Low-temperature singlet oxygenation of 1-alkoxy-1-aryl-2,2-diisopropylethylenes (9) gives the corresponding 1,2-dioxetanes (10) in high selectivity. Dioxetanes (10) are thermally stable enough to permit handling at room temperature, though an alkoxy group affects significantly their thermal stability and the order of half-life is MeO < EtO < i-PrO tert-BuO. On treatment with tetrabutylammonium fluoride in DMSO, dioxetanes (10e - 10h) bearing a m-siloxyphenyl decompose rapidly to emit intense blue light with Φ C L > 0.2. For the base-induced decomposition of 10e - 10h, the order of rate of decomposition is MeO < EtO < i-PrO < tert-BuO.