An Efficient Flow-Photochemical Synthesis of 5H-Furanones Leads to an Understanding of Torquoselectivity in Cyclobutenone Rearrangements


  • Financial support from GlaxoSmithKline, the ERDF (IS:CE-Chem & InterReg IVa) and the EPSRC (including support for the Iridis cluster) are gratefully acknowledged. Rob Wheeler and Andy Craven are thanked for valuable advice.


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Go with the flow: 4-Hydroxycyclobutenones were efficiently transformed into 5H-furanones using an inexpensive flow-photochemical setup. The results challenge the notion that this and the related thermochemical rearrangement display torquoselectivity in their electrocyclic opening to a vinylketene intermediate. Selectivity in the photochemical rearrangement is due a dichotomous reactivity of the (E)- and (Z)-vinylketene intermediates (see scheme).