Radical cyclopropyloxy

Now the second step. Make C7-N2. Break 01-N2, C5-C7. Heating the tricyclic compound causes thermolysis of the weak 01-N2 bond. The cyclopropyloxy radical quickly ring-opens to put the radical center at C7 then radical-radical recombination between C7 and N2 gives the product. 

A flavoprotein oxidase, which is also a methanol oxidizing enzyme, was inhibited by cyclopropanol 4 through the formation of a N-5 flavin adduct with a ring opened cyclopropyloxy radical [10]. 

A highly intriguing isomerization of the homoenolate radical which probably proceeds via formation of a cyclopropyloxy radical, was noted in the reaction of a mercurio aldehyde [37]. The product ratio should reflect the ratio of internal/ external trapping, and in fact the ratio of unrearranged and rearranged product depends on the concentration of the trapping reagent, Eq. (37). 

As Table 19 shows, the product composition resulting from metal ion oxidation is highly variable. The reaction course depends not only on the metal ion and its ligands, but also on the concentration and addition rate of the reactants. The key intermediates in these reactions are the (3-propionate radicals, e.g. 140, which may be formed from highly unstable cyclopropyloxy radicals. The radical 140 has, in fact, been observed and characterized by ESR upon reaction of 1-methoxycyclopropanol with ceric sulfate.112 ... 

The second possible pathway (route b. Scheme 8) involves an intramolecular migration of the formyl group in what is commonly thought of as a two-step process. The first step involves an intramolecular radical addition to the carbonyl carbon to form an intermediate cyclopropyloxy radical (shown in Scheme 8 as TS 8—>8 ). The three-membered ring can then undergo a ring-opening... 

Alkoxy radicals for ring expansion can be generated from alcohols by oxidative methods such as hypohalite thermolysis/photolysis [19a] and lead tetraacetate oxidation [19b], or peroxide reduction [19c]. The recent development of the hyper-valent organoiodine reagent (diacetoxyiodo)benzene (DIB) provides another way for efficient generation of alkoxy radicals (Scheme 11) [19d]. Additional oxidative methods to prepare cyclopropyloxy radicals include reaction of tertiary cyclopropanols or their silyl ether derivatives with various reagents such as manganese(III) tris(pyridine-2-carboxylate) [Mn(pic)3] [20a], Fe(III) salts [20b], and vanadyl ace-tylacetate [20c] (Scheme 12). 

Small-ring radical opening is a facile process. This process has been incorporated in the zero bridge cleavage of strained bicycles for one- and two-carbon ring expansions (Scheme 14). Ring expansions of cyclopropyloxy and cyclobutyloxy radicals have been discussed in the previous section. This section focuses on cyclopropyl-carbinyl, ot,j8-epoxyalkyl and cyclobutylcarbinyl radicals. 

Of possible biological interest is the report, based on a model reaction study with hydroxocobalamine, that the coenzyme-B, 2-dependent methyl-malonyl-CoA mutase reaction could involve intramolecular addition of a primary radical to a thioester group. The cyclopropyloxy radical so formed in a Cy3/Cy4 case would open to the carbethoxy-substituted and hence stabilized radical to give the rearranged product. ... 

The cyclopropyloxy radical intermediate fragments in this fashion because the resulting tertiary radical is stabilized via the resonance effect excerted by the adjacent carbonyl group of the ester. 

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