New Journal of Chemistry p. 16131 - 16137 (2019)
Update date:2022-09-26
Topics: Enaminones Regioselective synthesis Enamines MSA-catalyzed 1,3,4-triAnd 1,3,4,5-tetrasubstituted pyrazoles
Duan, Liancheng
Zhou, Hui
Gu, Yucheng
Gong, Ping
Qin, Mingze
In the present work, an efficient regioselective synthesis of 1,3,4-tri- and 1,3,4,5-tetrasubstituted pyrazoles via a methanesulfonic acid (MSA)-catalyzed reaction of hydrazones with enaminones or enamines is reported. Mechanistically, the formation of the title compounds involves the [2+3] cycloaddition of hydrazones with enaminones or enamines followed by aromatization with acid and oxygen. This convenient method under mild conditions with various hydrazones, enaminones, and enamines was well-tolerated to afford products in good to excellent yields. Compared with the literature methods, this strategy has advantages such as materials that are available economically, metal-free catalysis, excellent regioselectivity, and high efficiency.
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