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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Veröffentlicht in:	Angewandte Chemie International Edition Jg. 57; H. 1; S. 140 - 145
Hauptverfasser:	te Grotenhuis, Colet, van den Heuvel, Naudin, van der Vlugt, Jarl Ivar, de Bruin, Bas
Format:	Journal Article
Sprache:	Englisch
Veröffentlicht:	WEINHEIM Wiley 02.01.2018 Wiley Subscription Services, Inc John Wiley and Sons Inc
Ausgabe:	International ed. in English
Schlagworte:	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-Zugang:	Volltext
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Zusammenfassung:	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.
Bibliographie:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 content type line 23
ISSN:	1433-7851 1521-3773 1521-3773
DOI:	10.1002/anie.201711028