Acids Triisobutylaluminum

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. 

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... 

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). 

Trialkylaluminums, 204 Trichloroisopropoxytitanium, 300 Triisobutylaluminum, 205 Trimethylaluminum, 205 Trityl perchlorate, 339 Trityl tetrafluoroborate, 301 Zinc bromide, 349 Zinc chloride, 44, 108, 181, 190, 349 Zinc iodide, 88, 112, 280, 349, 350 Zirconium(IV) acetylacetonate, 351 Zirconium(IV) chloride, 16 Zirconium(IV) isopropoxide, 311 Other Organic and Inorganic Acids Acetic acid, 45 Benzoic acid, 312 Camphor-10-sulfonic acid, 62, 64 Formic acid, 137... 

Triethylaluminum, 204 Triisobutylaluminum, 205 Trimethylaluminum, 22, 205 Vilsmeier reagent-Lithium tri-r-butoxy-aluminum hydride, 342 Boron Compounds Alkyldimesitylboranes, 8 Allenylboronic acid, 36 9-Borabicyclo[3.3.1]nonane, 92 Borane-Dimethylamine, 42 Borane-Dimethyl sulfide-Sodium borohydride, 25... 

Trifluoromethyl iodide, 599 Trifluoromethylzinc iodide, 599 Trifluoroperacetic acid, 560 Triisobutylaluminum-bis(N-... 

A wide range of trialkylaluminum with different bulkiness and Lewis acidity was investigated They influenced differently the PMMA tacticity. EtsAl and i-BusAl led to syndiotactic PMMA, whereas atactic PMMA was formed in the presence of f-BusAl. Ballard and coworkers successfully polymerized MMA in toluene at 0 °C in the presence of a mixture of f-BuLi and (2,6-di-f-butyl-4-methylphenoxy)diisobutylaluminum, that was prepared by reaction of triisobutylaluminum with 2,6-di-f-butyl-4-methylphenol. In order to shed light on the origin of the polymerization control, a mechanistic study was undertaken by NMR techniques. In the f-BuLi/EtsAl system, the actual polymerization initiator is a f-butyl carbanion. Actually, f-BuLi forms an ate complex with EtsAl. Later on, Muller and coworkers analyzed the unimeric model in the presence of EtsAl and MMA, and they confirmed the formation of a bimetallic ate complex It was accordingly proposed that the propagating species is an ate complex, which exhibits a decreased nucleophilicity compared to the uncomplexed species. 

Some aluminum Lewis acids such as triisobutylaluminum exhibited a rate enhancing effect in the oxazaborolidine-catalyzed borane reduction of ketones... 

Somewhat higher ees were also obtained in the presence of triisobutylaluminum. However, addition of titanium Lewis acids such as Ti(0-i-Pr)4 or TiCl4 resulted in the complete lose in enantioselectivity. 

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