A simple synthesis of 4-(2-aminoethyl)-5-hydroxy-1H-pyrazoles
2007; Elsevier BV; Volume: 63; Issue: 45 Linguagem: Inglês
10.1016/j.tet.2007.07.052
ISSN1464-5416
AutoresDavid Kralj, Uroš Grošelj, Anton Meden, Georg Dahmann, Branko Stanovnik, Jurij Svete,
Tópico(s)Synthesis and Reactions of Organic Compounds
ResumoAbstract A simple four-step synthesis of 4-(2-aminoethyl)-5-hydroxy-1H-pyrazoles 8 (or their 1H-pyrazol-3(2H)-one tautomers 8′) as the pyrazole analogues of histamine was developed. First, enamino lactam 3 was prepared as the key intermediate in two steps from 2-pyrrolidinone (1). Next, acid-catalysed ‘ring switching’ transformations of 3 with monosubstituted hydrazines 4 gave N-[(1-substituted 5-hydroxy-1H-pyrazol-4-yl)ethyl]benzamides 7a–k and N-[2-(2-heteroaryl-3-oxo-2,3-dihydro-1H-pyrazol-4-yl)ethyl]benzamides 7′l–o. Benzamides 7a–k and 7′l–o were finally hydrolysed by heating in 6 M hydrochloric acid to furnish 1-substituted 4-(2-aminoethyl)-5-hydroxy-1H-pyrazoles 8a–k and 4-(2-aminoethyl)-2-heteroaryl-1H-pyrazol-3(2H)-ones 8′l–o in good overall yields.
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