AbstractImidazo‐1,5‐alkynyl alcohol derivatives were synthesized, and they were cyclized to imidazo‐1,4‐oxazines by means of cesium carbonate. Propargyl‐allene isomerization was examined, and the reaction mechanism was proposed. Moreover, cytotoxicity of synthesized molecules against LN405 cell lines was investigated by means of structure‐activity relationship (SAR). With SAR study, toxicities of some functional groups have been shown. In addition, two lead compounds were tested against DNA damaging.