Aromatic Meta Photocycloaddition

Aromatic Meta Photocycloaddition

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  • General Characteristics

Aromatic rings and alkenes undergo [3+2] cycloaddition under photo-irradiated conditions. This reaction provides complex fused ring skeletons that are otherwise difficult to obtain. Synthetically speaking, site-selective intramolecular versions are especially useful.

  • General References

<Photochemical reactions in total synthesis>

  • Reaction Mechanism

The reaction is considered to proceed via either the zwitterionic or biradical intermediate, with the α bond formation step being rate-determining. Since the product of competitive [2+2] cycloaddition is less stable, [3+2] cycloaddtion predominates.


  • Examples

The synthesis of retigeranic acid.[1]


  • Experimental Tips

  • References

[1] Wender, P. A.; Singh, S. K. Tetrahedron Lett. 1990, 31, 2517. doi:10.1016/0040-4039(90)80114-2

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