Aluminum complexes ethers

With propene, n-butene, and n-pentene, the alkanes formed are propane, n-butane, and n-pentane (plus isopentane), respectively. The production of considerable amounts of light -alkanes is a disadvantage of this reaction route. Furthermore, the yield of the desired alkylate is reduced relative to isobutane and alkene consumption (8). For example, propene alkylation with HF can give more than 15 vol% yield of propane (21). Aluminum chloride-ether complexes also catalyze self-alkylation. However, when acidity is moderated with metal chlorides, the self-alkylation activity is drastically reduced. Intuitively, the formation of isobutylene via proton transfer from an isobutyl cation should be more pronounced at a weaker acidity, but the opposite has been found (92). Other properties besides acidity may contribute to the self-alkylation activity. Earlier publications concerned with zeolites claimed this mechanism to be a source of hydrogen for saturating cracking products or dimerization products (69,93). However, as shown in reaction (10), only the feed alkene will be saturated, and dehydrogenation does not take place. 

Aluminum hydride decomposes in air and water. Violent reactions occur with both. It forms a complex, aluminum diethyl etherate with diethyl ether. The product decomposes in water releasing heat. 

Aluminum trichloride (A1C13) dissolves in ether with the evolution of a large amount of heat. (In fact, this reaction can become rather violent if it gets too warm.) Show the structure of the resulting aluminum chloride etherate complex. 

Properties Amber clear liq. sol. in alcohols, glycol ethers, esters, ketones, aromatic hydrocarbons sp.gr. 1.10 vise. 100 cps 65% aluminum complex... 

The dimeric dicyclopentadienyl methyl yttrium complex reacts readily with methyl aluminum dichloride with loss of the methyl group and formation of a stable di- u-chloro-bridged dicyclopentadienyl yttrium dimethyl aluminum complex (Holton et al., 1979c), and dicyclopentadienyl yttrium chloride reacts with aluminum hydride in ether with formation of a white crystalline 2 1 1 complex, of which the X-ray structure was determined (Lobkovskii et al., 1982) ... 

Lithium aluminum hydride reacts violently with water, and therefore reductions with lithium aluminum hydride must be carried out in anhydrous solutions, usually in anhydrous ether. (Ethyl acetate is added cautiously after the reaction is over to decompose excess LiAIH4 then water is added to decompose the aluminum complex.)... 

TMS, TMS, TMS A1 Tris(trimethylsilyl)aluminum Tris(trimethylsilyl)aluminum-Ethyl Ether Complex 65343-66-0 75441-10-0 745... 

The highly electrophilic cationic bis(8-quinolinolato)aluminum complex 407 enabled Yamamoto and coworkers to perform Mukaiyama-Michael additions of silyl enol ethers to crotonylphosphonates 406. The procedure was not only applicable to enol silanes derived from aryl methyl and alkyl methyl ketones (a-unsubstituted silicon enolates) but also to several cycfic a-disubstituted silyl enol ethers, as illustrated for the derivatives of a-methyl tetralone and indanone 405 in Scheme 5.105. Despite the steric demand of that substitution pattern, the reaction occurred in relatively high chemical yield with varying diastereoselectivity and excellent enantiomeric excess of the major diastereomer. The phosphonate residue was replaced in the course of the workup procedure to give the methyl esters 408. The protocol was extended inter alia to the silyl enol ether of 2,6,6-tetramethylcyclohexanone. The relative and absolute configuration of the products 408 was not elucidated [200]. 

Scheme 5.105 Conjugate addition of silyl enol ethers 405 to crotonylphosphonates 406, mediated by aluminum complex 407.

Though their applications as polymerization catalysts fall outside the remit of the present chapter, a general discussion of the advent of cationic aluminum complexes supported by various ligands is warranted [46]. Over the last two decades cationic aluminum complexes have been very intensively investigated and promise enhanced substrate coordination and activation by virtue of their increased electrophilicity. Early systematic works focused on the use of crown ethers and the synthesis of complexes [Cl2Al(benzo-15-crown-5)][Me2AlCl2] and... 

To avoid the intrinsic instability of cyanohydrins and their silyl ether, Saa and coworkers reported catalytic asymmetric cyanophosphonylation reaction of aldehydes with commercially available diethyl cyanophosphonate [58]. In these works, Lewis acid-Lewis base bifunctional catalyst (65) prepared by mixing BI-NOLAM ligand with amino arms as Lewis base and Et2AlCl was found to work nicely (Scheme 6.46). Since a strong positive nonlinear effect was observed in this reaction, actual catalyst is in equilibrium with some oligomeric species of the aluminum complexes. Bifunctional catalyst (65) could also catalyze cyanosilylation of... 

Asymmetric Catalytic [2+2] Cycloaddition Reaction Using a Chiral Aluminum Complex In 2007, Canales and Corey provided the first enantioselective [2+2] cycloadditions of sUyl enol ethers with a, 3-unsaturated esters by catalytic amounts of aluminum bromide complex [21]. Aluminum catalyst 18 is conveniently generated in situ by the addition of a commercially available solution of aluminum bromide in CH2Br2 to a solution of the known oxazaborohdine component [22,23]. The results of enantioselective [2+2] cycloaddition reaction catalyzed by aluminum complex are summarized in Table 4.6. 

Claisen and related sigmatropic rearrangements have traditionally represented difficult scenarios for enantioselective catalysis. Consequently, Yamamoto s 1990 report that allyl vinyl ethers 97 undergo enantioselective rearrangement in the presence of chiral aluminum complexes 96 constituted a breakthrough in the discipline (Equation 8) [76]. In the presence of 1-2 equiv of the bulky aluminum complex 96, the rearranged products were isolated with impressive yield and enantioselectivity (cf. 98 99% yield, 88% ee). 

Boron tritiuoride etherate— -hexanol complexes have successfully been used to polymerize P-pinene, as well as dipentene, to yield resins with softening points >70° C (82). Limonene or dipentene sulfate has been polymerized with aluminum chloride in a mixed toluene/high boiling aUphatic naphtha to give high yields of light colored resins (96). For the polymerization of dipentene or limonene, 4—8 wt % of AlCl has been used. Polymerization of P-pinene typically requires lower levels of catalyst relative to limonene or dipentene. 

Aluminum chloride dissolves readily in chlorinated solvents such as chloroform, methylene chloride, and carbon tetrachloride. In polar aprotic solvents, such as acetonitrile, ethyl ether, anisole, nitromethane, and nitrobenzene, it dissolves forming a complex with the solvent. The catalytic activity of aluminum chloride is moderated by these complexes. Anhydrous aluminum chloride reacts vigorously with most protic solvents, such as water and alcohols. The ability to catalyze alkylation reactions is lost by complexing aluminum chloride with these protic solvents. However, small amounts of these "procatalysts" can promote the formation of catalyticaHy active aluminum chloride complexes. 

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