Organoalanes

Among the hydrometallations reported to date, hydroboration and hydrosilylation have been the most widely investigated while hydroalumination has received less attention. The resulting organoalanes from hydroalumination are often more reactive than the organoboranes or organosilanes. While the first metal-catalyzed hydroalumination... 

Scheme 1.26. Acylation of organoalanes generated in situ by Zr-to-AI transmetallation...

Cross-coupling of organoalanes with ally lie acetals or ortho esters (cf., 10, 388).6 The Pd(0)-catalyzed coupling of alkenylalanes with 1 proceeds with exclusive attack at the y-position to provide alkenyl ethers. 

J. Schachtner and H.-D. Stachel, Organoalane-mediated isomerization of ascorbic and isoascorbic acid derivatives, Tetrahedron Asymmetry., 7 (1996) 3263-3276. 

Production of polyethylene and polypropylene by the Ziegler-Natta catalysts, prepared from Ti chlorides and organoalanes. 

Negishi and co-workers developed this carbometalation reaction of alkynes with organoalane-zirconocene derivatives, and it has since turned into an often used route to stereo- and regiodefined... 

I). Actually, the highest regioselectivity is observed with organoalane derivatives, possibly because aluminum coordinates with both oxygens in the substrate. This reaction was useful in syntheses of prostaglandin analogs. 

There is no reaction between MejAlCl and Cl2Zr(Cp->f )2, either - . This, however, cannot be explained by the relative acidities of Cl and Me. Organoalanes normally exist as double-bridged dimers, and halogens are better bridging ligands than Me. This donor property of Cl must be responsible for the diminished reactivity of Me2AlCl. 

This reaction of an epoxide with an organoalane was used in one step of a synthesis of ( )-7-oxaprostagIandin F, (7). Thus reaction of the epoxide (4) with the organoalane (5) gave (6) in rcspeciable yield. This was transformed in several steps into (7). 

Keywords Nickel catalysts, BINAP, Hydrometalation, Reduction, Cyclohexenols, Cyclohepten-ols, DIBALH, Carbon-metal bond, Organoalane... 

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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