Intramolecular Photocycloadditions of 1-(ω-Alkenyl)-2-pyridones Possessing an Ester Group on the Olefinic Carbon Chain

Article abstract of DOI:10.1021/jo00047a025

Photochemical reactions of three kinds of 1-(ω-alkenyl)-2-pyridones 1-8 were investigated.Photosensitized cyloadditions of 1-(ω-alkenyl)-2-pyridones and 1,3-bis(ω-alkenyl)-2-pyridone 2-6 afforded intramolecular <2 + 2>cycloadducts across the 5,6-bonds of the 2-pyridones to give the tricyclic lactams 14-18: the additions were site-, regio-, and stereospecific.The yields of the adducts diminished in proportion to increased side-chain length.The one possessing the shortest alkenyl group, 1, and the 1-<ω-(acryloyloxy)alkyl>-2-pyridones 7 and 8, however, gave no products.On the other hand, direct irradiation of 3 afforded a bicyclic lactam 19.The intramolecular cycloaddition mechanism was discussed in terms of the excited state of 2-pyridone, as calculated by MNDO-CI method.