Photoinduced three-component reactions between tetracyanobenzene (TCNB), an alkene and water or a diol (as nucleophile) are initiated by electron transfer from the alkene to ¹TCNB* and proceed via a photo-NOCAS reaction sequence by nucleophilic capture of the alkene cation radical and subsequent radical pair coupling of the resulting radical with TCNB anion radical with concomitant cyanide anion extrusion. These photo MCRs provide simple one pot access to isocoumarins and precursors of larger ring lactones with diversified structural features.