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 (λmaxCL) 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.

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