Trimethyl aluminium, with

The Tebbe Reagent is a metal carbenoid prepared from the dimetallomethylene species derived by the reaction of trimethyl aluminium with titanocene dichloride this reagent exhibits carbenoid behaviour after the addition of a catalytic amount of pyridine. The Tebbe Reagent reacts with various carbonyl partners to give the product of methylenation ... 

Fig. 6.46. Schematic diagram of the expanding thermal plasma aixtron reactor system used at Eindhoven University of Technology to deposit PE-CVD ZnO films [51]. DEZ and oxygen are used as precursors for ZnO formation. Trimethyl-aluminium (TMA) is used as doping source. The total pressure is 2.5mbar and the substrate temperature is varied from 200 to 350°C. Reprinted with permission from [85]...

An interesting stereospecific 1,2-shift is observed upon treatment of complex (163) with trimethyl aluminium and a nucleophile (Scheme 237). Direct fluorination of chiral-complexed propargylic alcohols using DAST can be achieved in good diastereomeric excess (Scheme 238). 

Benzylic carbocations are also stabilized by complexation to chromium and a number of interesting reactions have been reported. Again, reaction of the carbocations with nucleophiles occurs from the exo face of the complex, relative to the metal. Carbocations are readily formed by treatment of benzylic alcohols with a strong acid, such as sulfuric acid, tetrafluoroboric acid, or borontrifluoride etherate. The cation can be trapped with water, alcohols, nitriles, and mono-or disubstituted amines to form alcohols, ethers, amides, and di- or trisubstituted amines respectively. Scheme 96 illustrates the formation of a benzylic carbocation followed by intramolecular trapping, resulting in a net inversion of stereochemistry. Benzylic acetates react with trimethyl aluminium introducing a methyl group from the opposite face of the metal. 

Cyclophosphinoalanes can be obtained by heating the appropriate trimethyl aluminium-secondary phosphine adduct (or the trialkyl aluminium with the phosphine) (9.138, 9.139). If higher temperatures are used, glassy polymeric materials such as (Me2P-AlMe2) may be obtained. 

Trimethyl aluminium will react with methylene trimethyl phosphorane to form a crystalline zwitterionic compound, mp = 62°C (9.148). With triphenyl or trialkyl phosphine imines in the presence of ether the products contain rings of aluminium and nitrogen (9.149). 

Trimethyl aluminium reacts with Tp M02Cl [M = Mo and W, Tp = T 3-HB(3,5-Me2pz)3] to give Tp M02Me. The tungsten-chloro complex is alkylated by RMgBr, to yield Tp W02R (R =... 

Tebbe s reagent 8.188 is a nucleophilic carbene (Scheme 8.53). It is made by treatment of titanocene chloride with trimethyl aluminium to give a chloro-bridged complex 8.187. The reagent is released in the presence of a Lewis base, such as pyridine or DMAP, which will coordinate the aluminium. Even THE can function as an effective Lewis base. 

Yamamoto and coworkers followed a promising approach, developing a rich chemistry with aluminium phenoxides prepared from sterically hindered 2,6-substituted phenols. The reaction of hullqr phenols with trimethyl aluminium led to methylaluminium bis(2,6-di-tert-bulyl-4-methylphenoxide) (MAD) and aluminium tris(2,6-diphenylphenoxide) (ATPH), as shown in Scheme 18.8, which are as expected monomeric in organic solvents. 

Another 0,0 -bidendate ligand class with a more constrained bisphenol backbone based on 2,7-dimethyl-l,8-biphenylenediol has been comprehensively investigated by the group of Ooi and Maruoka. The ligands were reacted with trimethyl aluminium as precursor to afford, after controlled alcoholysis, highly efficient aluminium catalysts, as shown in Scheme 18.14. ... 

However, a slight modification of this procedure showed that trimethyl-aluminium was available in 86% yield and 95% purity [81]. Methylalu-minium sesquiiodide was formed by direct reaction of aluminium powder with methyl iodide in ethanol. Subsequent treatment with triethylaluminium gave the triethyl derivative. 

Functionalised enones are also compatible with this methodology and easily undergo stereoselective copper-catalysed conjugate addition with trimethyl-aluminium reagents in the presence of phosphoramidite ligand L3. Thus, 1 can be converted by treatment with MesAl into the chiral ketone 2 (95% ee), which can be... 

Preparation by Friedel-Crafts acylation of phloroglucinol trimethyl ether with benzoyl chloride in the presence of aluminium chloride [753], in ethyl ether for 8 h [416]. 

Preparation by Fries rearrangement of 2,6-dichloro-phenyl mesitylenecarboxy-late (2,6-dichlorophenyl 2,4,6-trimethyl-benzoate) with aluminium chloride at 155° for 1 h (79%) [489]. m.p. 201°5-203° [489] Spectra (NA). 

Obtained by treatment of its trimethyl ether with aluminium chloride in toluene at 120° [1505]. 

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