Issue 45, 2017

The diaza-Nazarov cyclization involving a 2,3-diaza-pentadienyl cation for the synthesis of polysubstituted pyrazoles

Abstract

An unprecedented iodine-mediated diaza-Nazarov (DAN) type cyclization for the construction of substituted pyrazoles from easily available starting materials via an enamine–iminium ion intermediate is described. The oxidative cyclization worked under green conditions with remarkable regioselectivity. This one-pot, efficient and operationally simple three-component intramolecular regioselective DAN cyclization displayed a wide range of substrate scope. The dichotomy of reaction pathways has been explored with density functional theory in the gas phase and solution phase. Of the possible 1,5-, 1,6-, and 1,7-electrocyclizations, the DAN cyclization, i.e., the 1,5-pathway offers the lowest activation energy barrier supporting our experimental observations.

Graphical abstract: The diaza-Nazarov cyclization involving a 2,3-diaza-pentadienyl cation for the synthesis of polysubstituted pyrazoles

Supplementary files

Article information

Article type
Paper
Submitted
05 Aug 2017
Accepted
31 Oct 2017
First published
08 Nov 2017

Org. Biomol. Chem., 2017,15, 9643-9652

The diaza-Nazarov cyclization involving a 2,3-diaza-pentadienyl cation for the synthesis of polysubstituted pyrazoles

B. Aegurla and R. K. Peddinti, Org. Biomol. Chem., 2017, 15, 9643 DOI: 10.1039/C7OB01949A

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