Al-alkyls

Mixed-Metal Systems. Mixed-metal systems, where a zirconium alkyl is formed and the alkyl group transferred to another metal, are a new apphcation of the hydrozirconation reaction. These systems offer the advantages of the easy formation of the Zr—alkyl as well as the versatiUty of alkyl—metal reagents. For example, Cp2ZrRCl (R = alkyl or alkenyl) reacts with AICI3 to give an Al—alkyl species which may then be acylated with... 

Fuming sulfuric acid containing 10-60% sulfur trioxide hydrolyzes perfluoro-Af-alkylcyelic amines to perfluoro-Al-alkyl lactams. Mercuric sulfate acts as a Catalyst [JO, 31] (equation 33). The lactams ate highly reactive and can be used to prepare polymenc films and surfactants... 

Butadiene-Styrene Copolymers from Ba-Mg-Al Catalyst Systems. Figure 13 shows the relationship between copolymer composition and extent of conversion for copolymers of butadiene and styrene (25 wt.7. styrene) prepared in cyclohexane with Ba-Mg-Al and with n-BuLi alone. Copolymerization of butadiene and styrene with barium salts and Mg alkyl-Al alkyl exhibited a larger initial incorporation of styrene than the n-BuLi catalyzed copolymerization. A major portion of styrene placements in these experimental SBR s are more random however, a certain fraction of the styrene sequences are present in small block runs. 

A1 + CHBr3 Al-alkyl bromide + AlBr3 CHBr3 MBr3. polymer - AHr... 

Several organo-titanium compounds with the oxidation states IV, III, II, 0,-1 have been prepared. A starting point was the discovery by Ziegler et al. (1955), Ziegler (1963) and Natta et al. (1955) and Natta (1963) of the catalytic properties of TiClj-Al-alkyl mixtures in hydrocarbons in reactions such as the ethylene and propylene polymerization. 

Ligands are not always innocent spectator groups. Cationic j -diiminate alkyl complexes of aluminium, rather than undergoing insertion in the Al-alkyl bond, show attack of the unsaturated substrate (ethene or acetylene) at the ligand (Scheme 1). Surprisingly, the C-C coupling reaction observed with ethene is reversible [42]. 

The chemistry used to prepare the antischistosomal hydroxyquinolines provided the initial entry to this series. Thus, addition-elimination of aminopicoline (38-1) to EMME (38-2) gives the corresponding enamino ester (38-3). Thermal cyclization of that intermediate leads to the hydroxyquinoline (38-4). Reaction of the ambident anion from that compound leads to alkylation via the keto tautomer and thus the formation of the Al-alkylated derivative (38-5). Saponification of the ester then gives nalidixic acid (38-6) [44]. It has incidentally been shown that the presence of the strong Michael acceptor function in this series plays a little role in the mechanism of action in these compounds. 

Reaction (21) occurs with cyclohexene and both cis- and trans-2-butene, without isomerization of the alkenes,139 while the reduction of Ni(acac)2 with Al(alkyl)3 in the presence of PCy3 and 2-butene (cis and trans) affords the complex bis(tricyclohexylphosphine)(l-butene)nickel(0)>... 

Illustrative examples of the acylation of support-bound amines with carbodiimides as coupling agents are listed in Table 13.3. Difficulties are usually encountered in the acylation of a-alkylamino acid derivatives (which are significantly less nucleophilic than simple secondary amines Entries 3 and 4) and Al-alkyl (Entries 5 and 6) or iV-aryl anilines. Acylations with haloacetic or related acids containing a leaving group prone to nucleophilic displacement should not be performed with the aid of HOBt and bases because O-alkylation of HOBt by the product occurs readily. 

Guidelines a. Air ACGIH TLV TWA Aluminum metal dust pyro powders, as Al welding fumes, as Al soluble salts, as Al alkyls (not otherwise classified) Aluminum oxide 10 mg/m3 5 mg/m3 5 mg/m3 2 mg/m3 2 mg/m3 10 mg/m3 ACGIH 1996... 

Totten LA, Jans U, Roberts AL. Alkyl bormides as mechanistic probes of reductive dehalogenation reactions of vicinal dibromide stereoisomers with zerovalent metals. Environ Sci Technol 2001 35 2804-2811. 

The solubility of rare earth hydrides in organic solvents is increased by appropriate additives, too. For this purpose the hydrides are reacted with electron-donor ligands such as alkyl benzoates, alkyl propionates, alkyl tolu-ates, dialkylethers, cyclic ethers, alkylated amines, N,N -dimclhylacelamide, AT-methyl-2-pyrrolidone, trialkyl and triaryl phosphines, trialkyl phosphates and triaryl phosphates, trialkyl phosphates, hexamethylphosphoric triamide, dimethyl sulfoxide, etc. Prior to use as a polymerization catalyst the prereacted mixture of the rare earth hydride plus the additive is prereacted with Al-alkyl-based Lewis acids in the temperature range of 60-100 °C for 10 min to 24 h [351,352]. 

Already in his pioneering study Throckmorton investigated the impact of Ai/ ce-ratios for different Al-alkyls on dilute solution viscosities (DSV) [34], Throckmorton found that for the two ternary catalyst systems Ce octanoate/AlR3/DEAC and Ce octanoate/AlR3/EtAlCl2 dilute solution vis-... 

To our knowledge there is no study available on the formation and the nature of the active species present in Nd-phosphate-based catalyst systems. Such a study should be designed to elucidate the question why extraordinary small amounts of Al alkyls ( ai/ n < 4) are sufficient for catalyst activation. 

In ternary Nd Ziegler/Natta catalyst systems of the type Nd compound/cocatal-yst/halide donor Al alkyl cocatalysts yield high czs-l,4-BR whereas Mg alkyl cocatalysts yield fra s-l,4-poly(butadiene). To date, it is not clear why the use of these two classes of co catalysts leads to completely different polymer microstructures. 

The reduction of the molar ratio of Al/MNd constitutes another key to the reduction of overall catalyst costs. Especially in NdV-based catalyst systems a considerable portion of the expensive Al- alkyl is consumed in the activation of Nd-carboxylates and other reactions prior to the formation of the active Nd-species (Sect. 4.2) [178]. The formation of the active Nd-species from Nd-phosphate precursors requires a comparably low amount of Al-alkyls [272] as Nd-phosphate-based catalyst systems are active at very low molar ratios of Al/ Nd < 5 (Sects. 2.1.1.4 and 2.1.4) [268,269,272],... 

Anstelle von Wasser lassen sich auch Carbonsauren als Alkyl-Akzeptoren zur Spaltung von Phosphonsaure-dialkylestern verwenden, wobei als saurer Katalysator Schwefelsaure, Phosphorsaure oder Sulfonsauren eingesetzt werden65,66 ... 

The addition of aluminum hydride and alkyls to non-activated C-C multiple bonds (C=C or C=C) is referred to as hydroaluminaton and carboalumination, respectively. The reactions involve metathesis of each C-C multiple bond with Al-H or Al-C bonds, giving an Al-C =C-H (or Al-C-C-H) or A/-C=C-C (or A/-C-C-6) structure, respectively. These methods are of broad utility in the construction of Al-C linkages, including Al-alkenyl and Al-alkyl bonds, which can be further converted into C-C bonds (Equations (42)-(45)).192-196 Therefore, a great contribution has been made in synthetic applications, in addition to the mechanistic studies, of hydroalumination and carboalumina-tion since 1993.197-199... 

Other workers also report studies on alkylation of aromatics over silica-alumina (63). Ivanov el al. alkylated coal-tar aromatics with olefins in the presence of aluminum chloride-hydrogen chloride and obtained a product suitable for use as a lubricating oil (143). Topchiev and Paushkin have reported high yields in the alkylation of isopentene with propylene in the presence of a catalyst containing phosphoric acid and boron trifluoride (395). 

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