Base-induced chemiluminescence of 5-tert-butyl-1-(4-hydroxybenz[d]oxazol-6-yl)-4,4-dimethyl-2,6,7-trioxabicyclo[3.2.0]heptanes: chemiluminescence–chemiexcitation profile in aqueous medium

Bicyclic dioxetanes bearing a 2-aryl-4-hydroxybenz[d]oxazol-6-yl moiety (3a–3c) and their 2-alkyl-analogs (3d, 3e) were synthesized. All these dioxetanes (3a–3e) afforded light with high efficiency on treatment with tetrabutylammonium fluoride in acetonitrile. In the NaOH–H2O system, chemiluminescence efficiency (ΦCIEEL) for alkyl-analogs (3d, 3e) decreased markedly, while ΦCIEEL for 3a–3c was still considerably high. Fluorescence study revealed that the marked decrease of ΦCIEEL for alkyl-analogs would be attributed to a synergetic effect of decreased chemiexcitation yield and fluorescence yield of the emitter in NaOH–H2O system.