Substituent effects on the decomposition of 1,2-dioxetanes

A CASSCF/CASPT2 approach to the decomposition of thiazole-substituted dioxetanone: Substitution effects and charge-transfer induced electron excitation

“…For instance, from 1,2-dioxetane to dioxetanone, we found both the geometrical transition state (TS) structure and the thermal electron excitation mechanism have been evidently changed -due to the change of the fragmenting species -while the quantum yields of the chemiluminescence does not increase [17][18][19]. In contrast, experiential studies have revealed that introducing aromatic electron-donating groups into dioxetane can significantly enhance chemiluminescence [20,21], and could possibly initiate intramolecular CIEEL/ CTIL process differing from the thermal decomposition of simple dioxetane but similar to what occurs in bioluminescence systems.…”

“…That is, the thiazole substitution does not evidently change the mechanism of the dioxetanone decomposition. Second, we noted that the geometries (of the key structures) and the activation energies of the OH-TDO is roughly the same as those of H-TDO, and the -OH substitution can neither alternate the reaction path nor invoke an ET process, therefore it does not account for the high-efficiency of the experimental observation [20,21]. Third, we observed that the -OH deprotonation dramatically change the nature of TS, i.e., the lowest-two singlet states both corresponding to ET states with significant contribution from the conjugated thiazole moiety, the concerted rupture of the O-O and C-C bonds, as well as the clearly reduced activation energy.…”

Singlet Oxygen as a Reagent in Organic Synthesis

“…In 1970, the irradiation of tetramethoxyethylene (7) sensitized by zinc tetraphenylporphine or dinaphthalenethiophene in an O 2 -saturated ether solution at À70 C led to the production of dioxetane 24 [19]. Purification was conducted by evaporating the In 1978, the photooxidation of 2,3-diphenyl-1,4-dioxene (8) was reported in CH 2 Cl 2 solution at À78 C [3,20]. Compound 8, when reacted with singlet oxygen from the irradiation of polymer-bound RB, afforded the corresponding dioxetane (1,6-diphenyl-2,5,7,8-tetraoxabicyclo[4.2.0]octane, 25) in 80% yield.…”

“…Bicyclic dioxetane 25 was insufficiently stable for combustion analysis. On the basis of 13 C NMR spectroscopy, the dioxetane structure was assigned [20]. 2,3-Di(2-anthryl)-1,4-dioxene (9) was also photooxidized in CH 2 Cl 2 solution at À78 C, and dioxetane 26 obtained in 51% yield [21].…”

Solid Materials as Sources for Synthetically Useful Singlet Oxygen

“…[9±13] Even unstable dioxetanes were readily prepared with PS-immobilized RB at low temperature, as in the oxygenation of 1,2-diaryl-pdioxenes, [14] Eq. (1).…”