Organometallic reagents lithium aluminum hydride

Similar to the case for its reaction with lithium aluminum hydride, an ester reacts with a Grignard or organolithium reagent to produce a ketone as the initial product. But because the ketone also reacts with the organometallic reagent, an alcohol is the final product. The mechanism for this reaction is shown in Figure 19.10. Note the similarities between this mechanism and that shown in Figure 19.7 for the reduction of an ester with lithium aluminum hydride. 

Organometallic reagents that are more sterically demanding than sodium borohydride or lithium aluminum hydride add to cyclohexanones with observed stereoselectivities reflecting a balance between steric approach control and developing torsional interactions in the transition state. Steric approach control will be very... 

Openings of oxiranes by organometallic reagents or hydride reagents such as lithium aluminum hydride are valuable synthetic tools for making alcohols. 

Drying for uses in conjunction with organometallic reagents, moisture exclusion is necessary. Removal of water is best achieved by refluxing over lithium aluminum hydride or calcium hydride for 2 h under nitrogen and distilling immediately prior to use. 

Hydroalumination is a less often used reaction but the resulting organoalanes are more reactive than either organosilanes or boranes and less reactive than the traditional organometallic reagents derived from lithium or magnesium. Various aluminum hydrides are commercially available or readily prepared by reduction of aliuninum halides [10]. 

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