Carbonyloxy radicals

The thermal decomposition of thia2ol-2-yl-carbonyl peroxide in benzene, bromobenzene, or cumene affords thiazole together with good yields of 2-arylthiazoles but negligible amounts of esters. Thiazol-4-ylcarbonyl peroxide gives fair yields of 4-arylthiazoles, but the phenyl ester is also a major product in benzene, indicating reactions of both thiazol-4-yl radicals and thiazol-4-carbonyloxy radicals. Thiazole-5-carbonyl peroxide gives... 

Femtochemistry of Organic Peroxides Ultrafast Formation and Decarboxylation of Carbonyloxy Radicals... 

Fig. 3 Schematic potential energy diagram illustrating alternative decarboxylation pathways of carbonyloxy radicals Ri-COj. f(E) denotes the initial internal energy distribution of the carbonyloxy radical, k(E) is the specific rate constant for decarboxylation of the intermediate radical, AE denotes the energy separation of electronic ground and excited state of the carbonyloxy radical, and ArE is its dissociation energy into CO and product radical R(. For further details see Ref. [3].

Ferotochcmisiry of organic Peroxides 11 lira fast formation and decarboxylation of carbonyloxy radicals... 

Bis(ortfe-phenylphenylcarbonyloxy)iodo]benzene 667 and biphenyl-2-carboxylic acid 668 can be converted into 6/7-benzo[f]chromen-6-one in excellent yield via generation and cyclization of their corresponding carbonyloxy radicals 669 (Scheme 159) < 1997J(P 1)787, 1999J(P1)1713>. 

Shown in Fig. 2 are examples of two kinetic traces of transient absorbance difference which reflect formation and decarboxylation of carbonyloxy radicals after photo-induced decomposition of DINPO and TBNC. A detailed understanding of the kinetics is obtained from modeling the data. Within the experimental time resolution (150 fs), peroxide primary dissociation produces carbonyloxy radical intermediates, which decay either directly from an electronically excited state within about 500 fs or in a statistical unimolecular reaction on a ps to ps time-scale in the electronic ground state (see Fig. 3). In the case of DINPO photodissociation at 266 nm, the excited state of the 1-naphthylcarbonyloxy radical is too high energetically to be populated to any relevant extent.The reaction on the ground state PES can be treated by statistical unimolecular rate theory. 

Kita and coworkers have developed a simple and reliable method for the direct constmction of biologically important aryl lactones 573 from carboxylic acids 572 using a combination of PhI(OAc)2 with NaBr (Scheme 3.226). The mechanism of this reaction includes initial generation of carbonyloxy radical followed by intramolecular benzylic hydrogen abstraction and cycUzation [618]. 

Changing the structure of R affects the activity of monoperoxycarbonates as previously discussed for peroxyesters. The other cogenerated radical is an alkoxy-carbonyloxy radical. The nature of the R group has practically no effect on the reactivity of monoperoxycarbonates having the same 00-tert-aSky group. The 10-h half-life temperature remains at 100°C for almost all 00-fert-butyl 0-alkyl monoperoxycarbonates. 

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