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Updated: Sep 9, 2025
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)
Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Synthesis of Cyclobutenoates from Photochemical Rearrangement of α-Diazo Cyclopropanes and Computational Studies
Raphaël Dollet1, Claude Y Legault2, Thomas Poisson1
1INSA Rouen Normandie, Univ. Rouen Normandie, Univ. Caen Normandie, ENSICAEN, CNRS, Normandie Univ., Institut CARMeN, Rouen, F-76000, France.
Abstract:
The ring expansion of α-cyclopropyl diazoacetates into cyclobutenoates upon irradiation at 425 nm was reported. This method allowed an access to a large array of cyclobutenoates as a mixture of regioisomers. The products were isolated in moderate to excellent yields (17% to 75%) and moderate to good regioisomeric ratio (55:45 to 82:18). The synthetic utility of the products was showcased and the mechanism was studied. Thanks to DFT calculations, the formation of two regioisomers was explained as well as the involvement of a singlet state carbene.
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