Photoaddition reactions between 1,2-dicarbonyl compounds and silyl enol ethers in acetonitrile and benzene were explored. Irradiation of acetonitrile or benzene solutions containing 1,2-diketone, acenaphthalquinone, phenanthrene-quinone and silyl enol ethers is observed to promote the production of 1,4-dioxenes, oxetanes, and ${eta}$-hydroxyketone by the [4+2]-cycloadditon, Paterno-Buchi processes, and SET promoted Claisen-type condensation. Among these competitive pathways leading to the generation of each types of products, SET promoted 1,4-dioxene and ${eta}$-hydroxyketone formation are more favored regardless of solvent polarity.