New Preparative Techniques and Procedures

Hydrides and Olefins 1. Lithium and Aluminum Hydrides 

The addition of metal and metalloid hydrides to carbon-carbon double bonds is not a new reaction, having been observed from time to time with silanes of the type R3SiH under free-radical conditions (4%, 85) and with boron hydrides (68). The versatility of such hydride-olefin interactions, nevertheless, first became evident with the recent researches of Ziegler with lithium and aluminum alkyls (139). The observation that attempted distillation of ethyllithium led to decomposition into lithium hydride, ethylene, and higher olefins prompted the following formulation of the reaction course (see 18)  

Because of the widespread utility of aluminum alkyls preparative methods have been developed which place these compounds among the potentially cheapest organometallic reagents. Since aluminum hydride adds to ethylene at moderate temperatures, 

Two limitations on the synthesis are, first, that the olefins utilized must have a terminal double bond (a-olefins) and, second, that the use of the 

Other interesting aspects of this new synthesis of aluminum alkyls stem from the fact that hydride additions to olefins are reversible. In the first place this means that favorably constituted aluminum alkyls should lose olefin readily upon being heated. Such branched-chain alkyls as triisobutyl-aluminum will evolve isobutylene upon heating at 150-180°  

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