Synthesis of Aminopyrazoles from Isoxazoles: Comparison of Preparative Methods by in situ NMR Analysis

Abstract

A single-step method and a two-step method for the synthesis of aminopyrazoles from isoxazoles are presented and compared. Based on in situ NMR monitoring, both processes proceed through a ketonitrile. In the single-step process, hydrazine serves to both open the isoxazole to the unisolated ketonitrile intermediate and form the aminopyrazole. The two-step process involves ring opening of the isoxazole by deprotonation with hydroxide to generate the ketonitrile followed by the addition of acetic acid and hydrazine to form the aminopyrazole.

Key words

aminopyrazoles - isoxazoles - in situ NMR analysis - ketonitriles - heterocycles - regioselectivity

• References

• 1 Current address: Butler University, Department of Chemistry, 4600 Sunset Avenue, Indianapolis, IN 46208, USA.
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