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. 2015 Feb 16;54(8):2501-4.
doi: 10.1002/anie.201410462. Epub 2015 Jan 16.

Orchestrated triple C-H activation reactions using two directing groups: rapid assembly of complex pyrazoles

Weibo Yang  1 , Shengqing Ye, Dewey Fanning, Timothy Coon, Yvonne Schmidt, Paul Krenitsky, Dean Stamos, Jin-Quan Yu
Affiliations

Orchestrated triple C-H activation reactions using two directing groups: rapid assembly of complex pyrazoles

Weibo Yang et al. Angew Chem Int Ed Engl. .

Abstract

A sequential triple C-H activation reaction directed by a pyrazole and an amide group leads to the well-controlled construction of sterically congested dihydrobenzo[e]indazole derivatives. This cascade reaction demonstrates that the often problematic competing C-H activation pathways in the presence of multiple directing groups can be harvested by design to improve step economy in synthesis. Pyrazole as a relatively weak coordinating group is shown to direct Csp3-H activation for the first time.

Keywords: CH activation; benzo[e]indazoles; cascade reactions; pyrazole.

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Figures

Scheme 1
Scheme 1
Biologically active pyrazoles and benzo[e]indazole derivatives.
Scheme 2
Scheme 2
Pyrazole-directing C–H acitvations.
Scheme 3
Scheme 3
Triple C–H activation reactions using two directing groups.
Scheme 4
Scheme 4
Mechanistic investigations.
Scheme 5
Scheme 5
Proposed catalytic pathway.
See this image and copyright information in PMC

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