Trialkylaluminum complex

The existence of ketenes was established over a hundred years ago, and, in recent years, asymmetric synthesis based on [2 + 2] cycloadditions of ketenes with carbonyl compounds to form chiral p-lactones has been achieved with high yields and high stereoselectivities. In 1994, Miyano et al. reported the use of Ca-symmetric bis(sulfonamides) as ligands of trialkylaluminum complexes to promote the asymmetric [2 + 2] cycloaddition of ketenes with aldehydes. The corresponding oxetanones were obtained in good yields and enantioselectivities... 

Fluorine-Assisted Selective Alkylation to Fluorinated Epoxides and Carbonyl Compounds Implication of Pentacoordinate Trialkylaluminum Complexes ... 

In 1981 the first attempt for the asymmetric hydroalumination with a chiral alane reagent took place. The reaction of a chiral amine-trialkylaluminum complex, Al((-Bu)3-[(-)-DMMA] (172), with 1,1-dialkylethylenes (excess) catalyzed by Ni(Il)rMesal]2 (173) (2 mol%) without solvent, followed by exposure of the resulting adduct to the oxygen atmosphere gave the corresponding alcohols with low enantiopurity, for example, the reaction of 2-tm-butylpropene with 172 in the presence of 173 gave 144 with 27% ee (R) (Scheme 2.19) [98],... 

The impressive electrolytic systems due to Ziegler and co-workers are perhaps most widely known. These are based on research dating back to 1955. There are several patents on the electrolysis of sodium fluoride-trialkylaluminum complexes with a lead anode 334>, and the electrolysis of sodium or potassium tetraalkylaluminum 336>, as in the following examples ... 

Chart 10 Coordination modes in lanthanide trialkylaluminum complexes... 

The trialkylaluminum complexes 13.19,13.20 j.g largely used industrially for the dimerization and polymerization of olefins (see Chap. 14). They are prepared on a large scale from the metal and alkyl chloride or olefin and hydrogen. The laboratory syntheses are not common and involve the alkylation of AICI3 ... 

Trialkylaluminum and diethyl ether - triorganoaluminum complexes undergo addition to l-ni-trocycloalkenes in hexane at 0°C or 60°C, respectively to give adducts in good yield23. 

Nickel(O) reacts with the olefin to form a nickel(0)-olefin complex, which can also coordinate the alkyl aluminum compound via a multicenter bond between the nickel, the aluminum and the a carbon atom of the trialkylaluminum. In a concerted reaction the aluminum and the hydride are transferred to the olefin. In this mechanistic hypothesis the nickel thus mostly serves as a template to bring the olefin and the aluminum compound into close proximity. No free Al-H or Ni-H species is ever formed in the course of the reaction. The adduct of an amine-stabihzed dimethylaluminum hydride and (cyclododecatriene)nickel, whose structure was determined by X-ray crystallography, was considered to serve as a model for this type of mechanism since it shows the hydride bridging the aluminum and alkene-coordinated nickel center [31]. 

Polymer Preparation. A more recent modification in the molecular structure of styrene-butadiene copolymers has been obtained with the discovery of a new catalyst system (6). The catalyst consists of a barium t-alkoxide-hydroxide salt together with a complex of dialkylmagnesium and trialkylaluminum. 

Aluminum(III) complexes are amongst the most common Lewis acids. In particular, aluminum halide species (e.g., A1C13, AlBr3) are commercially available and are widely used for various reactions. Other types of Lewis acid such as aluminum alkoxides, alkylaluminum halides, and trialkylaluminum species are also used for many kinds of Lewis-acid-mediated reactions. 

AUyRc aluminum ate complexes. Carbanions of allylic sulfides and ethers generally react with electrophiles at both the a- and the y-position. If the carbanion is converted into an ate complex -with triethylaluminum, electrophiles react predominately at the a-position. After the reaction is completed the trialkylaluminum is destroyed with aqueous methanol. Boron ate complexes are not so generally useful for control of regioselectivity.1 Example ... 

Zirconocene dichlondc and related complexes catalyze the addition of trialkylaluminum compounds to tenninal acetylenes7 and olefins8 as well as the addition of ethyl, propyl, and butyl Grignard reagents to alkenes.9-12 These transformations occur with a high degree of regiosclectivity (cf. hydroboration), such that the metal atom always adds to the end position of a terminal multiple bond like that in 25. If addition is to a triple bond, M and R in the product are cis to each other... 

In systems completely free of chloride, complex formation between the titanium or zirconium compound and the trialkylaluminum was not detected by either NMR or UV spectroscopy 191), or by cryoscopy (189). Such systems were thus assumed to be inactive for polymerization. However, NMR-spectroscopic studies in the presence of ethylene revealed a weak but lasting insertion of ethylene, with formation of polyethylene. 

Alkylated rare-earth metal complexes with rare-earth metal centers surrounded exclusively by oxygen donor ligands were reported from facile ligand redistribution processes in 2,6-dimethylphenolate/trialkylaluminum mixtures. As shown in Scheme 29 for the yttrium derivatives Y(0ArMe,II)2[(//-OArMe>H)2AlR2](THF)2 (R= Me, Et), heterobimetallic 1 1-species were ac-... 

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