G. Eller, W. Holzer
Nov 1, 2004
Citations
0
Influential Citations
18
Citations
Journal
Heterocycles
Abstract
Starting from diethyl ethoxyrnethylenemalonate and 4-methoxy-benzylhydrazine (PMB-NHNH 2 ) 2-(4-methoxybenzyl)-2,4-dihydro-3H-pyrazol-3-one was prepared. Reaction of the latter with carboxylic acid chlorides / calcium hydroxide in 1,4-dioxane afforded 4-acyl-5-hydroxy-1-PMB-1H-pyrazoles, whereas with dimethylformamide diethyl acetal or benzaldehyde the corresponding (E)-4-dimethylaminomethylene or (E)-4-benzylidene products, respectively, were obtained. The PMB protecting group could be conveniently removed from the pyrazole nucleus by treatment with trifluoroacetic acid to give the N-unsubstituted pyrazolones. Detailed NMR spectroscopic investigations ( 1 H, 1 3 C, 1 5 N) with the obtained compounds are presented.