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Updated: Aug 13, 2026

Microwave-Assisted Preparation of 1-Aryl-1H-pyrazole-5-amines
Published on: June 23, 2019
Efficient library synthesis of imidazoles using a multicomponent reaction and microwave irradiation
E Gelens1, F J J De Kanter, R F Schmitz
1Department of Chemistry, Faculty of Exact Sciences, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Abstract:
Optimization of Radziszewski's four-component reaction employing a microwave-assisted protocol, led to a small library of 48 imidazoles with a success rate of 65% (conversion > 45%). All three diversity points of the four-component reaction were varied. Aromatic and aliphatic inputs were successfully implemented and mono-, di-, tri- and tetrasubstituted imidazoles with various substitution patterns were synthesized. Furthermore, unsymmetrical diketones could successfully be used which improved the intrinsic diversity of the method significantly. If the unsymmetrical diketone 1,2-phenylpropanedione (R1 and R2) was used two regioisomers were formed. Depending on the type of amine (R4) and aldehyde (R3) applied, regioselectivity was modest to good. Based on these results, a reaction mechanism is proposed.
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