Irradiation of 1,4-diphenylbutadiyne (DPB) with a mixture of electron-deficient and electron-rich olefins in deaerated tetrahydrofuran yields a 1 : 1 primary photoadduct between DPB and electron-deficient olefins. Irradiation of the primary photoadduct of DPB and dimethyl fumarate (DMFu) with various olefins such as DMFu, acrylonitrile (AN), and 2,3-dimethyl-2-butene (DMB) in deaerated tetrahydrofuran yields regiospecific 1 : 1 photoadducts. The electron-deficient olefins are more reactive than electron-rich olefins in the photoreaction which proceeds through excited triplet state.