A Simple Synthesis of 5-(2-Aminophenyl)-1H-pyrazoles

作者：Janjic Monika; Prebil Rok; Groselj Uros; Kralj David; Malavasic Crt; Golobic Amalija; Stare Katarina; Dahmann Georg; Stanovnik Branko; Svete Jurij^*

来源：Helvetica Chimica Acta, 2011, 94(9): 1703-1717.

DOI：10.1002/hlca.201100055

A four-step synthesis of 1-substituted 5-(2-aminophenyl)-1H-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)-1H-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 NH2 group.

• 出版日期2011-9