Hydroalumination of olefins

Nickel catalysts are well-known to promote hydroalumination of olefins, and the resulting organoaluminum compounds can be converted to the corresponding alcohols through oxidation with molecular oxygen [97J. 

In view of the weak affinity of the ionic A1—H bond for olefins [15-21], the hydroalumination of olefins has been studied extensively in the presence of transition metal catalysts. Among these, only Ti and Zr catalysts have proved to be effective for obtaining hydroalumination products and their subsequent functionalization with various... 

The cis-stereochemistry of the hydroalumination of olefins is proved by the reaction of a strained cycloolefin, 1,1-dimethylindene, with i-Bu2AlD in the presence of Et20 (to slow down the inversion process of the Al—C bond). The deuterolysis of the Al—C bond (retention of configuration) leads to pure cis-2,3-dideuterio-l,l-dimethylindane ... 

Volume E21 D.2.5.2. Hydroboration and Hydroalumination of Olefinic Double Bonds... 

Aluminium and Thallium.—The main new reactions of organoaluminium compounds in C—C bond-forming processes continue to depend on four-co-ordinate aluminate complexes. Scheme 8 depicts some of the new reactions based on aluminates derived by hydroalumination of olefins using LiAlH4-... 

The well-known hydroalumination of olefins with dialkylaluminium hydrides can be extended to the addition of diethylaluminium chloride. With diphenylpropene the intermediate (332) is formed, together with ethylene, and yields l,l-diphenylpropan-2-ol in 90% yield on oxidation with H2O2. 

The retrosynthetic elimination of olefinic stereocenters (E or Z) was illustrated above by the conversion 147 => 148 under substrate spatial control. It is also possible to remove olefinic stereocenters under transform mechanism control. Examples of such processes are the retrosynthetie generation of acetylenes from olefins by transforms such as trans-hydroalumination (LiAlH4), ci5-hydroboration (R2BH), or ci -carbometallation... 

The reaction may proceed via the hydroalumination of the olefin moiety to give 15, which can undergo [3-alkoxy elimination to yield, upon workup, the alcohol 16. How-... 

M. Zaidlewicz, Formation of C—H Bonds by Reduction of Olefinic Double Bonds—Hydroboration and Hydroalumination, in Methoden Org. Chem. (Houben-Weyl) 4th ed. 1952-, Stere-... 

An enantioselective hydroalumination of a prochiral olefin was first reported by GiacomeUi and coworkers. The authors surveyed a number of chiral amines in the nickel catalyzed hydroalumination of 1,1-disubstituted alkenes. Of the amines examined, N,N-dimethylmenthylamine (DMMA) in combination with triisobutylalane and catalytic amounts of Ni(mesal)2 (mesal = methylsaHcyHde-neimine) (5) effected the hydroalumination of 2,3,3-trimethylbutene which, fol-... 

The conditions required for the reactions (a), (b) and (d) (autoclave, high H2 and olefin P) are not suitable for laboratory work. However, alkylaluminates can be prepared by the hydroalumination of multiple C—C bonds with LiAlH4 in the presence of transition-metal salts in tetrahydrofuran (THF) ... 

Hydroalumination of nonterminal olefins may be accompanied by isomerization to the terminal olefins, depending on the Al—H Ti ratio . The tetraalkylaluminates accessible via reaction (e) or (f) are useful in organic synthesis " . 

Exceptions are styrene (25 % nonterminal) and Et3SiCH=CH2 (70% nonterminal) . The hydroalumination of Mc3SiCH=CH2 with i-BujAlH followed by olefin displacement (see 5.3.3.4.2) leads to a single product ... 

In the hydroalumination of cyclic olefins with i-Bu2AlH the cis-addition in donor solvents is kinetically controlled . For indenes, polar effects are noticable, whereas steric effects are most important for 1-substituted acenaphtenes . The regiochemistry of the addition is controlled by steric effects except for trimethylsilyl substituents . The... 

Formation of C-H Bonds by Reduction of Olefinic Double Bonds via Hydroboration and Hydroalumination... 

More recent studies describe treatment of alcohols 189 with a CuI/LAH mixture, ostensibly providing a CuH reagent to effect a net Sn2 delivery, thus, placing hydrogen in a stereodefined allylic position (Eqn. 1-13). Secondary alcohols invariably gave products of -configuration. CuI/LAD mixtures led to >95 /o incorporation of deuterium. Hydroalumination of the strained olefin is not a competing side reaction in this chemistry. 

The hydroalumination of 1-olefins with LiAlH, followed by treatment with 3-bromoprop-l-yne in the presence of a catalytic amount of CuCl results in the coupling reaction shown in Scheme 16, the method is general for the synthesis of terminal alkenes. A closely related reaction. Scheme 17 gave terminal... 

The data presented in the literature indicate that in most cases, catalytic hydroalumination of acetylenes occurs under mild conditions to give alkenyl alanes, which are hydrolyzed to give Z-olefins in high yields. 

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