the most commonly available and cheap acylating agent but its high reactivity and concomitant instability in water precludes its use to carry out acetylation in aqueous medium. The present methodology illustrates the efficient acetylation of primary amines and amino acids in brine solution by means of acetyl chloride under weakly basic condition in the presence of sodium acetate and/or triethyl amine followed by trituration with aqueous saturated bicarbonate solution. This effort represents the first efficient use of this most reactive but cheap acetylating agent to acetylate amines in excellent yields in aqueous medium. This is a potentially useful green chemical transformation where reaction takes place in environment-friendly brine solution leading to easy work-up and isolation of the amide derivatives. Mechanistic rationale of this methodology is also important. Aromatic and aliphatic primary amines and amino acids have been acetylated efficiently in brine solution with acetyl chloride under weakly basic conditions in the presence of sodium acetate and/or triethyl amine. The methodology demonstrates successful use of acetyl chloride as a substitute of acetic anhydride for the purpose of acetylation in aqueous medium.