Imido radicals, reaction

The reaction presumably involves the C—H functionalization via a three-step sequence consisting of (i) oxidation of the Fe(II) catalyst to an Fe(lll) imido radical by the alkyl azide substrate, (ii) intra-molecular H-atom abstraction causing the formation of an alkyl radical and an Fe(in) amide (Path la), and finally (iii) radical recombination to form the observed V-heterocycUc product. An alternative direct C—H bond insertion (Path 11) by the Fe(III) imido radical cannot be ruled out. Both hypothesized mechanisms necessitate the alignment of substrate C—H bond to be in close proximity to the reactive Fe-imido radical. A conformation requiring the C—H bond substrate to approach the imido radical opposite the chloride ligand is expected to enable rapid C—H bond functionalization. With this potentially promising synthetic strategy, azetidines, pyrrolidines, and piperidines can be prepared. 

Scheme 68) <86H(24)1565>. The most likely mechanism of this reaction involves radical anion formation (414), cleavage, successive electron addition, and cyclization of the intermediary imido-ester (415) to an imidazole derivative (416) (Scheme 68). 

The dark green complex [Co PhB(Bu lm)3 NHBu ] can further react with a radical proton abstractor (a phenol radical) to form the corresponding cobalt(Ill)-imido complex in a redox reaction that is reported to model a cracial step in the oxidation of water to elemental oxygen in the catalytic system of photosystem II [406] (see Figure 3.131). A similar iron(III) complex exists as well [415]. 

Reductive oxidation of />-nitrotoluene to -aminobenzaldehyde, 31, 6 Reformatsky reaction, 37, 38 Reissert s compound, 38, 58 Reissert reaction, 38, 58 Replacement, benzenesulfonate groups by bromine atoms, 31, 82 bromine, by a thiol group, 30, 35 by fluorine, 36, 40 chlorine, by an amino group, 31,45 by a thiol group, 32, 101 by iodine, 30, 11 by methoxyl, 32, 79 by nitrile, 36, 50 in an imido-chloride group by an anilino group, 31, 48 chlorine and nitro by ethoxyl radicals, 32,68... 

The successful preparation of structural analogues of raised the hope that the chemistry of ammoxidation might also be reproduced in solution under mild laboratory conditions suitable for mechanistic studies. Thus we turned our attention to the critical C-N bond formation step to find out whether one can indeed produce ammoxidized product from a radical with a d imido metal center. For our studies diimido complexes (t-B iN)2M(OSiMe3)2 (M = Cr, Mo) [8,9] were selected as models for the postulated active sites in ammoxidation. Benzyl rather than allyl radicals were chosen for study since the products of allyl radical oxidation are not expected to be stable under our reaction conditions and because benzyl and allyl exhibit similar behavior in oxidation reactions [14]. Indeed, when a solution of (t-BuN)2M(OSiMe3)2 in toluene was heated at 100 C in the presence of benzoyl peroxide as a radical initiator, benzylidene-t-butylamine was obtained in up to 52% yield (Table I). The remaining organic products were C02> bibenzyl, and the expected isomeric distribution of (ortho meta para = 63 21 16) of methylbiphenyls. 

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