Alkyl aluminum dichlorides

Controlled alkylation of phosphorus oxychloride may also be accomplished using a modification of this approach. Reaction of alkyl-aluminum dichloride with phosphorus oxychloride generates the aluminum chloride complex of the alkylphosphonodichlori-date,54 which may be isolated as the simple compound or directly used in reaction to generate other derivatives of the alkylphospho-nic acid. 

The alkyrlaluminums were obtained from Texas Alkyls Inc. and purified by vacuum distillation in nitrogen atmosphere. B.P. °C/mm Hg MCaAl 60768.5 EtjAl 977100 Et AlCl 125-126750mm MejAlCl 847200. Prior to distillation the dialkylaluminum chlorides were stirred over dry sodium chloride at 80° C for 2 hrs. to remove alkyl-aluminum dichlorides. The distilled dialkylaluminum chlorides were stored over sodium chloride to prevent the accumulation of the dihalide. 

Catalyst - aluminum trichloride, alkyl aluminum dichloride, boron trifluoride, tin tetrachloride, and titanium tetrachloride ... 

Using a solution process, the choice of catalyst system is determined, among other things, by the nature of the third monomer and factors such as the width of the mol wt distribution to be realised in the product. A number of articles review the induence of catalyst systems on the stmctural features of the products obtained (3,5—7). The catalyst comprises two main components first, a transition-metal haHde, such as TiCl, VCl, VOCl, etc, of which VOCl is the most widely used second, a metal alkyl component such as (C2H )2A1C1 diethylalurninum chloride, or monoethyl aluminum dichloride, (C2H )AlCl2, or most commonly a mixture of the two, ie, ethyl aluminum sesquichloride, [(C2H )2Al2Cl2]. 

Breslow and Newburg (125) studied the reaction of biscyclopenta-dienyltitanium dichloride and alkyl aluminums. They postulated that the reduction of the metal occured through an intermediate dialkylation which rapidly eliminated olefin and alkane. Bawn (126) has found that the reaction of cobalt acetylaeetonate and triethylaluminum gives disproportionation to ethane and ethylene at the beginning and dimerization of the ethyl group to butane at the end. 

Soluble catalysts, such as diethyl aluminum chloride and ethyl aluminum dichloride, also affect the stereoregularity of the polymer chains. The tendency for the formation of stereoregular polymers is decreased as the size of the alkyl group is increased. Typical structures of these polymers are shown below ... 

An alternate route to formation of alkyl monolayers is via Lewis acid catalyzed reactions of alkenes with the hydrogen terminated surface. In this approach, a catalyst such as ethyl aluminum dichloride is used to mediate the hydrosilylation reaction of an alkene (or alkyne), resulting in the same type of product as in the case of the photochemical or thermal reactions. This type of reaction is well known based on molecular organosilane chemistry and has also been used successfully to alkylate porous silicon [31]. Although this route has been shown to work on H/Si(lll), the resulting monolayers are found to have lower coverages than those achieved using the photochemical or thermal approach [29], Another concern with this approach is the possibility of trace metal residues from the catalyst that could adversely affect the electronic properties of these surfaces (even when present at levels below the detection limit of most common surface analysis techniques). 

The ethyl aluminum dichloride-catalyzed Michael alkylations of some indoles with N-(diphcnylmethylcnc)-a,()-didehydroamino acid esters allowed successful short synthesis of the tryptophan derivative and the 1,1-diphenyl-p-carboline derivatives, as well as compounds 253 and 252 (Scheme 55) [ 178]. 

Ethyl aluminum dichloride mediates a formal [5 + 2] cycloaddition of complex (164) and (166) with enol silyl ethers to produce the highly strained seven-membered rings (165) and (167) respectively (Schemes 239 -240). Excellent stereoselectivity is observed in both cases. A related double alkylation affords complexed seven-membered rings via a formal [4 - - 3] cycloaddition. Incorporation of fluorine is observed using boron trifluoride etherate (Scheme 241). 

Alkyl halides are widely used as cocatalysts in combination with aluminum alkyl halides or aluminum halide Lewis acids. Tlie reaction scheme in Fig. 9-2 illustrates the complicated equilibria which may affect the initiation process. Each carbenium ion can initiate polymerization or remove an ethyl group from the counterion to produce a saturated hydrocarbon, REt, and a new more acidic Lewis acid. The propagating macrocarbenium ions can also terminate by the same process to produce ethyl-capped polymers and new Lewis acids. Thus, even though the initiator is ostensibly dielhylaluminum chloride there may be major contributions to the polymerization from ethyl aluminum dichloride or aluminum chloride. 

A ternary system that consists of a zirconocene dichloride, a trialkyl aluminum, and Ph3C+B(C6F5)4 has been developed by Chien et al. for ethylene and propylene polymerizations with superb activity. The use of excess of R3AI serves both to alkylate the dichloride precursor as well as to scavenge O2. H2O. and other protic impurities in the system. The entire activation process can be perceived as the initial in-situ alkylation of the zirconocene dichloride by the alkylaluminum, followed by subsequent oxidative cleavage of a Zr—R bond by Ph3C+ (eq 45). This... 

The general consensus on the mechanistic details of transition metal-catalyzed polyethylene formation is that the active site comprises a metal with an alkyl group as active chain end and a free coordination site, with the metal incorporated in a ligand or in a salt crystal [32]. Ethylene is inserted in a syn fashion into the metal-carbon bond. Iron bis(iminoaryl)pyridyl dichloride (BI P FeCl2, where R denotes the ortho substituents on the aryl entity Fig. 1) in combination with MAO or (tri)alkyl aluminum compounds (AIR3) yields active ethylene polymerization systems [23]. Both the free coordination site and the alkyl group of the iron center thus originate from the interaction with the aluminum compounds. 

With monoalkyl-aluminum dichloride, on the other hand, no reduction occurs at room temperature and below. The catalyst remains in solution and in the presence of ethylene oligomer is formed. Evidently, the relatively low electrmi density at the Ti(IV) center (high electron affinity, high acidity, or however one wishes to express the situation) favors the molecular weight-reducing -hydrogen abstraction, Eq.(2). Not only the valency of the titanium ion itself, but also the presence of the acceptor ligands Cl at the titanium center and at the aluminum alkyl contribute to the acidity of the catalyst center. 

The other commercially important routes to alkyltin chloride intermediates utilize an indirect method having a tetraalkjitin intermediate. Tetraalkyltins are made by transmetaHation of stannic chloride with a metal alkyl where the metal is typicaHy magnesium or aluminum. Subsequent redistribution reactions with additional stannic chloride yield the desired mixture of monoalkyl tin trichloride and dialkyltin dichloride. Both / -butjitin and / -octjitin intermediates are manufactured by one of these schemes. 

Methylphenol is converted to 6-/ f2 -butyl-2-methylphenol [2219-82-1] by alkylation with isobutylene under aluminum catalysis. A number of phenoHc anti-oxidants used to stabilize mbber and plastics against thermal oxidative degradation are based on this compound. The condensation of 6-/ f2 -butyl-2-methylphenol with formaldehyde yields 4,4 -methylenebis(2-methyl-6-/ f2 butylphenol) [96-65-17, reaction with sulfur dichloride yields 4,4 -thiobis(2-methyl-6-/ f2 butylphenol) [96-66-2] and reaction with methyl acrylate under base catalysis yields the corresponding hydrocinnamate. Transesterification of the hydrocinnamate with triethylene glycol yields triethylene glycol-bis[3-(3-/ f2 -butyl-5-methyl-4-hydroxyphenyl)propionate] [36443-68-2] (39). 2-Methylphenol is also a component of cresyHc acids, blends of phenol, cresols, and xylenols. CresyHc acids are used as solvents in a number of coating appHcations (see Table 3). 

Addition. Addition reactions of ethylene have considerable importance and lead to the production of ethylene dichloride, ethylene dibromide, and ethyl chloride by halogenation—hydrohalogenation ethylbenzene, ethyltoluene, and aluminum alkyls by alkylation a-olefms by oligomerization ethanol by hydration and propionaldehyde by hydroformylation. 

Activity on cell proliferation is maintained when a major part of the side chain is replaced by an amide linkage. The tetralin-based compound tamibarotene (15-7) has been tested as an agent for treating leukemias. Reaction of the diol (15-1) with hydrogen chloride affords the corresponding dichloro derivative (15-2). Aluminum chloride-mediated Friedel-Crafts alkylation of acetanilide with the dichloride affords the methylated tetralin (15-3). Basic hydrolysis then leads to the primary... 

Long (81) showed that the complex from biscyclopentadienyltitanium dichloride and methylaluminum chloride or a simply derived product from it, was an active ethylene polymerization catalyst. There have been a number of attempts to determine the exact nature of initiation in polyethylene. However, by any techniques available until now, it has not been possible to determine the actual ionic nature of the active catalyst which polymerizes ethylene. Karapinka and Carrick (82) studied the polymerization of ethylene with biscyclopentadienyltitanium dichloride and various alkylaluminum compounds. They found that the alkyl group exchanged so readily between the aluminum and titanium, that the location of the initiating site could not be determined. All that could be concluded was that an ethyl group initiated the polymerization more easily than the phenyl. 

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