Triisobutylaluminum

Early attempts by Pino and Giacomelli to resolve racemic 3,7-dimethyl-l-octene (37) by treatment with 0.3 equiv. of triisobutylaluminum in the presence of bis[(S)-seobutylsaHcyhdeneiminejnickel Ni[(S)-seobusal]2 and subsequent hydrolysis gave (S)-2,6-dimethyloctane (38) with an enantiomerical excess of 1.2% along with the unreacted starting material (S)-37 with 1.8% ee, as judged by optical rotation (Schemes 2-17 and 2-18) [28]. 

We found highly active catalysts, which are shown in Table I (3). The main component is a stable carboxylate of uranium in the oxidation state of +4, in combination with a Lewis acid and an aluminum alkyl, e.g. uranium octoate, aluminum tribromide, and triisobutylaluminum in a molar ratio of 1 0.8 25. The catalyst is usually aged for at least 2 hours at room temperature. 

The stereospecificity of the reaction depends mainly on the choice of the aluminum alkyl. If triisobutylaluminum is used as the only alkyl compound, products with very high cis contents of 98-99 % are obtained independently of the other reaction conditions. Replacement of the triisobutylaluminum by increasing proportions of triethylaluminum makes the cis content fall continuously (Figure 3). 

The same catalyst system, consisting of dineopentoxyvanadium oxychloride and triisobutylaluminum, is also suitable for the alternating copolymerization of isoprene with ethylene (20). 

Pd-catalyzed alkylations are generally rare because of the ease with which [3-hydride elimination occurs. However, alkylation of 2,4-dichloropyrimidine with trimethylaluminum in the presence of Pd(Ph3P)4 was achieved without detectable (3-hydride elimination. The preference for coupling at the 4-position was maintained for the formation of 2-chloro-4-methylpyrimidine (78), which then underwent an additional cross-coupling with triisobutylaluminum to afford 2,4-dialkylpyrimidine 79 [51]. 

Triiron dodecacarbonyl, 16 63 Triiron tetroxide, 14 542 Triisobutylaluminum, 2 345t Triisobutylaluminum... 

Sodium hydride Sodium hydrosulfite Sulfur chlorides Sulfuric acid Sulfuryl chloride Tetraethyl lead Tetramethyl lead Thionyl chloride Titanium tetrachloride Toluene diisocyanate Trichlorosilane Triethylaluminum Triethylborane Triisobutylaluminum Trimethylaluminum Trimethylchlorosilane Tripropyl aluminum Vanadium tetrachloride Vinyl trichlorosilane Zirconium tetrachloride... 

Triisobutylaluminum (TIBA) is an effective reducing agent for ketones. However, in most cases only one isobutyl group is available for reduction. Enolization occurs after a rapid reduction involving the first isobutyl group (143,147). For example, an enolate is formed in the reaction of TIBA with cyclohexanone (143) (eq. [31]). 

The structure of MAO is poorly defined and varies with preparation conditions, but it performs well in activating the metallocene initiator. The use of MAO is complicated by its lack of long-term storage stability. It is usually supplied by manufacturers as a cloudy solution of MAO in toluene MAO has very low solubility in aliphatic solvents. Precipitation is often observed on long standing, especially if the container is frequently opened and exposed to moisture and oxygen. This precipitation, if not too extensive, may not affect the utility of the MAO as a coinitiator. A modified MAO, known as MMAO, offers some improvement in storage stability and improved solubility in aliphatics. MMAO is prepared by controlled hydrolysis of a mixture of trimethylaluminum and triisobutylaluminum. 

Neat tripropylaluminum of 96% purity was supplied in a metal cylinder from Toyo Stauffer Chemical Company, Ltd. (Japan). This reagent is contaminated by 1.2% of triethylaluminura, 2.2% of triisobutylaluminum, and other compounds. Neat tripropylaluminum is also available from Aldrich Chemical Company, Inc. Since neat tripropylaluminum is pyrophoric and reacts violently with oxygen and water, the syringe should be washed with hexane immediately after addition. 

Chiral ketals of 4-alkylcyclohexanones and of m-3,5-dimethylcyclohexanone with (/ ,/ )-2,4-pentanediol are converted, on treatment with triisobutylaluminum in dichloromethane at 0°C and subsequent acetylation of the first formed alcohol with acetic anhydride, to chiral enol ethers with high yield and good diastereoselectivity82. 

High polymers are generally obtained on treatment with Lewis acids at low temperatures in an inert solvent. Boron trifluoride and boron trifluoride etherate are the most widely used catalysts, but a small amount of water must be present, which is termed a promoter triethylaluminum and triisobutylaluminum are also useful initiators and are generally used with addition of water. Alkylating agents, such as ethyl triflate, triethyloxonium tetrafluoro-borate and hexafluorophosphite, and 2-methyl-l,3-dioxolenium perchlorate, are also effective initiators (76MI51301,72MI51304). 

A 20-liter reactor was charged with 3.11 liters of triisobutylaluminum isododecane solution (110g/l) and 800 ml of 30 wt% methylalumoxane toluene solution and then stirred at 50°C for 1 hour. This mixture was then treated with dimethylsilyl (2-methyl-l-indenyl)-7-(2,5-dimethylcyclopenta[l,2-b 4,3-b-,]-dithiophene) zirconium dichloride (13.1 mmol) suspended in isododecane (500 g) and stirred 1 hour at 50°C. The reaction mixture was then diluted with 520 ml of isododecane so that the final concentration of the catalyst mixture was 100 g/1. The catalyst was then used immediately. 

Reductive rearrangement of alk-l-enyl alkyl acetals, promoted by triisobutylaluminum, stereoselectively gives 1,2-disubstituted cyclobutane derivatives. From the (S )-acetal 1, the (1. S,2.R)-cyclobulane derivative 2 is predominantly formed.39 However, the enantiomeric excess in this reaction is low because of competing racemization prior to the rearrangement. 

A RAIR spectrum of the n-butyl surface species on Al(100) has been reported at 335 K in the fCH3/pCH2 region (203). A fCH3/pCH2 RAIR spectrum has been reported for the isobutyl group formed by the decomposition of triisobutylaluminum on Al(100) at 335 K (203), and a VEEL spectrum has been obtained from decomposition of the trialkyl-aluminum on Al(lll) at 100 K (204). These alkyl surface species are stable to 450-500 K and then decompose to give the expected alkenes by /3-H elimination. 

These reactions are also quite sensitive to steric factors, as shown by the fact that if 1-butene reacts with di(jw-isoamyl)borane the initially formed product is 99% substituted in the 1-position (15) compared to 93% for unsubstituted borane. Similarly, the product obtained from hydroformylation of isobutylene is about 97% isoamyl alcohol and 3% neopentyl alcohol (17). Reaction of isobutylene with aluminum hydride yields only triisobutylaluminum. 

Triisobutylaluminum is converted to diisobutylaluminum chloride [1779-25-5] and diisobutylaluminum hydroxide [1191 -15-7]> which are used as... 

A facile synthesis of cyclobutylmethanols has been devised by reacting 2-ethoxy-5-alkyl-3,4-dihydro-2H-pyrans with aluminum alkyls (Scheme 149) (80TL4525). When (648) is reacted with triisobutylaluminum the cyclobutylmethanol (649) is formed quantitatively. While several mechanisms have been proposed for this process, initial rupture of the carbon-oxygen bond of the pyran ring to form an aluminum enolate, which then undergoes ring closure and reduction, appears to be most likely. 

---