Organogallium reagents

Organogallium reagents, RsGa, have been added enantioselectively to aldehydes, using TiCl4 as a Lewis acid catalyst, with a chiral salan ligand.258... 

Organogallium compounds are good nucleophiles for performing addition reactions to carbonyl functionalities. Alkylation, allylation, aldol condensation, and the Reformatsky reaction proceed readily with organogallium reagents. 

Hydroalumination of alkenes by LAH, catalyzed by Ti and Zr chloride complexes, was demonstrated by two Japanese groups (equation 58).Subsequently this reaction has been extended to other sources of A1—H and other catalysts. Further information on catalyzed hydroalumination may be found in Chapter 3.11 of this volume as well as in an earlier review.Hydrogallation by NaGaH4/[Cp2MCl2] (M = Ti, Zr) has been briefly examined and appears quite similar,little if anything is known about the synthetic utility of organogallium reagents. 

Huang reported that organogallium reagents can be generated by treating allyl or... 

This method bears some similarities to the Grignard Reagent method in that product formation is often accomplished with solvent association. In particular, this method has been useful in preparing sterically demanding organogallium compounds, (Aryl)3Ga (vide infra). 

The utilization of organogallium as an alkylation reagent for asymmetric alkylation of aldehydes has been realized by using titanium complex as a chiral Lewis acid catalyst. The titanium catalyst was obtained by the reaction of TiCU with a salan [N,N-bis(o-hydroxybenzyl)-l,2-diaminoethane] type ligand. Moderate to good chemical yields were obtained with up to 84% ee [53] (Scheme 14.8). 

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