Synthesis 2021; 53(04): 723-730
DOI: 10.1055/s-0040-1705957
paper

Synthesis of Azocane- and Oxocane-Annulated Furans by a [2+2] Photocycloaddition–Ring-Opening Cascade

Authors

  • Xinyao Li

  • Christian Jandl

  • Thorsten Bach

    Department Chemie and Catalysis Research Center (CRC), Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany   Email: thorsten.bach@ch.tum.de

Financial support by the Deutsche Forschungsgemeinschaft (GRK 1626) is gratefully acknowledged. X.L. thanks the Alexander von Humboldt Foundation for a research fellowship.


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Dedicated to Professor Paul Knochel on the occasion of his 65th birthday

Abstract

The title compounds were synthesized from readily available quinolone and coumarin derivatives by a cascade reaction (12 examples, 90–98% yield). The cascade comprised a [2+2] photocycloaddition which occurred upon sensitized irradiation at λ = 420 nm (or direct UV irradiation at λ = 366 nm) and a subsequent acid-catalyzed ring-opening reaction. A variety of substituents are compatible with the conditions and a 3-alkyl group in the coumarin (or quinolone) is crucial to achieve a high chemoselectivity. Key to the success of the ring opening is the formation of a 4,5,5a-trihydrocyclobuta-2H-furan containing a strained bridgehead double bond which stems from the allenyl group tethered to the 4-position of the starting materials.

Supporting Information



Publication History

Received: 18 September 2020

Accepted: 29 September 2020

Article published online:
05 November 2020

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