Green and Efficient Protocol for the Synthesis of N-(2-Hydroxyethyl)anilines by the Alkylation Reaction in Ionic Liquid

Abstract

A green and efficient protocol for the synthesis of N-(2-hydroxyethyl)anilines by the selective alkylation reaction in ionic liquid [BMIM]BF₄ (1-butyl-3-methylimidazolium tetrafluoroborate) has been developed, eliminating the need for toxic and expensive catalysts and volatile organic solvents. The effects of the amount of ionic liquid, temperature, time, and substrate structure on the reaction were investigated. The conversion and selectivity of N-(2-hydroxyethyl)anilines obtained in ionic liquid [BMIM]BF₄ are significantly increased in comparison to those traditional methods. Furthermore, the ionic liquid could be easily separated and reused at least five times. It provided a simple and efficient alternative way for the industrial synthesis of N-(2-hydroxyethyl)anilines.

GRAPHICAL ABSTRACT

Keywords:

• Alkylation reaction
• ionic liquid
• N-(2-hydroxyethyl)anilines
• selectivity

Notes

^a Reaction conditions: 1 mmol aniline, 1 mmol 2-chloroethanol, 100 °C, 6 h.

^b Conversion and selectivity determined by HPLC.

^a Reaction conditions: 1 mmol aniline, 1 mmol [BMIM]BF₄, 100 °C, 6 h.

^b Conversion and selectivity determined by HPLC.

^a Reaction conditions: 1 mmol aniline, 1.5 mmol 2-chloroethanol, 1 mmol [BMIM]BF₄, 100 °C, 6 h.

^b Conversion and selectivity determined by HPLC.

^a Reaction conditions: 1 mol aniline, 1.5 mol 2-chloroethanol, 1 mol [BMIM]BF₄, 100 °C.

^b Conversion and selectivity determined by HPLC.

^a Reaction conditions: substrate 1/substrate 2 = 1 mmol/1.5 mmol, 1 mmol [BMIM]BF₄, 100 °C, 6 h.

^b Conversion and selectivity determined by HPLC.

^c Reaction conditions: substrate 1/substrate 2 = 1 mol/1.5 mol, 10 mmol [BMIM]BF₄, 100 °C, 6 h.

^a Reaction conditions: 1 mol aniline, 1.5 mol 2-chloroethanol, 1 mol ionic liquid, 100 °C, 6 h.

^b Conversion and selectivity determined by HPLC.