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:

n,π*-transition

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

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