Alkylation, of olefins

Figure 4-13. Liquid-liquid heterogeneous tubular flow reaotor (e.g., alkylation of olefins and Isobutane). (Source J. M. Smith, Chemloal Engineering KInetlos, 3rd ed., McGraw-Hill, Inc., 1981.)...

The alkylation proceeds with aluminum chloride or hydrofluoric acid as catalyst, by which the importance of aluminum chloride diminishes. Today approximately 70% of all manufacturers use the HF process [4]. In addition, LAB is produced by the alkylation of secondary chloroparaffins (Wibarco in Germany) and by the alkylation of olefins (EniChem Augusta in Italy) over an aluminum chloride catalyst [12]. 

The alkylation of olefinic G-H bonds proceeds when conjugated enones are employed in the ruthenium-catalyzed reaction with alkenes, as shown in Equation (16).1 7 Among the acylcyclohexenes, 1-pivaloyl-l-cyclohexene exhibits a high reactivity and the presence of an oxygen atom at the allylic position in the six-membered ring increases the reactivity of the enones. Some terminal olefins, for example, triethoxyvinylsilane, allyltrimethylsilane, methyl methacrylate, and vinylcyclohexane, are applicable for the alkylation of the olefinic C-H bonds. Acyclic enones also undergo this alkylation. 

The photochemical alkylation of olefins by nitriles and ketones is not straightforward, due mainly to the inefficient abstraction of hydrogen from an electron-withdrawing-substituted carbon by an electrophile such as the photocatalyst excited state. Nevertheless, various methyl ketones have been synthesized by the irradiation of a ketone/oleftn mixture dissolved in aqueous acetone. The mechanism of the reaction remains to be clarified, but a water-assisted C—C coupling between an acetonyl radical and the olefin has been postulated (Scheme 3.12). The reaction has several advantages, as it is cheap (an acetone/water mixture is used as the solvent) and occurs under mild metal-free conditions with no need for a photocatalyst [28],... 

Conjugate reductions and Michael alkylations of olefinic nitriles are found in Section 74D (Alkyls from Olefins). 

For the alkylation of olefinic ketones, see also Section 177 (Ketones from Ketones), and Section 74E (Alkyls from Olefins) for conjugate alkylations. 

Intramolecular alkylation of olefins has been investigated extensively, perhaps because it might be synthetically more useful than the intermolecular version, because the regiochemical issue of both reacting electrophile and accepting olefin should less frequently arise. Intramolecular acylation of carbon-carbon double bonds, which is still a convenient method for the preparation of carbocyclic skeletons, has been con-... 

Table 19. The Friedel-Crafts type alkylation of olefins and acetylenes. Substrate Titanium sail Product...

For most organic syntheses the reaction does not need to be considered since the structures and conditions must be such as to prevent other transformations and to favor this interchange. It is, however, one of the essential steps in the alkylation of olefins (p. 143) and the isomerization of alkanes (p. 59). 

Conversely, however, it is important to notice that the order of re-activity of carbonium ions once they are formed is just reversed. We find, for example, in the isomerization of alkanes (p. 59) and in the alkylation of olefins (p. 143) that a primary or secondary carbonium ion extracts a hydrogen atom with a pair of electrons from an alkane so as to form a secondary or tertiary carbonium ion. For many carbonium ion transformations formation of the ion seems to be the rate-controlling step of the process. The Wagner-Meerwein rearrangement (p. 56) appears to be an exception to this rule. 

Abstraction of a hydrogen atom together with a pair of electrons from a saturated hydrocarbon. This reaction has already been mentioned (p. 40) and will be discussed again under the Alkylation of Olefins (p. 143) and the Isomerization of Alkanes (p. 59). 

Other sources of olefins, such as a-olefins, can also be used to produce LAB. In most cases, these are only used as a supplemental feedstock to alkylation units, as a means of boosting LAB production. Typically, economics preclude the use of purchased olefins as the sole feedstock for the production of LAB. Benzene is another feedstock required for the alkylation of olefins to produce alkylbenzenes. 

During alkylation, some undesirable side reactions occur. A couple of these side reactions are outlined in Fig. 7. These secondary reactions include alkylation of olefin with LAB to form dialkylbenzenes, and the reaction of two olefins to form a dimer. 

Tab. 3.23 Titanocene-catalyzed double alkylation of olefins with alkyl bromides...

Catalytic Enantioselective Alkylation of Olefins with Alkylmagnesium Halides... 

The radical mechanism is possible in the addition of silicon organic compounds to olefins (247) and in the alkylation of olefins by paraffins under high pressure on AI2O3 (248) [for the beginning of this work, see Freidlin et al. (249-253)]. Since such reactions result in the formation of radicals, chain reactions are possible. Surface chains in catalytic reactions are probable in syntheses from water gas (254) and the hydrocondensation of CO with olefins (255, 256). 

Alkylation of olefins. 1-Alkenes (and 1,2-disubstituted alkenes) can be alkylated primarily at the 2-position by stabilized carbanions in the presence of this Pd(II) complex and triethylamine. The reaction involves a palladium complex of the alkenc followed by 8-elimination of Pd(0) to give the unsaturated product, which can be hydrogenated if desired before work up. ... 

Alkylation of olefins with isobutane to gasoline AICI3 Ipatieff, Pines, 1932... 

Nucleophilic attack of stabilized carbon nucleophiles on coordinated olefins is also known. Hegedus developed the alkylation of olefins shown in Equation 11.31. The (olefin)palladium(II) chloride complexes did not react with malonate nucleophiles, but the triethylamine adduct does react with this carbon nucleophile to provide the alkylation product. This reaction has recently been incorporated into a catalytic alkylation of olefins by Widenhoefer. - Intramolecular reaction of the 1,3-dicarbonyl compounds with pendant olefins in the presence of (GHjCNl PdCl occurs to generate cyclic products containing a new C-C bond (Equation 11.32). Some intermolecular reactions with ethylene and propylene have also been developed by this group. Deuterium labeling studies (Equation 11.32) have shown that the addition occurs by external attack on the coordinated olefin. ... 

Dimerization, Telomerization, Polymerization, and Alkylation of Olefins. Reactions of alkenes and dienes are of tremendous interest and ionic liquids offer new possibilities in this field too (282,283). 

Use of strongly anionic nucleophiles such as alkylmagnesium halides and lithium alkyls leads to reductive dimerization or displacement of the olefin. It is quite possible however that alkylation of olefin-iron cations (IX) would be feasible with alkyl derivatives of zinc, cadmium, or tin reagents. Alkylation of dienyliron cations with dialkylzinc and dialkylcadmium reagents has recently been demonstrated (Section III,A,4). Alkylation of olefin-iron cations can be achieved under mild conditions with cr-bonded allyliron compounds [Eqs. (9) and (10), (Rosan et ai, 1973)]. 

Octene trimers are the main products of the 1-octene oligomerization in the presence of the system TiCl4-Et3Al2Cl3, and ZrCU modified with AICI3 oligomerizes 1-decene to trimers and tetramers with a yield of 93% [944]. All of these titanium and zirconium catalysts have one deficiency they promote alkylation of olefins with aromatic solvents [944]. 

This section lists examples of the conversion R2C=CR2 — R2CH2. Fof the hydrogenation, dimerization and alkylation of olefins see section 74 (Alkyls, Methylenes and Aryls from Olefins)... 

Scheme 113) and the isoquinuclidines (253) from (252) (Scheme 114) since (250) and (252) were derived from the same starting material, these palladium-catalysed alkylations of olefins provide ready approaches to the ring systems of... 

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