Acids Trimethylaluminum

CLAISEN REARRANGEMENT Alkylaluminum halides. Lithium diisopropylamide. Potassium hydride. Sodium dithionite. Titanium(TV) chloride. Trifluoroacetic acid. Trimethylaluminum. 

Trimethylaluminum, which exhaustively methylates ketones (16-27), also exhaustively methylates carboxylic acids to give tert-butyl compounds (see also 10-99) ... 

A few other successful 13C 1-NMR determinations should be mentioned. Hunt et al. [28] used 13C NMR to characterise fractions of extracted analytes of PAG and sorbitan ester samples and identified Irganox 1010. H and 13C NMR have been used to identify the main organic components of a breathable diaper back-sheet as LLDPE and pentaerythritol tetra-octyl ester (PETO) [233]. The equally present AOs Irganox 1010 and Irgafos 168 were not detected without extraction. Barendswaard et al. [234] have reported fully assigned 13C solution spectra of these two antioxidants. Chimas-sorb 944 in a polyamide matrix can be determined by H or 13C 1-NMR using solvents such as formic acid, trifluoroacetic acid or trifluoroethanol [235], Both H and 13C NMR have been used to follow the chemistry of a bis-phenoxidemethylaluminum complex (reaction product of BHT and trimethylaluminum) by exposure in air. Pierre and van Bree [216] also used 13C NMR to... 

The structure of dimethylberyllium is similar to that of trimethylaluminum except for the fact that the beryllium compound forms chains, whereas the aluminum compound forms dimers. Dimethylberyllium has the structure shown in Figure 12.3. The bridges involve an orbital on the methyl groups overlapping an orbital (probably best regarded as sp3) on the beryllium atoms to give two-electron three-center bonds. Note, however, that the bond angle Be-C-Be is unusually small. Because beryllium is a Lewis acid, the polymeric [Be(CH3)2] is separated when a Lewis base is added and adducts form. For example, with phosphine the reaction is... 

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... 

Hubbard and Miller87 used a Lewis acid catalyzed Diels-Alder reaction between y.y-disubstituted o. /i-unsaluralcd esters and cyclopentadiene in their approach toward oligomeric cyclopentanoids. In order for the reaction to proceed, they needed to add trimethylaluminum as a desiccant prior to addition of the Lewis acid catalyst aluminum trichloride. The endo/exo selectivity of the reaction with 97, depicted in equation 29, increased from 98/99 = 75/25 to 88/12 when the reaction temperature was dropped from room temperature to —20 °C. 

MAO, the most widely used Lewis acid coinitiator (activator) (Eq. 8-52), is obtained by a controlled hydrolysis of trimethylaluminum (TMA). In spite of considerable research, the detailed structure of MAO remains unclear [Chen and Marks, 2000 Kissin and Brando-lini, 2003 Pedeutour et al., 2001 Wang et al., 2001 Ystenes et al., 2000]. MAO is probably a mixture of linear, cyclic, and three-dimensional structures containing the repeat unit XXXVII with n = 5-20. 

The order of decreasing Lewis basicity toward trimethylaluminum is thiane, thiolane, diethyl (or dimethyl) sulfide, thietane and 2-methylthiirane (67IC1461). Thietane can be protonated at -60 °C with fluorosulfonic acid in antimony pentafluoride-liquid sulfur dioxide the NMR spectrum shows bands at 8 7.40 (S—H) and 3.20-4.40 p.p.m. (C—H) (71JOC1121). 

Trimethylaluminum is a colorless liquid mp 15°C, bp 127°C. It ignites spontaneously in air (pyrophoric) and decomposes violently in water. It can be stored indefinitely at room temperature under an inert atmosphere, or under its own vapor pressure, in a storage flask such as those illustrated in Fig. 4. It is a strong Lewis acid, forming many stable complexes its chemical and physical properties have been fully reviewed.11 HNMR (C6D6, rel. Me Si, 8 ppm) - 0.34(s). 

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... 

Jones and co-workers976 have recently reported the use of catalyst 49 (Figure 5.15) with perfluorinated alkanesulfonic acid sites anchored to SBA-15 as a methylaluminoxane-free supported cocatalyst for ethylene polymerization. When catalyst 49 and trimethylaluminum were used in combination with Cp 2ZrMe2 as the metallocene precatalyst, productivities as high as 1000 kg polyethylene molZr-1 h 1 were obtained without experiencing reactor fouling. 

Another regioselective addition to an epoxide was used as one step in a synthesis of the r-butyldiphenylsilyl ether (7) of verrucarinic acid from 5.3 The diol was converted into the optically active epoxy alcohol by the Sharpless method (10, 64-65) and then oxidized to the epoxy acid 6 by the new ruthenium-catalyzed oxidation of Sharpless et al. (this volume). This epoxy acid undergoes almost exclusive / -addition with trimethylaluminum to give the desired product 7. 

Tile reagent is prepared by addition of trimethylaluminum to 2,6-di-t-butyl-4-incthylphcnol in CH2C12 at - 78". After a reaction period of 30 minutes at 0°, triflic acid is added at - 78". The mixture is then stirred for 30 minutes at 0°. 

Simple alkylation can be accomplished by use of trialkylaluminums which, with Lewis acids, afford 1-C-alkyl products such as 90, available in 72% yield by reaction between di-O-acetyl-6-deoxy-D-galactal and trimethylaluminum in the presence of titanium tetrachloride in dichloro-methane at —78 °C.109 Importantly, the reaction can also be applied to 1-alkylglycals, also with high stereoselectivity, so that the doubly substituted compound 91 can, for example, be made by allylation of tri-O-acetyl-l-C-methyl-D-glucal. Its C-l epimer is available by C-methylation of the 1-C-allylglucal.110... 

A convenient synthesis of l//-indolyl-2-benzothiazoles in moderate yield by the direct conversion of indole-2- and 5-carboxylates with in situ generated trimethylaluminum-2-aminothiophenol was described. [95H1045] 2-Substituted 1,3-benzothiazoles having a variety of substituents can be prepared from 2-methylthio-N-triphenylphosphoranylideneaniline and acid chlorides by iminophosphorane-mediated cyclization. [95H455]... 

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