Reactions of alkenyl- and alkynylaluminium compounds
Reactions of alkenylalanes
### Reactions of alkenylalanes

Alkenyl\- and alkynylaluminates are most commonly generated through the addition of *n*\-butyllithium to the alkenylalane. The alkenyl and alkynyl groups, which are better able to stabilize negative charge, are transferred in preference to the alkyl group. When these intermediates react with alkyl halides, functionalized olefins are produced.Zweifel, G.; Lynd, R. A. *Synthesis* **1976**, 816\.
***(8\)***[center](/wiki/File:AlaneScope4.png "AlaneScope4.png")
Treatment of alkenylaluminates with halogen electrophiles such as *N*\-bromosuccinimide (NBS) and iodine leads to the formation of halogenated olefins.Palei, B. A.; Gavrilenko, V. V.; Zakharkin, L. I. *Izv. Akad. Nauk SSSR, Ser. Khim.* **1969**, 2760 \[C.A., 72, 79143s (1970\)]. These products are useful for cross\-coupling reactions.
***(9\)***[center](/wiki/File:AlaneScope5.png "AlaneScope5.png")
Zirconium\-catalyzed carboalumination of alkynes by trimethylalane is a convenient method for accessing substituted alkenylalanes stereoselectively.Yoshida, T.; Negishi, E.\-i. *J. Am. Chem. Soc.* **1981**, *103*, 4985\. Upon exposure to aldehydes and ketones, alkenylalanes form secondary or tertiary allylic alcohols. Formaldehyde is a useful reagent in this context for the introduction of a hydroxymethyl unit.Negishi, E.\-i.; King, A. O.; Klima, W.; Patterson, W.; Silveira, Jr., A. *J. Org. Chem.* **1980**, *45*, 2526\.
***(10\)***[center](/wiki/File:AlaneScope6.png "AlaneScope6.png")
Alkynylalanes are primarily used in place of the corresponding alkali metal acetylides when the latter reagents are ineffective. The coupling of an acetylide and tertiary alkyl halide is an example of a reaction that cannot be accomplished with alkali metal acetylides, which displace halides in an SN2 fashion. The corresponding alkynylalanes are able to couple to tertiary halides via an SN1\-like mechanism.
***(11\)***[center](/wiki/File:AlaneScope7.png "AlaneScope7.png")
Alkynyl\- and alkenylalanes add in a conjugate fashion to enones in the *s*\-*cis* conformation without nucleophilic activation. Enones locked in an *s*\-*trans* conformation, such as cyclohexenone, are unreactive. The coordination of oxygen to aluminium is believed to be necessary for this reaction.Hooz, J.; Layton, R. B. *Can. J. Chem.* **1973**, *51*, 2098\.
***(12\)***[center](/wiki/File:AlaneScope8.png "AlaneScope8.png")
When alkynes and dialkylalanes are combined in a 2:1 ratio, 1,3\-dienes result. The aluminium\-carbon bond of the initially formed alkenylalane adds across a second molecule of alkyne, forming a conjugated dienylalane. [Protonolysis](/wiki/Protonolysis "Protonolysis") provides the metal\-free diene product.Zweifel, G.; Snow, J. T.; Whitney, C. C. *J. Am. Chem. Soc.* **1968**, *90*, 7139\.
***(13\)***[center](/wiki/File:AlaneScope9.png "AlaneScope9.png")
Alkenyl\- and alkynylalanes undergo transmetalation to a variety of metals, including boron,Negishi, E.\-i.; Boardman, L. D. *Tetrahedron Lett.* **1982**, 3327\. zirconium, and mercury.Negishi, E.\-i.; Jadhav, K. P.; Daotien, N. *Tetrahedron Lett.* **1982**, 2085\.
***(14\)***[center](/wiki/File:AlaneScope10.png "AlaneScope10.png")


How do the properties of alkenylalanes make them useful for certain reactions?