A Simple Synthesis of 5‐(2‐Aminophenyl)‐1 H ‐pyrazoles
2011; Wiley; Volume: 94; Issue: 9 Linguagem: Inglês
10.1002/hlca.201100055
ISSN1522-2675
AutoresM. Janjic, Rok Prebil, Uroš Grošelj, David Kralj, C. Malavasic, Amalija Golobič, Katarina Stare, Georg Dahmann, Branko Stanovnik, Jurij Svete,
Tópico(s)Synthesis of heterocyclic compounds
ResumoAbstract A four‐step synthesis of 1‐substituted 5‐(2‐aminophenyl)‐1 H ‐pyrazoles 5 as a novel type of histamine analogs and versatile building blocks for further transformations was developed. The synthesis starts from commercially available 2‐nitroacetophenone ( 12 ), which is converted into the enamino ketone 13 as the key intermediate. Cyclization of the key intermediate 13 with monosubstituted hydrazines 14a – 14l afforded the 5‐(2‐nitrophenyl)‐1 H ‐pyrazoles 17a – 17l . Finally, catalytic hydrogenation of the nitro compounds 17a, 17c – 17e , and 17g – 17j furnished the title compounds 5a, 5c – 5e , and 5g – 5j , respectively, in good yields. As demonstrated by some further transformations, additional functionalization of compounds 17 and 5 is feasible, either by electrophilic substitution at C(4) of the pyrazole ring, or at the NH 2 group.
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