Diastereocontrol in [4+4]-photocycloadditions of pyran-2-ones: effect of ring substituents and chiral ketal

4-Mesyloxypyran-2-ones joined to furan by a three-carbon linker undergo intramolecular-crossed [4+4]-photocycloaddition with high or complete selectivity for the exo cycloadduct. When a C2-symmetric ketal was present on the tether adjacent to the pyranone ring, moderate levels of asymmetric induction were obtained.

Graphical abstractPhotochemical [4+4]-cycloadditions of 4-mesyloxypyran-2-ones with pendent furans occurred with high exo selectivity and displayed moderate diastereocontrol when substituted with a C2-symmetric ketal in the three-carbon tether ketal.Download full-size image