Metal-Catalyzed Hydroalumination Reactions

In contrast to the related organoboranes, which are mostly used in the addition to non-polar carbon-carbon multiple bonds, aluminum hydrides have found their widest use in organic synthesis in the addition reaction to polar carbon-carbon and carbon-heteroatom multiple bonds including carbonyl, nitrile and imino groups as well as their a,(J-unsaturated analogs. Although these reduction reactions are also sometimes referred as hydroalumination reactions in the Hterature, they are outside the scope of this review. 

Because of the polarity of the carbon-aluminum bond, organoaluminum compounds are valuable intermediates in organic synthesis, which exhibit higher reac- 

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In order to get reliable information about the yield of organoaluminum compounds formed in a transition metal-catalyzed hydroalumination reaction it is essential to derivatize the organometallic products by quenching the reaction mixture with electrophiles like D2O, O2 or halogens. It is often observed that hydrogenation... 

I 2 Metal-Catalyzed Hydroalumination Reactions 1. fPr2N)2AIH... 

This chapter has been organized into three sections. The first section deals with transition metal-catalyzed hydroboration in organic synthesis and this is divided into three subsections - mechanism, chemoselectivity, and stereoselectivity. The second section deals with the application of transition metal-catalyzed hydroalumination reactions in organic synthesis, and this is also divided into three subsections - mechanism, chemoselectivity, and stereoselectivity. The third section examines the application of both hydroborations and hydroaluminations in total synthesis. 

In 1954, Ziegler and coworkers [11,12] reported that traces of nickel salts dramatically alter the course of the growth reaction of ethylene with trialkylalanes, the Aufbau process. Instead of the low molecular weight polyethylene which was expected, the only product was butene. This observation culminated in Ziegler s discovery of transition metals that were highly effective in polymerizing ethylene, an accomplishment for which he later shared the Nobel Prize. It also opened the door to transition metal catalyzed hydroalumination reactions. In 1968, Eisch and Foxton showed that addition of nickel(II) salts increased the rate of the hydroalumination of alkynes by approximately 100-fold [13]. The active catalyst was believed to be a nickel(O) species. 

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