N-Acyl group-directed color modulation in the t-BuOK-mediated chemiluminescent decomposition of hydroxyaryl-substituted dioxetanes fused with a pyrrolidine ring

Bicyclic dioxetanes, 1-(hydroxyaryl)-2-aza-6,7-dioxabicyclo[3.2.0]heptanes, bearing a syn-N-acyl or anti-N-acyl group underwent TBAF (tetrabutylammonium fluoride)-induced decomposition in DMSO or THF accompanied by the emission of bright light, the maximum wavelengths ( λ max CL ) of which were similar to each other. On the other hand, upon treatment with t-BuOK in THF, the dioxetanes bearing a syn-N-acyl group emitted light that showed a dramatic red-shift compared to that in a TBAF/THF system, while the dioxetanes bearing an anti-N-acyl group showed light with a blue-shift. For oxidoaryl-substituted dioxetanes bearing a syn-N-acyl group, t-BuOK most likely coordinated with both a syn-N-acyl and an oxygen of the dioxetane ring, so that two imide carbonyls in the produced emitter possessed a considerably regulated structure leading to a red-shift in the chemiluminescence. Such coordination of K+ was hardly expected for the case of the dioxetanes bearing an anti-N-acyl group, for which the strong contact of K+ to an oxidoaryl group presumably caused a blue-shift in chemiluminescence.