K. Kirschke, Petra Hübner, G. Lutze
Feb 14, 1994
Citations
0
Influential Citations
9
Citations
Journal
European Journal of Organic Chemistry
Abstract
Ring Transformations of 1-Oxa-5,6-diazaspiro[2.4]hept-6-en-4-ones into 4,5-Dihydro-4-hydroxy-1H-pyrazole-4-carboxylic Acid Derivatives Spiro epoxides 3 were synthesized from 1H-pyrazol-5(4H)-ones 1 by Knoevenagel condensation with acetone or benzaldehyde and subsequent epoxidation of 2 with hydrogen peroxide. 3 reacts with nucleophiles under ring transformation to 4,5-dihydro-4-hydroxy-1H-pyrazole-4-carboxylic acid derivatives 5. In three cases the intermediate 6 was isolated. 5b, c undergo by dehydrogenation with chloranil rearrangement to 4,5-dihydro-4-oxo-1H-pyrazole-5-carboxylic acid derivatives 7b, c.