Issue 13, 2021

An unusual reaction mode of 1-phenylpyrazolidinones toward diazonaphthalen-2(1H)-ones featuring cascade C(sp2)–H and C(sp3)–H bond cleavage

Abstract

Herein, a novel synthesis of pyrazolidinone fused 1,3-benzooxazepine derivatives via a formal [4 + 3] annulation reaction of 1-phenylpyrazolidinones with diazonaphthalen-2(1H)-ones is presented. Mechanistically, the formation of products involves an unprecedented reaction mode of 1-phenylpyrazolidinone featuring cascade C-alkylation/C-annulation through C(sp2)–H/C(sp3)–H bond cleavage instead of C-alkylation/N-annulation via C(sp2)–H/N–H bond cleavage as reported in previous studies on the reaction of 1-phenylpyrazolidinone. In this cascade process, the pyrazolidinone unit firstly acts as an embedded directing group to assist in the alkylation and subsequently it is transformed into a cyclic iminium species to undergo an intramolecular nucleophilic addition with the in situ formed naphthol unit to give the polycyclic product. Compared with literature methods for the preparation of N-fused 1,3-oxazepines, the protocol developed herein has advantages such as easily accessible starting materials, structurally complex and biologically attractive products, a unique mechanistic pathway, and excellent chemo/regioselectivity.

Graphical abstract: An unusual reaction mode of 1-phenylpyrazolidinones toward diazonaphthalen-2(1H)-ones featuring cascade C(sp2)–H and C(sp3)–H bond cleavage

Supplementary files

Article information

Article type
Research Article
Submitted
21 fev 2021
Accepted
21 may 2021
First published
25 may 2021

Org. Chem. Front., 2021,8, 3238-3243

An unusual reaction mode of 1-phenylpyrazolidinones toward diazonaphthalen-2(1H)-ones featuring cascade C(sp2)–H and C(sp3)–H bond cleavage

M. Wang, L. Zhang, X. Chen, X. Zhang and X. Fan, Org. Chem. Front., 2021, 8, 3238 DOI: 10.1039/D1QO00305D

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