Hetero-staged reaction mechanism

The disadvantages of this model are evident—it cannot account for the impact of the intervalent reactions kinetics to the total electrochemical process. That this impact is significant and cannot be ignored was substantiated earlier in the works of Kozin and co-authors summarized in their book [35]. In order to allow for the contribution of the intermediates, the so-called hetero-staged reaction mechanism was proposed, in contrast to Vetter s mechanism defined there as the homo-staged one [34]. 

However incorporating the accompanying reactions with intermediate compounds, this hetero-staged mechanism is still tmcertain, arbitrary and thus unsatisfactory and non-system like. Hence, the next step is obvious—it is the attempt to develop the systematic approach by synthesis of the two considered mechanisms. 

E) The understanding of the reaction mechanism makes it possible for them to make a bold assumption. As can be seen from Fig. 6.3, all the reactions of aroyl- and alkanoylquinoxalines when interacting with 1,2-DABs at the initial stage behave as hetero analogues of a-diketones, that is, as iminoketones (see Sects. 6.4 and 6.10). Then there arises the problem, why other quinoxaline derivatives with certain substituents do not behave like a-haloketones 49 (see Sect. 6.5), P-diketones 50 (see Sect. 6.6), a-aminoketones 51 (see Sect. 6.7), methyl ketones 52 (see Sect. 6.8), aromatic o-aminoaldehydes (or ketones) 53 (see Sect. 6.9), etc. 

Many of the Diels-Alder type reactions may be described in terms of hetero-lytic mechanisms, some of which involve electrophilic attack as the first stage. The evidence for such mechanisms is, as yet, incomplete and such additions are discussed in Chapter 2. 

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