Dioxetanes formation

The mechanism of 1,2-dioxetane formation in the reaction of lucigenin with hydrogen peroxide suggests a nucleophilic attack of peroxide anion on position 9 of the acri-dinium ring, followed by deprotonation and subsequent formation of 1,2-dioxetane ring... 

Dioxetanes, formation by 1,2-cycloaddition of singlet O2 81CSR205, 81T1825 79CRV359, 79MI8, 79MI10. 

Dioxetanes, formation from heterocycles 81CSR205, 81T825 79MI10. 

Further challenging work will be necessary to resolve the mechanism of 1,2-dioxetane formation. 

In these enzymic oxygenations no evidence exists that excited-state products are formed. In fact, 1,2-dioxetane intervention has not been soundly established, except that it constitutes a mechanistic convenience. The dioxygenase action entails cleavage of aromatic substrates [Eq. (34a)] or their cis-dihydroxylation [Eq. (34b)].91 A recent chemical model study on pyrocatechase discounts 1,2-dioxetane formation.92... 

The steering effect of the hydrogen bonding was applied to a highly diastereose-lective dioxetane formation from a chiral allylic alcohol (Scheme 21) [110]. 

In eukaryotes, such as mammals and fungi, epoxide hydrolases play a key role in the metabolism of xenobiotics, in particular of aromatic systems [30,31 ]. On the other hand, in prokaryotes (e.g. bacteria) these enzymes are essential for the utilization of alkenes as carbon-source. In general, aromatics can be metabolized via two different pathways (Scheme 5) (i) dioxetane formation via dioxyge-... 

Dimole absorption and emission, 247 Dioxetane formation, 253 Donor-acceptor energy levels, 201 property, energies of, 289 Dipole-dipole resonance energy transfer, 192, 193... 

In summary, a stereoselective 10-step total synthetic route to the antimalarial sesquiterpene (+)-artemisinin (1) was developed. Crucial elements of the approach included diastereoselective trimethylsilylanion addition to a,p-unsaturated aldehyde 16, and a tandem Claisen ester-enolate rearrangement-dianion alkylation to afford the diastereomerically pure erythro acid 41. Finally, acid 41 was converted in a one-pot procedure involving sequential treatment with ozone followed by wet acidic silica gel to effect a complex process of dioxetane formation, ketal deprotection, and multiple cyclization to the natural product (+)-artemisinin (1). The route was designed for the late incorporation of a carbon-14 label and the production of a variety of analogues for structure-activity-relationship (SAR) studies. We were successful in preparing two millimoles of l4C-l73 which was used for conversion to I4C-arteether for metabolism75 and mode of action studies.76,77... 

A highly diastereoselective dioxetane formation has been found in the oxygenation of the adamantylidene-substituted chiral allylic alcohol 126a (Sch. 71) [10b,128],... 

Dioxetane formation by 2 does not occur in lipids because it requires an electron-donating atom such as N or S next to the double bond (100). 

The catalytic mechanism for IDO and TDO is believed to proceed via the formation of a hydroperoxide at C-3 of the indole ring, followed either by dioxetane formation or Criegee rearrangement, as shown in Figure 26. Formation of the hydroperoxide could either take place via nucleophilic attack upon heme-bound dioxygen, or via the formation of an indole radical, followed by recombination with iron(III)-superoxide. The structure of human IDO was published in 2006. Site-directed mutagenesis of active site residues has established that Phe-226, Phe-227, and Arg-231 contribute toward catalysis. ... 

Despite a diligent search for evidence of dioxetane formation, no one has been able to verify the occurrence of this proposed reaction. Moreover, since benzaldehyde could not undergo this type of reaction, an alternate explanation which could also be applied to olefins was desirable. 

Oxetane (Paterno-Buchi reaction) and dioxetane formation... 

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