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Synlett 2023; 34(09): 1063-1067
DOI: 10.1055/a-2004-3771
DOI: 10.1055/a-2004-3771
letter
Photocatalytic Spirocyclization of 2-Alk-ω-enyl-Substituted Cycloalkane-1,3-diones
Financial support by the Deutsche Forschungsgemeinschaft (Ba 1372/23) and by the Elitenetzwerk Bayern (Internationales Doktorandenkolleg (IDK) Photo-Electro-Catalysis, Chemical Catalysis with Photonic or Electric Energy Input) (Ph.D. fellowship to J.H.) is gratefully acknowledged.
Abstract
When irradiated with visible light, various cyclic 2-alk-4-enyl-substituted 1,3-diketones undergo an intramolecular endo-addition (m = 1) onto the double bond resulting in spirocyclic products (11 examples, 62–92% yield). Both an organic (TXT: thioxanthone, 20 mol%) and an organometallic Ir-based photocatalyst (5 mol%) promote the reaction. Addition of triisopropylthiophenol is required to secure high yields. The spirocyclization of a 2-alk-5-enyl-substituted substrate (m = 2) delivers a mixture of the seven-membered endo- and the six-membered exo-cyclization products.
Supporting Information
- Supporting information for this article is available online at https://doi.org/10.1055/a-2004-3771.
- Supporting Information
Publication History
Received: 28 November 2022
Accepted after revision: 28 December 2022
Accepted Manuscript online:
28 December 2022
Article published online:
30 January 2023
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References and Notes
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Reviews:
Reviews on the [2+2] photocycloaddition:
Recent examples from our group:
For 6-endo-cyclization reactions observed under typical radical conditions, see:
Reviews: