Electrophiles types

In aromatic substitution of the electrophilic type, a cation or potential cation attacks the benzene ring. The transition state or intermediate, whichever it may be, has largely covalent bonds holding... 

The discovery of carbene and carbenoid additions to olefins was the major breakthrough that initiated the tapping of this structural resource for synthetic purposes. Even so, designed applications of cyclopropane chemistry in total syntheses remain limited. Most revolve around electrophilic type reactions such as acid induced ring opening or solvolysis of cyclopropyl carbinyl alcohol derivatives. One notable application apart from these electrophilic reactions is the excellent synthesis of allenes from dibromocyclopropanes 2). 

The mechanism suggested in Ref. [129] does not imply the formation of an intermediate product with an open ring. Active oxaziridine-4a,5-flavin benzoxide formed from flavin hydroperoxide is assumed to be the intermediate. This mechanism based on the electrophilic type of the oxaziridine system is justified in multiple examples, united in the following diagram [128] ... 

The different kinetic behaviour of dienophiles, according to their substituents at the unsaturated bond, is illustrated in Table 7, by considering only carbon dienophiles (either of C=C or of C=C type). Two out of four dienes chosen are of the electron-rich type, and two of the electrophilic type Diels-Alder reactions of both kinds are therefore presented. 

The majority of substitution and addition reactions are of electrophilic type. Here aromatic compounds tend to undergo substitution for three reasons. 

Scheme 9 Proposed mechanism for the Catalytica system electrophilic-type mechanism for CH hydroxylation of CH4 catalyzed by the (bpym)PtCl2/H2S04...

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