Arenes => alkyl halides

In eontrast, dialkylhalonium salts sueh as dimethylbromonium and dimethyliodonium fluoroantimonate, whieh we prepared from excess alkyl halides with antimony pentafluoride or fluoroantimonie acid and isolated as stable salts (the less-stable chloronium salts were obtained only in solution), are very effective alkylating agents for heteroatom eompounds (Nu = R2O, R2S, R3N, R3P, ete.) and for C-alkylation (arenes, alkenes). 

Carbocations usually generated from an alkyl halide and aluminum chloride attack the aromatic ring to yield alkylbenzenes The arene must be at least as reactive as a halobenzene Carbocation rearrangements can occur especially with primary alkyl hal ides... 

The organic halide that reacts with the arene must be an alkyl halide (Section 12 6) or an acyl halide (Section 12 7)... 

Alkyl radical addition reactions to styrene chromium tricarbonyl can be accomplished using alkyl halides (10 equiv) and (TMSlsSiH (5 equiv) in the presence of AIBN in refluxing benzene, for 18 h (Reaction 66). " These reactions are believed to proceed through intermediates in which the unpaired electron is interacting with the adjacent arene chromium tricarbonyl moiety since the analogous reaction with styrene affords only traces of addition products. 

Alternatively, the Sn2 nucleophilic substitution reaction between alcohols (phenols) and organic halides under basic conditions is the classical Williamson ether synthesis. Recently, it was found that water-soluble calix[n]arenes (n = 4, 6, 8) containing trimethylammonium groups on the upper rim (e.g., calix[4]arene 5.2) were inverse phase-transfer catalysts for alkylation of alcohols and phenols with alkyl halides in aqueous NaOH solution to give the corresponding alkylated products in good-to-high yields.56... 

Electron-rich carbyne complexes can react at the carbyne carbon atom with electrophiles to yield carbene complexes. Numerous examples of such reactions, mostly protonations, have been reported [519]. Depending on the nucleophilicity of the carbyne complex, such reactions will occur more or less readily. The protonation of weakly nucleophilic carbyne complexes requires the use of strong acids, such as triflic [533], tetrafluoroboric [534] or hydrochloric acid [535,536]. More electron-rich carbyne complexes can, however, even react with phenols [537,538], water [393,539], amines [418,540,541], alkyl halides, or intramolecularly with arenes (cyclometallation, [542]) to yield the corresponding carbene complexes. A selection of illustrative examples is shown in Figure 3.25. 

Since different reactivity is observed for both the stoichiometric and the catalytic version of the arene-promoted lithiation, different species should be involved in the electron-transfer process from the metal to the organic substrate. It has been well-established that in the case of the stoichiometric version an arene-radical anion [lithium naph-thalenide (LiCioHg) or lithium di-ferf-butylbiphenylide (LiDTBB) for using naphthalene or 4,4 -di-ferf-butylbiphenyl (DTBB) as arenes, respectively] is responsible for the reduction of the substrate, for instance for the transformation of an alkyl halide into an alkyllithium . For the catalytic process, using naphthalene as the arene, an arene-dianion 2 has been proposed which is formed by overreduction of the corresponding radical-anion 1 (Scheme 1). Actually, the dianionic species 2 has been prepared by a completely different approach, namely by double deprotonation of 1,4-dihydronaphthalene, and its X-ray structure determined as its complex with two molecules of N,N,N N tetramethylethylenediamine (TMEDA). ... 

Silicon vapor reacts with alkanes, alkenes, alkynes, arenes, ketones, alkyl halides, and ethers to give mainly polymers (104). 

Alkylation with Alkenes. Besides alkyl halides, alkenes,86,148-151 alkynes,152 alcohols and ethers,86,151,153 and esters86,151,154 are most frequently used for alkylation of arenes. Of all alkylating agents, alkenes are practically the most important. 

When an alkene is used in the alkylation of arenes, metal halides with hydrogen halide or water as cocatalyst, protic acids, and acidic oxides can be used as catalysts. Both linear and cyclic alkenes are used in alkylations. Alkylation with alkenes is usually preferred in industry because the processes are simpler and olefins are readily and cheaply available in pure form from petroleum refining processes. 

Alan H. Haines, Methods for the Oxidation of Organic Compounds, Alcohols, Alcohol Derivatives. Alkyl Halides, Nitroalkanes, Alkyl Azides, Carbonyl Compounds, Hydroxyarenes and Amino-arene s, 1988... 

Table XXXVI is a list of some catalytic photochemical redox transformation of organic reactants by (Q or H)3PW 204o. In the presence of UV light, Q3PW12O40 reacts with paraffins, arenes, alcohols, alkyl halides, ketones, nitriles, thioethers, and water. Under either anaerobic or aerobic conditions, decarboxylation, dehydrogenation, dimerization, polymerization, oxidation, and acylation takes place.

Through the interaction of an alkylating agent, a hydrogen atom of the aromatic core, in the case of alkylation of arenes, is replaced by an alkyl group driven by a Friedel-Crafts catalyst. A variety of alkylating agents (e.g. alkyl halides, alcohols,... 

This Lewis acid-catalyzed electrophilic aromatic substitution allows the synthesis of alkylated products via the reaction of arenes with alkyl halides or alkenes. Since alkyl substituents activate the arene substrate, polyalkylation may occur. A valuable, two-step alternative is Friedel-Crafts Acylation followed by a carbonyl reduction. 

Benzyl methyl ether or allyl methyl ethers can be selectively metalated at the benzylic/allylic position by treatment with BuLi or sBuLi in THF at -40 °C to -80 C, and the resulting organolithium compounds react with primary and secondary alkyl halides, epoxides, aldehydes, or other electrophiles to yield the expected products [187, 252, 253]. With allyl ethers mixtures of a- and y-alkylated products can result [254], but transmetalation of the lithiated allyl ethers with indium yields y-metalated enol ethers, which are attacked by electrophiles at the a position (Scheme 5.29). Ethers with ft hydrogen usually undergo rapid elimination when treated with strong bases, and cannot be readily C-alkylated (last reaction, Scheme 5.29). Metalation of benzyl ethers at room temperature can also lead to metalation of the arene [255] (Section 5.3.11) or to Wittig rearrangement [256]. Epoxides have been lithiated and silylated by treatment with sBuLi at -90 °C in the presence of a diamine and a silyl chloride [257]. 

The metal-bound carbon atom in organopalladium(II) complexes can formally react either as an electrophile or as a nucleophile. Treatment of arylpalladium(II) complexes with alkyl halides, for example, yields products of homo- or cross-coupling, possibly via intermediate formation of hexacoordinated Pd(IV) complexes [31,33] (Scheme8.1). Treatment of the same type of complex with alkyl Grignard reagents or other carbon nucleophiles, on the other hand, also yields the corresponding alkyl arenes via nucleophilic displacement of a ligand followed by reductive elimination (Scheme 8.1). 

Ni(0)-Ni(I)-Ni(II) Catalysis Coupling Reactions of Alkyl Halides with Unsubstituted Arenes... 

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