Multiple bonding aluminum

In contrast to the related organoboranes, which are mostly used in the addition to non-polar carbon-carbon multiple bonds, aluminum hydrides have found their widest use in organic synthesis in the addition reaction to polar carbon-carbon and carbon-heteroatom multiple bonds including carbonyl, nitrile and imino groups as well as their a,(J-unsaturated analogs. Although these reduction reactions are also sometimes referred as hydroalumination reactions in the Hterature, they are outside the scope of this review. 

Multiple Bonds Involving Aluminum and Gallium Atoms... 

Robinson, Gregory, H., Multiple Bonds Involving Aluminum and Gallium Atoms 47 283... 

Robinson, G. H. Multiple bonds involving aluminum and gallium atoms. Adv. Organomet. Chem. 2001, 47, 283-294. 

Aluminum hydrides add across carbon-carbon multiple bonds to form organo-alanes381-385 (hydroalanation or hydroalumination), which are usually further reacted with suitable electrophiles. The addition is thermal or may be catalyzed by metals, mainly titanium and zirconium compounds.386,387... 

The chemistry of alkyl and alkenyl azides has been well summarized in several recent reviews.233-237 The azides can be prepared via numerous methods, of which the addition of hydrazoic acid to C—C multiple bonds is one. With the exception of cyclopropenes,238 most alkenes are unreactive towards hydrazoic acid itself. However, the addition can be catalyzed by acids (phosphoric acid,239 sulfuric acid260 or trifluoroacetic acid261) or Lewis acids (aluminum trichloride, boron trifluoride or titanium tetrachloride).262... 

The addition of thiols to C—C multiple bonds may proceed via an electrophilic pathway involving ionic processes or a free radical chain pathway. The main emphasis in the literature has been on the free radical pathway, and little work exists on electrophilic processes.534-537 The normal mode of addition of the relatively weakly acidic thiols is by the electrophilic pathway in accordance with Markovnikov s rule (equation 299). However, it is established that even the smallest traces of peroxide impurities, oxygen or the presence of light will initiate the free radical mode of addition leading to anti-Markovnikov products. Fortunately, the electrophilic addition of thiols is catalyzed by protic acids, such as sulfuric acid538 and p-toluenesulfonic acid,539 and Lewis acids, such as aluminum chloride,540 boron trifluoride,536 titanium tetrachloride,540 tin(IV) chloride,536 540 zinc chloride536 and sulfur dioxide.541... 

Aluminum alkyls in reactions with carbon-carbon multiple bonds, oxiranes,... 

The addition of aluminum hydride and alkyls to non-activated C-C multiple bonds (C=C or C=C) is referred to as hydroaluminaton and carboalumination, respectively. The reactions involve metathesis of each C-C multiple bond with Al-H or Al-C bonds, giving an Al-C =C-H (or Al-C-C-H) or A/-C=C-C (or A/-C-C-6) structure, respectively. These methods are of broad utility in the construction of Al-C linkages, including Al-alkenyl and Al-alkyl bonds, which can be further converted into C-C bonds (Equations (42)-(45)).192-196 Therefore, a great contribution has been made in synthetic applications, in addition to the mechanistic studies, of hydroalumination and carboalumina-tion since 1993.197-199... 

Multiple bonds involving aluminum and gallium atoms ... 

Aluminum trichloride catalyzed hydrosilation provides an interesting alternative to the free radical process. The addition of the silane was found to occur regioselectively at trisubstituted alkenes in a frans -fashion. Mechanistically it was concluded that the reaction proceeds via the addition of a silylenium cation to the multiple bond, generating the more stable (more substituted) carbocation, which abstracts a hydride from another molecule of hydrosilane (Scheme 2). ... 

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