Photochemistry of alkenyl- and acetal-substituted pyridines

Ethyl 3-(2-pyridyl)propionate formation results from irradiation of 3-(2-pyridyl)propanal diethylacetal in acetonitrile. This photoreaction is unique to the heteroaromatic pyridine and only occurs in acetonitrile. A minor product, 1-aza-2-methyl-3-(2-ethanal diethylacetal)-4-ethoxycycloocta-1,3,5,7-tetraene, is also obtained. The irradiation of 2-methyl-6-(2-pyridyl)-2-pentene in the presence of various sensitizers results in addition to the alkene side-chain to produce oxetanes.