Lithium tetraethylaluminate

With the purpose of employing a more soluble form of complexed lithium hydride in such a process, Ziegler and Gellert heated ethylene in ether under pressure at 120-140 °C with LAH, which had been prepared for the first time by Schlesinger and coworkers. To Ziegler s gratification LAH was smoothly converted into lithium tetraethylaluminate (10), which could be isolated in high yield as a crystalline adduct. As proof of structure, the same adduct was also synthesized by the admixture of the lithium and aluminum ethyl derivatives in a 1 1 ratio (Scheme 2). This study represents the first authenticated instance of hydroalumination. 

Lithium tetraethylaluminate (10.0 g, 67 mmol) in ether (50 ml) was treated with freshly sublimed bismuth chloride (15.0 g, 46 mmol) in the same solvent (50 ml). A large quantity of gray precipitate was formed. After refluxing for 1 h and subsequent hydrolysis, triethylbismuthine was extracted with ether. The bulk of the solvent was removed by fractional distillation through an efficient column and the residue was further fractionated under reduced pressure to give pure bismuthine (12.0 g, 85%), b.p. 90°C/48 mmHg [62AJC710]. 

We also studied the feasibility of using triethylborane, lithium tetraethylborate, diethylzinc, and lithium triethylzincate vide infra) and found that the borate and zincate also underwent the substitution reaction with high degree of inversion but with a formation of by-products as summarized in Table 4. Thus, lithium tetraethylaluminate is concluded to be the best ethylation reagent for the ethylation of hemiacetal tosylate CF3CH(OCH2Ph)OTs. 

Sodium tetraethylaluminate and lithium tetrabutylaluminate alkylate oxiranes stereo- and regioselectively. In the case of aliphatic oxiranes, the reaction takes place on the less-substituted carbon atom, while in the case of a phenyl substituent, it occurs at the benzylic position, always with inversion. In the presence of a catalytic quantity of nickel salt, the reaction is accelerated considerably. 

Sodium tetraethylaluminate and lithium tetra-n-butylaluminate, when used in non-co-ordinating hydrocarbon solvents, have been shown to be good alkylating agents for epoxides [equation (2)]. Attack is at the least substituted carbon... 

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