Carbalumination

Figure 11 Hydroalumination and carbalumination reactions and some recent cluster derivatives.

Synthetic apphcations of double hydroalumination and double carbalumination are discussed in a recent review. ... 

Carbalumination of 271b with tri-isopropylaluminium affords acyclic products, the formation of which can be attributed to rearrangement of the initially formed cyclopropyl carbocation (equation 84). Ring-opened products also result from reactions with trialkylboranes, but only cyclopropanes, from addition to the n bond, are seen in reactions with organomagnesium reagents . 

The addition of the C—Al bond to olefinic or acetylenic substrates (carbalumination) is of interest in organometallic synthesis " . 

The carbalumination of olefins followed by displacement is valuable in organic synthesis (e.g., in the dimerization of olefins, synthesis of long-chain, terminal olefins) ... 

Intramolecular carbaluminations of olefins are facile (in the absence of ether) and show synthetic potential . This combines monohydroalumination (see 5.3.3.4.1) of nonconjugated polyenes and carbalumination leading to the synthesis of various mono- ... 

Therefore, the nature of the metal-carbon bond is important for the course of carbometallations , and carbalumination in particular. 

The carbalumination of acetylenes provides a route to alkenylaluminums. The cis addition of R3AI to HC=CH occurs under mild conditions (as compared to the addition to ethylene) for R = Et and in particular for R = i-Bu ... 

Carbalumination of disubstituted alkynes is even more difficult because it occurs only at high T. This leads to further reactions of the products initially formed. Thus, treatment of diphenylacetylene with EtjAl leads to the cis addition product ... 

Such reactions as (n) and (o) become predominant when i-BujAl is used and the tetraphenylbutadienes are obtained in good yield (75-80%) . Similarly, the products from such reactions as (m) may enter further carbalumination reactions with the... 

Intramolecular carbalumination of alkynes is observed with the dimeric diphenyl-(phenylethynyl)aluminum. The structures of such compounds are in accord with the assumption of intermediate n-complex formation between the C=C bond and Al. Carbalumination is followed by exchange, electrophilic attack at the C=C bond and a... 

Triorganoaluminums react with terminal acetylenes by alumination or carbalumin-ation (see 5.3.3.5.1). Direct metallation [see Eq. (a)] of phenylacetylene is the preferred course of reaction for Mc3Al ... 

Benzene is also evolved in cyclizations. The carbalumination product of PhjAl and diphenylacetylene loses benzene at 200°C, and 1,2,3-triphenyl-l-aluminaindene is obtained ... 

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