Organoaluminum compounds with halides

In order to prepare organoaluminum compounds with specific functional groups in the alkyl radical, reactions of aluminum halides with various metallic compounds are particularly important. Thus, vinyl magnesium halides and aluminum trichloride give unstable trivinylalane (see Section III,B,2) (17, 288) ... 

The alkylation of tin tetrachloride with organolithium compounds, Grignard reagents, or organoaluminum compounds remains the most common route to tetraalkyltins, and thence, by the Kocheshkov disproportionation, to the various organotin halides. 

Organoaluminum compounds couple very well with tertiary (to give products containing a quaternary carbon) and benzylic halides at -78°C.1301 This reaction can also be applied to allylic, secondary, and some primary halides, but several days standing at room temperature is required (see also 0-90). Products containing a quaternary carbon can also be... 

A highly convenient and versatile cyclopropanation method has been devised which involves treatment of olefins with different organoaluminum compounds and alkylidene iodide under mild conditions [93]. Although Miller found that cyclopropane formation by use of EtsAl-methylene iodide in cyclohexene proceeds in quite disappointing yields [94], Yamamoto and Maruoka reached the conclusion that the intermediate dialkyl(iodomethyl)aluminum species 97 is responsible for the cyclopropanation of olefins and that it readily decomposes in the absence of olefins or in the presence of excess trialkylaluminum. Hence the use of equimolar amounts of trialkyl-aluminum and methylene iodide in the presence of olefins is essential for the achievement of reproducible results in the cyclopropanation process. In addition, because di-alkylaluminum halide can also be used as a cyclopropanation agent, the use of half an equivalent of trialkylaluminum is not detrimental (Sch. 61). 

Finally, tetraorganoaluminates react with AI halides to give organoaluminum compounds ... 

The reaction between alkyl halides and aluminum metal is the basis of the oldest method for the synthesis of organoaluminum compounds. For example, propargylic bromides react with aluminum in ether giving organoaluminum compounds that on treatment with acetals yield solely a-allenic ethers (equation 1)." However, the reaction of simple alkyl halides with aluminum metal requires a long reaction time. 

Organoaluminum compounds are sufficiently Lewis acidic to interact with weak Lewis bases such as alkyl halides, although stable and thoroughly characterized examples are few. Instead, many trialkylaluminum compounds react violently with halogenated solvents. The adduct MeaSiF-AlEta, with weak F- -Al donation, has been characterized by NMR spectroscopy and this adduct is thermally stable to 30 °C. Structurally characterized examples of aryl halides forming dative bonds to aluminum have been reported for cationic organoaluminum complexes as will be discussed later. 

Highly syndiotactic polypropylene was prepared by Natta and co-Workers with homogeneous catalysts formed from VCU or from vanadium triacetylacetonate, aluminum dialkyl halide, and anisole at -48 to -7 8 °C. No isotactic fractions formed. This led to the development of many effective soluble catalysts. The catalyst components and the conditions for their preparation are quite important in maintaining control over syndiotactic placement. For the most effective soluble catalyst the ratio of AIR2X to the vanadium compound must be maintained between 3 and 10. The organic portion of the organoaluminum compound can be either methyl, ethyl, isobutyl, neopentyl, phenyl, or methylstyryl. " In addition to VCI4 and to vanadium triacetylacetonate, various other vanadates can be used, like [ VO(OR)/ l3 c], where x = 1,2, or 3 The exact nature of the vanadium... 

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