Electrophilic reactions benzylation

Arasabenzene, with chromium, 5, 339 Arcyriacyanin A, via Heck couplings, 11, 320 Arduengo-type carbenes with titanium(IV), 4, 366 with vanadium, 5, 10 (Arene(chromium carbonyls analytical applications, 5, 261 benzyl cation stabilization, 5, 245 biomedical applications, 5, 260 chiral, as asymmetric catalysis ligands, 5, 241 chromatographic separation, 5, 239 cine and tele nucleophilic substitutions, 5, 236 kinetic and mechanistic studies, 5, 257 liquid crystalline behaviour, 5, 262 lithiations and electrophile reactions, 5, 236 as main polymer chain unit, 5, 251 mass spectroscopic studies, 5, 256 miscellaneous compounds, 5, 258 NMR studies, 5, 255 palladium coupling, 5, 239 polymer-bound complexes, 5, 250 spectroscopic studies, 5, 256 X-ray data analysis, 5, 257... 

Electrophilicity of benzylating and alkylating reagents in Friedel-Crafts reactions... 

Bu3SnSMe, BF3-Et20, toluene, -20°C to 0°C, 1.5h H3O+, 70-97% yield. The intermediate stannanes from this reaction, when treated with various electrophiles, form benzyl and MEM ethers, benzoates, and tosylates, and when treated with PCC, they form aldehydes. ... 

Friedel- Crafts reactions. Benzyl ethers are activated by FeCls to react with arenes to provide diarylmethanes. A-Tosyhmines and aziridines also become electrophilic toward electron-rich arenes. ... 

As mentioned earlier, oxazolines can be hydrolyzed in the presence of strong bases to the corresponding N-(2-hydroxyethyl)amides, and also can react with weak electrophiles like benzyl bromide or allyl chloride to give poly(N-acylethyleneimines). Therefore, if the etherification reaction is... 

Step 3 Make a new bond between a nucleophile and an electrophile. Reaction of the 3° benzylic carbocation intermediate (an electrophile) with methanol (a nucleophile) forms an oxonium ion. 

Section 11 16 Addition reactions to alkenylbenzenes occur at the double bond of the alkenyl substituent and the regioselectivity of electrophilic addition is governed by carbocation formation at the benzylic carbon See Table 11 2... 

SuIfona.tlon, Sulfonation is a common reaction with dialkyl sulfates, either by slow decomposition on heating with the release of SO or by attack at the sulfur end of the O—S bond (63). Reaction products are usually the dimethyl ether, methanol, sulfonic acid, and methyl sulfonates, corresponding to both routes. Reactive aromatics are commonly those with higher reactivity to electrophilic substitution at temperatures > 100° C. Tn phenylamine, diphenylmethylamine, anisole, and diphenyl ether exhibit ring sulfonation at 150—160°C, 140°C, 155—160°C, and 180—190°C, respectively, but diphenyl ketone and benzyl methyl ether do not react up to 190°C. Diphenyl amine methylates and then sulfonates. Catalysis of sulfonation of anthraquinone by dimethyl sulfate occurs with thaHium(III) oxide or mercury(II) oxide at 170°C. Alkyl interchange also gives sulfation. 

Rates that are independent of aromatic substrate concentration have been found for reaction of benzyl chloride catalyzed by TiCl4 or SbFj in nitromethane. This can be interpreted as resulting from rate-determining formation of the electrophile, presumably a benzyl cation. The reaction of benzyl chloride and toluene shows a second-order dependence on titanium tetrachloride concentration under conditions where there is a large excess of hydrocarbon. ... 

In general the Stork reaction gives moderate yields with simple alkyl halides better yields of alkylated product are obtained with more electrophilic reactants such like allylic, benzylic or propargylic halides or an a-halo ether, a-halo ester or a-halo ketone. An example is the reaction of 1-pyrrolidino-l-cyclohexene 6 with allyl bromide, followed by aqueous acidic workup, to yield 2-allylcyclohexanone ... 

Merck s thienamycin synthesis commences with mono (V-silylation of dibenzyl aspartate (13, Scheme 2), the bis(benzyl) ester of aspartic acid (12). Thus, treatment of a cooled (0°C) solution of 13 in ether with trimethylsilyl chloride and triethylamine, followed by filtration to remove the triethylamine hydrochloride by-product, provides 11. When 11 is exposed to the action of one equivalent of tm-butylmagnesium chloride, the active hydrogen attached to nitrogen is removed, and the resultant anion spontaneously condenses with the electrophilic ester carbonyl four atoms away. After hydrolysis of the reaction mixture with 2 n HC1 saturated with ammonium chloride, enantiomerically pure azetidinone ester 10 is formed in 65-70% yield from 13. Although it is conceivable that... 

Accordingly, there have been numerous studies on the stereochemistry of these a-sulfinyl carbanions56-77. Representative data on the reactions of a-lithiosulfoxides derived from benzyl sulfoxides with some electrophiles are listed in Table 13. Although the stereochemistry depends on the substituent on the sulfinyl function, the diastereomeric ratio remains the same regardless of the electrophile used for each sulfoxide. 

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