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Related Reactions
Synthesis of oxetanes

Paterno-Büchi Reaction

The photochemical [2+2] cycloaddition of a carbonyl with an olefin to give an oxetane.

Mechanism of the Paterno-Buechi Reaction

The possible transitions (C=O) are shown below:

Once the carbonyl ground state has been photoexcited, either a singlet or triplet state may be formed:


Either type of transition (n,π* and π,π*) and electronic state (singlet, triplet) may participate in the first stage of this reaction, which is rationalized by invoking diradical intermediates:

Breaking of the new σ-bonds requires more energy, and the reverse reaction is not possible using same light frequency.

Recent Literature

The photocatalytic reactions of benzoylformate esters with alkenes can be directed toward either Paternò-Büchi cycloadditions or allylic functionalization reactions under conditions favoring energy transfer or electron transfer, respectively.
J. Zheng, X. Dong, T. P. Yoon, Org. Lett., 2020, 22, 6510-6515.

Paternò-Büchi Reactions of Silyl Enol Ethers and Enamides
F. Vogt, K. Jödicke, J. Schröder, T. Bach, Synthesis, 2009, 4268-4273.