1-(2,3-Dihydro-5-benzofuranyl)ethanone is used to prepare tricyclic [1,2,4]triazine 1,4-dioxides as hypoxia selective cytotoxins. It is also used to synthesize N-(1-benzo[1,3]dioxol-5-yl)ethyl-, N-[1-(2,3-dihydro-benzofuran-5-yl)ethyl-, and N-[1-(2,3-dihydro-1H-indol-5-yl)ethylacrylamides with KCNQ2 opener activities.