Photocycloaddition of 6-chloro-1,3-dimethyluracil to olefins

Photoreaction of 6-chloro-1,3-dimethyluracil (6-ClDMU) with olefins having alkyl, alkoxy, and vinyl groups in acetone afforded the corresponding cyclobutapyrimidine derivatives with head-to-tail regiochemistry in appreciable yields, while the reaction with olefins bearing electron withdrawing groups gave no cycloadduct. Similar Photolysis of 6-ClDMU with phenylacetylene gave [2+2] cycloadduts, 3,5-diaza[4.2.0]oct-7-enes and diphenylquinazolines.