FeCl₃ · 6H₂O-Catalyzed Acceleration of the Acylation of Sodium Azide with N-Acylbenzotriazoles

Abstract

Catalyzed by ferric chloride hexahydrate (FeCl₃ · 6H₂O), the acylation of sodium azide with N-acylbenzotriazoles was greatly accelerated in a mixed solvent of acetone and water. Thus, good to excellent yields of a variety of acyl azides were obtained at room temperature in a short time. Furthermore, because of the complete conversion of N-acylbenzotriazoles and the easy removal of the by-product, purification by column chromatography was no longer required, which made the protocol suitable for large-scale preparation.

Keywords:

• Acylation
• acyl azides
• N-acylbenzotriazoles
• ferric chloride hexahydrate (FeCl₃ · 6H₂O)
• sodium azide

ACKNOWLEDGMENT

We are grateful to the National Natural Science Foundation of China (No. 20802070) for financial support.

Notes

^a All the runs were carried out with 1 mmol of N-benzoyl benzotriazole in 3 mL of the solvent, fresh sodium azide solution (3 mmol of sodium azide in 1 mL of water) and 5 mol% of FeCl₃ · 6H₂O.

^b The conversion of N-benzoyl benzotriazole was determined by HPLC.

^c The time required in the absence of FeCl₃ · 6H₂O as reported in Ref. [4].

^a Yields were isolated yields and based on N-acylbenzotriazoles.

^b The yields using the methods reported in Ref. [4] were listed in the parentheses.

^c With 5 mol% of catalyst, incomplete conversion of 1d was observed, which would lead to the isolation of product 2c by column chromatography.

^d Product 2q was determined by ¹H NMR, but it was contaminated by 1q.