Catalytic Dibenzocyclooctene Synthesis via Cobalt(III)–Carbene Radical and ortho‐Quinodimethane Intermediates

The metalloradical activation of ortho‐benzallylaryl N‐tosyl hydrazones with [Co(TPP)] (TPP=tetraphenylporphyrin) as the catalyst enabled the controlled exploitation of the single‐electron reactivity of the redox non‐innocent carbene intermediate. This method offers a novel route to prepare eight‐me...

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Bibliographic Details
Published in:Angewandte Chemie International Edition Vol. 57; no. 1; pp. 140 - 145
Main Authors: te Grotenhuis, Colet, van den Heuvel, Naudin, van der Vlugt, Jarl Ivar, de Bruin, Bas
Format: Journal Article
Language:English
Published: WEINHEIM Wiley 02.01.2018
Wiley Subscription Services, Inc
John Wiley and Sons Inc
Edition:International ed. in English
Subjects:
Base metal
carbene radicals
Catalysis
Chemical synthesis
Chemistry
Chemistry, Multidisciplinary
Cobalt
Communication
Communications
dibenzocyclooctenes
Hydrazones
Intermediates
metalloradicals
ortho-quinodimethanes
Physical Sciences
Reaction mechanisms
Science & Technology
carbene radicals
REAGENTS
VERSATILE
ortho-quinodimethanes
8-MEMBERED RINGS
CONSTRUCTION
dibenzocyclooctenes
metalloradicals
CYCLOPROPANATION
cobalt
CYCLIZATION
N-TOSYLHYDRAZONES
ISSN:1433-7851, 1521-3773, 1521-3773
Online Access:Get full text
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Summary:The metalloradical activation of ortho‐benzallylaryl N‐tosyl hydrazones with [Co(TPP)] (TPP=tetraphenylporphyrin) as the catalyst enabled the controlled exploitation of the single‐electron reactivity of the redox non‐innocent carbene intermediate. This method offers a novel route to prepare eight‐membered rings, using base metal catalysis to construct a series of unique dibenzocyclooctenes through selective Ccarbene−Caryl cyclization. The desired eight‐membered‐ring products were obtained in good to excellent yields. A large variety of aromatic substituents are tolerated. The proposed reaction mechanism involves intramolecular hydrogen atom transfer (HAT) to CoIII–carbene radical intermediates followed by dissociation of an ortho‐quinodimethane that undergoes 8π cyclization. The mechanism is supported by DFT calculations, and the presence of radical‐type intermediates was confirmed by trapping experiments. Metalloradical activation of the shown N‐tosyl hydrazones with [Co(TPP)] provides an effective method for the construction of a series of unique dibenzocyclooctenes in good to excellent yields. The proposed reaction mechanism involves intramolecular hydrogen atom transfer to the key CoIII–carbene radical followed by dissociation of an ortho‐quinodimethane, which then undergoes 8π cyclization.
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ISSN:1433-7851
1521-3773
1521-3773
DOI:10.1002/anie.201711028