Electrophiles allylation

Oompound 1, 2-(hydroxymethyl )a11y1trimethylsilane, represents a conjunctive reagent which can be considered as the equivalent of zwitterion 2, possessing a nucleophilic allyl anion synthon and an electrophilic allyl... 

The geometry of electrophilic allylic rearrangement has not been studied very much (cf. the nucleophilic case, p. 422), but in most cases the rearrangement takes... 

Electrochemistry (Continued) purely organic compounds, 342 sulfide oxidation, 361 Electrode materials, 342 Electrophilic allylation, 192 attractive interaction, 196 mechanism, 192, 197 turnover-limiting step, 197 Electroreaction, asymmetric, 342 Electrostatic interaction, 328 Elimination and insertion, 3 Enamide reactions ... 

Vinyl epoxides react with Pd(0) to yield electrophilic allyl complexes which can convert alcohols and phenols into allyl ethers (Scheme 4.80). These alkylations usually yield 2-alkoxy-2-vinylethanols, and if the Pd-mediated etherification is performed in the presence of a chiral, enantiomerically pure diphosphine, enantiomeri-cally enriched ethers may be obtained (Scheme 4.80) [356, 357]. 

For Pd-catalyzed cross-coupling reactions the organopalladium complex is generated from an organic electrophile RX and a Pd(0) complex in the presence of a carbon nucleophile. Not only organic halides but also sulfonium salts [38], iodonium salts [39], diazonium salts [40], or thiol esters (to yield acylpalladium complexes) [41] can be used as electrophiles. With allylic electrophiles (allyl halides, esters, or carbonates, or strained allylic ethers and related compounds) Pd-i73-jt-allyl complexes are formed these react as soft, electrophilic allylating reagents. 

In essence, the ideology of this synthesis is similar to that employed in the Robinson annulation. In fact, here again the carbanionic intermediate 99 (formed upon the initial addition of arylmagnesium cuprate reagent 100 at the double bond of Michael acceptor 98) is treated with a carbon electrophile (allyl bromide) to give the final adduct 97 with two new C-C bonds. The only essential difference lies in the fact that the quenching of the enolate intermediate 99 with the electrophile occurs as an intermolecular reaction (in contrast to the Robinson annulation where this step proceeds intramolecularly). 

Enantioselective electrophilic allylation of 2-acetamido-malonate esters is effected by a BINAP-Pd complex (eq 24). ... 

Most electrophilic allylic rearrangements involve loss of hydrogen, but they have also been observed with metallic leaving groups. Sleezer, Winstein, and Young found that crotylmercuric bromide reacted with HCl 10 times faster than n-butyl-mercuric bromide and the product was >99% 1-butene. " These facts point to an SeI mechanism (lUPAC designation cyclo- l >ID k nk ... 

The most general formation of electrophilic cyclopropanes involving nucleophilic attack on electrophilic allyl halides occurs when sodium borohydride and sodium or potassium cyanide is used as a nucleophilic species (equation... 

The reaction of electrophilic allyl halides with active methylene functions give a completely different course although intermediate electrophilic cyclopropanes (327) play a crucial role. Ring-opening of the cyclopropanes affords compounds 328 in which the electron-withdrawing groups are rearranged to the allylic position (equation 102) . This... 

TABLE 2. Rate constants for the cyclopropanation reactions of electrophilic allyl halides... 

Isopentenyl diphosphate isomerase (IPI E.C. 5.3.3.2) catalyzes the isomerization of isopentenyl diphosphate (IPP) to dimethylallyl diphosphate (DMADP), a previous and mandatory step to create the electrophilic allylic diphosphates needed for the condensation reaction generating geranyl diphosphate, Fig. (6). Thus, IPI is an essential enzyme in organisms which synthesize IPP through the mevalonic acid pathway as archaea, eukaryota and some Gram-positive bacteria [275, 305]. 

The Houk conformation for reactions ofalkenes with electrophiles Allyl silanes... 

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