Metal-Free [2+3] Dipolar Cycloaddition/Denitration Cascade between Nitroalkenes and ?-Diazoesters: Regioselective Access to Functionalized NH?Pyrazoles
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Date
2024
Authors
Journal Title
Asian Journal of Organic Chemistry
Journal ISSN
Volume Title
Publisher
John Wiley and Sons Inc
Abstract
An efficient one-pot synthesis of 1H-pyrazoles has been realized via cascade cyclocondensation of ?-nitroalkenes as C2 synthon with ?-diazoesters as C1N2 unit. The reaction proceeds via concomitant formation of two new (C?N & C?C) bonds in one stretch leading to ethyl-5-nitro-4-phenyl-4,5-dihydro-3H-pyrazole-3-carboxylate intermediate, which undergoes base mediated denitration enabling the formation of NH?pyrazoles. This protocol not only features easy operation, catalyst?free conditions, good to high yields, wide scope and late-stage functionalization, but also opens up a new avenue for synthetically demanding and structurally non-traditional pyrazoles. A combination of experimental and DFT studies provide evidence for the proposed mechanism. � 2024 Wiley-VCH GmbH.
Description
Keywords
1,3-Dipolar cycloaddition, DFT Studies, Nitroalkenes, Pyrazoles, Regioselective, ?-Diazoesters