Alkylation by olefins

Enamines are readily alkylated by olefins activated by electron-withdrawing substituents. N Alkylation by one of these olefins is reversible, whereas C alkylation is not, so that a good yield of monoalkylated product is the rule. 

The acid-catalyzed reactions of olefin polymerization and aromatic alkylation by olefins have been very well explained by the carbonium ion mechanism developed by Whitmore (21). This mechanism provides the basis of the ensuing discussion, which is devoted to the application of such concepts (7,17) to catalytic cracking systems and to the provision of much added support in terms of recently developed structural energy relationships among hydrocarbons and new experimental evidence. 

Alkylation of benzene by an olefin occurs when the olefin is stirred with a cold mixture of benzene and sulfuric acid. The type of product formed depends upon the concentration of sulfuric acid high concentrations (90—%%) are required for alkylations. Alkylation by olefins is also catalyzed by aluminum chloride, ferric chloride, silicophos-phoric acid, and hydrogen fluoride. The last catalyst is the best of four studied for the preparation of phenylcycloheptane from benzene and cycloheptene. ... 

Herscovici, J, Muleka, K, Boumaiza, L, Antonakis, K, C-glycoside synthesis via glycal alkylation by olefinic derivatives, J. Chem. Soc., Perkin Trans. 1, 1995-2009, 1990. 

Alkali salts of carboxylic acids that have a C-H bond at the -position to the carboxyl group can be alkylated by olefins at 150-200° and 60-200 atm in the presence of sodium potassium, sodium hydride, or sodamide 8... 

Kunze, K.L., B.L.K. Mangold, C. Wheeler, H.S. Beilan, and P.R. Ortiz de Montellano (1983). The cytochrome P-450 active site. Regiospecificity of the prosthetic heme alkylation by olefins and acetylenes. J. Biol. Chem. 258, 4202-4207. 

The only structural requirement for prosthetic heme alkylation by olefins is a monosubstituted double bond. Accordingly, ethylene, but not ethane, is able to destroy the P450 heme while... 

Aluminum chloride catalyzes many alkylations. Parafiins, benzene, toluene, and xylenes are alkylated by olefins and cyclopropane in the presence of aluminum chloride. Usually hydrogen chloride is needed as a promoter (see Alkylate for the Petroleum Industry). 

Dioxolane, the cyclic ethylene glycol acetal of formaldehyde, is also alkylated by olefins under free-radical conditions. Here, it is the CH2 group between the two oxygen atoms that is the preferred site of hydrogen abstraction. 

Many additional routes to metal-alkyl complexes other than transmetallation and alkylation are discussed in later chapters of this text. For example, metal-alkyl complexes are generated by insertion of an olefin into a metal-hydride or or metal-hydrocarbyl species. Such insertion reactions are discussed in Chapter 9, but an example of the synthesis of a zirconium alkyl by olefin insertion into a zirconium hydride is shown in Equation 3.9. Metal-alkyl complexes are also generated by nucleophilic attack on coordinated olefins (Equation 3.10) or carbene ligands (Equation 3.11). These reactions are presented in detail in Chapter 11. 

In their extensive survey [141], devoted to methods of catalsdic synthesis of alkylphenols, N. I. Shuikin and E. A. Viktorova cite numerous literature data on the reactions of alkylation of phenol by olefins, alcohols, and alkyl halides, hi practice, methods of alkylation by olefins and alcohols have received wide circulation. 

It is of interest to note that in several instances the effect of a catalyst such as aluminum chloride or boron fluoride is enhanced by the presence of an acidic assistant. Alkylation by olefins with aluminum chloride as a catalyst is favored by the presence of anhydrous hydrogen chloride, and the condensation of primary alcohols with benzene uting boron fluoride is possible only with the aid of an. assistant such as phosr phoric anhydride, benzenesulfonic acid, or sulfuric acid. It has been foimd also that chlorides of tin, silicon, or titanium increase the catalytic activity of aluminum chloride, whereas ferric chloride decreases the... 

Naphthalene can be alkylated by olefins. Alkylation of naphthalene with propylene with solid phosphoric acid, perfluorinated alkane-sulfonic acids (C10F21SO3H and Ci2F25S03H) and Nafion-H is patented. 

In all the examples of acid catalysis considered in this chapter the characteristic effect of the acid catalyst is the increase in concentration of the acid group involved in the reaction. This is usually accomplished by the familiar displacement of one acid by another. In a few reactions displacement does not result, but the combination of the acid with the reacting substance merely localizes the electron deficiency on one atom, which can then behave as an acid. One example is the alkylation by olefins. 

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