Synthesis of 3-(2-aminoethyl)-5-hydroxy-1H-pyrazole derivatives

Abstract

Treatment of β-keto ester 8 with hydrazines 9a-g gave 1'-substituted tert-butyl 2-(5-hydroxy-1Hpyrazol- 3-yl)ethylcarbamates 10a-e and 2-(5-oxo-2,5-dihydro-1H-pyrazol-3-yl)ethylcarbamates 11f,g. Acidolytic deprotection of 10b,c afforded the corresponding 3-(2-aminoethyl)-5-hydroxy- 1H-pyrazoles 6b,c in good yields. Acylation of 6 gave either the N-acyl compounds 12b,c and 13c, or the N,O-diacyl derivative 14. Next, three N,N-dialkyl analogues 15a,b and 26c were prepared from dimethyl acetone-1,3-dicarboxylate 21 via condensation with hydrazines 9a and 9h followed by hydrolysis of the esters 22a,b, amidation of the carboxylic acids 23a,b, and reduction of the tertiary carboxamides 24a and 25b,c. © ARKAT-USA, Inc.