Organoaluminum compounds conversion

Early attempts by Asinger to enlarge the scope of hydroalumination by the use of transition metal catalysts included the conversion of mixtures of isomeric linear alkenes into linear alcohols by hydroalumination with BU3AI or BU2AIH at temperatures as high as 110°C and subsequent oxidation of the formed organoaluminum compounds [12]. Simple transition metal salts were used as catalysts, including tita-nium(IV) and zirconium(IV) chlorides and oxochlorides. The role of the transition metal in these reactions is likely limited to the isomerization of internal alkenes to terminal ones since no catalyst is required for the hydroalumination of a terminal alkene under these reaction conditions. 

The four orbitals of the M shell of the aluminum atom are occupied by only three electrons (3s2,3p), which give rise to the coordinatively unsaturated character of the element (sp2 hybrid). For organoaluminum compounds (Lewis acids) the conversion to the stable rare gas configuration can... 

Cyclization of terpene derivatives. Japanese chemists have devised a method for biomimetic conversion of acyclic terpene allylic phosphates into cyclic compounds based on organoaluminum compounds. Of several reagents tested of this type, tetraisobutyidialuminoxane (1) proved to be most selective. Two of the cyclizations realized with 1 are formulated in equations (I) and,(II). 

The formation of three-dimensional networks of the form shown in Structure 10.4 is hindered stericaUy and is accompanied by side reactions, e.g., diol cyclizadon, as in reactions of 1,4-butanediol with organoaluminum compounds [18], or dehydrocy-clization, as in reactions of 1,4-butanediol and other diols with Cp MCl [19]. Such processes prevent conversion from reaching 100%, as also evidenced by the presence of residual chlorine in the polymers. 

The Reformatskii reaction can be carried out conveniently with magnesium. If tert-huiy esters are used, the products can subsequently be transformed into satd. acids in a single operation Another easy method for the conversion of aldehydes to nitriles is their treatment with lead tetraacetate and ammonia in benzene Hydrocyanations can be efficiently performed with the help of organoaluminum compounds In this manner, steroidal cyanohydrins can be obtained from the respective epoxides by diaxial fission under mild conditions in high yield A number of addition reactions of nitrile oxides have been reported contrary to earlier reports, ar. nitrile oxides easily add hydrogen halides. 

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