Cyclodextrin mediated solvent-free enantioselective photocyclization of N-alkyl pyridones

Irradiation of N-methyl pyridone and N-ethyl pyridone included in β-cyclodextrin yields the photocylized product, chiral 2-azabicyclo[2.2.0]-hex-5-en-3-ones, in ∼60% enantiomeric excess. The inclusion complex is readily made by mechanically mixing the host β-cyclodextrin and the guest pyridone.