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Updated: Jun 9, 2026
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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Carbene-Catalyzed [4 + 3] Annulation Strategy for the Construction of Benzo-Fused Nitrogen-Rich Seven-Membered
Molugumati Rambabu1,2, Kandivalasa Kamala1,2, Surisetti Suresh1,2
1Department of Organic Synthesis & Process Chemistry, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500007, India.
Abstract:
In this Letter, we describe an N-heterocyclic carbene (NHC)-catalyzed [4 + 3] annulation approach that enables the streamlined assembly of azepine architectures through an acyl azolium-driven process. The transformation employs ortho-functionalized benzaldehydes and hydrazonyl chlorides as readily available coupling partners. This process proceeds through the formation of an NHC-derived acyl azolium intermediate from ortho-functionalized benzaldehyde, which then undergoes in situ generation of an ortho-quinone methide (o-QM) or aza-o-QM acting as a 1,4-dipolar species. Concurrently, base-mediated activation of hydrazonyl chloride produces a 1,3-dipole in situ. The synergistic interplay of these reactive intermediates culminates in a facile formal [4 + 3] annulation, delivering structurally diverse benzo-fused triazepine and oxadiazepine derivatives in moderate to high yields.
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