Solid–Liquid Phase Alkylation of N-Heterocycles: Microwave-Assisted Synthesis as an Environmentally Friendly Alternative

Abstract

The solid–liquid phase alkylation of a variety of five-membered N-heterocycles (carbazole, imidazole, benzimidazole, and indole-3-carbaldehyde) was carried out under different conditions. The use of alkali carbonate in dimethylformamide or in MeCN (in the latter case, in the presence of a phase-transfer catalyst) is a suitable method to prepare the corresponding N-alkylated products in an efficient way. In most cases, the solventless, microwave-assisted reaction is an environmentally friendly alternative to traditional methods.

Keywords:

• N-Alkylation
• N-heterocycles
• microwave synthesis
• phase-transfer catalysis
• solid–liquid phase

Notes

^a Determined on the basis of GC or LC.

Note. Because of the risk of explosion, the reaction of carbazole and ethyl halogenoacetates may be dangerous above 100 °C under MW conditions.

^a Determined on the basis of GC.

^a Determined on the basis of GC.

^a Determined on the basis of GC.

^a Determined on the basis of GC.