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DOI: 10.1055/s-0028-1083186
An Improved Preparation of 3-Alkoxypyrazoles
Publication History
Received
15 April 2008
Publication Date:
16 October 2008 (online)


Abstract
The condensation between alkyl acetoacetates and hydrazines constitutes the very well-known Knorr synthetic method leading to pyrazol-3/5-ones. However, contemporary reports describe an alternate reaction pathway leading to low yields of 3/5-alkoxypyrazoles using hydrazine salts. No general method for the selective synthesis of 3-alkoxypyrazoles has been reported to date, hence we focused on this side reaction in an attempt to turn it into the main transformation. Depending on the starting material, various 3-alkoxypyrazoles (methoxy, ethoxy, benzyloxy, isopropoxy, allyloxy) were obtained in up to 56% yield.
Key words
condensation - cyclizations - heterocycles - pyrazoles - Knorr reaction