Organoaluminum compounds preparation

Prepa.ra.tlon, There are several methods described in the Hterature using various cobalt catalysts to prepare syndiotactic polybutadiene (29—41). Many of these methods have been experimentally verified others, for example, soluble organoaluminum compounds with cobalt compounds, are difficult to reproduce (30). A cobalt compound coupled with triphenylphosphine aluminum alkyls water complex was reported byJapan Synthetic Rubber Co., Ltd. (fSR) to give a low melting point (T = 75-90° C), low crystallinity (20—30%) syndiotactic polybutadiene (32). This polymer is commercially available. 

Another method for the preparation of ketones is the reaction of imidazolides, ben-zimidazolides, or benzotriazolides with organoaluminum compounds [94]... 

Evidence has been collected over the years which strongly indicates that the active species in the oligomerization reactions are nickel-hydride and nickel-alkyl complexes. [This is not necessarily true for catalysts prepared from nickel(II) compounds and organoaluminum compounds having low Lewis acidity, e.g., (C2H5)2A10C2H5 (44).] The majority of the evidence is circumstantial and is discussed below. 

The sodium fluoride-water work-up offers an excellent method for large-scale preparations, and is generally applicable, for product isolation in the reaction of organoaluminum compounds. ... 

The Ziegler-Natta catalysts are prepared by the reduction of TiIV compounds, e.g., TiCl4 or esters of titanic acid, by organoaluminum compounds. A higher catalyst activity and thus an improved polymer color is achieved by the use of MgCh as support component. 

Finally, ring expansions of cyclic ketones are an important method for the preparation of carbocyclic systems. Diazoalkanes allow this reaction to occur and involve C—C bond formation. When combined with carefully chosen organoaluminum compounds, this process can be performed in a highly stereoselective fashion (equation 148)541. 

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