Tetrakis titanium, reactions

The first practical method for asymmetric epoxidation of primary and secondary allylic alcohols was developed by K.B. Sharpless in 1980 (T. Katsuki, 1980 K.B. Sharpless, 1983 A, B, 1986 see also D. Hoppe, 1982). Tartaric esters, e.g., DET and DIPT" ( = diethyl and diisopropyl ( + )- or (— )-tartrates), are applied as chiral auxiliaries, titanium tetrakis(2-pro-panolate) as a catalyst and tert-butyl hydroperoxide (= TBHP, Bu OOH) as the oxidant. If the reaction mixture is kept absolutely dry, catalytic amounts of the dialkyl tartrate-titanium(IV) complex are suflicient, which largely facilitates work-up procedures (Y. Gao, 1987). Depending on the tartrate enantiomer used, either one of the 2,3-epoxy alcohols may be obtained with high enantioselectivity. The titanium probably binds to the diol grouping of one tartrate molecule and to the hydroxy groups of the bulky hydroperoxide and of the allylic alcohol... 

A reagent more reactive than tris(dimethylamino)arsine employed by Weingarten and White 39) was tetrakis(dimethylamino)titanium (145). With this compound it was possible to prepare N,N-dimethyl(l-isopropyl-2-methylpropcnyl)amine (147) from diisopropyl ketone. Weingarten and White 39) have suggested a possible mechanism for this reaction (see p. 88). If benzaldehyde 39,111), formaldehyde 111), or acetaldehyde 39) is used, the corresponding gem diamine or aminal (143) is formed. 

Chlorotris(diethylamino)titanium24 is prepared directly from diethylamine, lithium and tilani-um(IV) chloride in the presence of styrene as reducing agent25. However, a metathesis reaction between tetrakis(diethylamino)titanium26 28 and titanium(lV) chloride gives a cleaner product and is thus preferred. Bromotris(diethylamino)titanium is prepared similarly7,29. 

Reaction of tetrakis-diethylamino titanium (TDEAT) or tetrakis-dimethylamino titanium (TDMAT) with ammonia (NH3) at 300°C in a flow of helium. Possible carbon retention. 

MOCVD Reactions. A great deal of interest has been generated by the availability of two metallo-organic titanium compounds, tetrakis-diethylamino titanium (TDEAT) andtetrakis-dimethylamino titanium (TDMAT). These precursors make possible the deposition of TiN at lower temperature.[ " k l These compounds are liquid at room temperature. A flow of helium bubbling through the warm precursor entrains the vapor into the deposition chamber. Deposition temperature is approximately 320°C. The following reactions occur ... 

Interaction of anhydrous hydrazine and titanium isopropoxide is explosive at 130° C in absence of solvent. Evaporation of solvent ether from the reaction product of tetrakis(dimethylamino)titanium and anhydrous hydrazine caused an explosion, attributed to formation and ignition of dimethylamine. /V-Metal derivatives may also have been formed. 

MCM-41 (1060 30m g ) with a narrow distribution of pore diameters, centered around 3.2 nm, was chosen as support. Tetrakis(neopentyl)titanium, TiNp4 (1), reacts with this support to form =SiO-TiNp3 (2a) and (=SiO)2TiNp2 (2b). The reaction leads to a more important proportion of bis-siloxy surface species, 2b, than on non-porous Aerosil silica (Scheme 2.8). 

Reaction of tris(dimethylamino)arsine or tetrakis(dimethylamino)-titanium with aldehydes or ketones to give enamines [164, 165]. 

D. Reaction of Aliphatic Amides with Tetrakis(dimethylamino)titanium. . 1318... 

In 1966, Weingarten and White93 reported a simple route to simple 1,1-enediamines. Under mild conditions, aliphatic amides underwent reaction with tetrakis(dimethylami-no)titanium (60) to afford 1,1-enediamines 61. The reaction could be carried out with most of the common acid derivatives such as free acid, ester and anhydride via the amide (equation 22). A probable mechanism involving intramolecular dehydration has been proposed in Scheme 442. 

It has been involved in many industrial explosions. Explodes on contact with aluminum + barium nitrate + potassium nitrate + water. Forms explosive mixtures with aluminum powder + titanium dioxide, ethylene glycol (240°C), cotton lint (245°C), furfural (270°C), lactose, metal powders (e.g., aluminum, iron, magnesium, molybdenum, nickel, tantalum, titanium), sulfur, titanium hydride. Reaction with ethanol + heat forms the explosive ethyl perchlorate. Violent reaction or ignition under the proper conditions with aluminum + aluminum fluoride, barium chromate + mngsten or titanium, boron + magnesium + silicone rubber, ferrocenium diammine-tetrakis(thiocyanato-N) chromate(l —), potassium hexacyanocobaltate(3—), A1 +... 

A stereochemical control of the Ugi reaction can be effected with carbohydrates as chiral templates (e.g. tetrakis(O-pivaloyl)galactosylamine), which gives rise to easily separable amides. From these a variety of non-natural amino acids can be derived after acidic hydrolysis. The Passerini reaction, related to the Ugi rearrangement, gives a-hydroxyamides. A modification of this reaction using titanium tetrachloride gives a-branched amides in high yields via C-metalated imidoyl chlorides (equation 38). 

Tetrakis(dimethylamino)titanium converts DMF to tris(dimethylamino)methane (529 equation 236). This compound is also formed in the reaction of V-tetramethyloxamide with the titanium reagent, whereas amides which have a-CH bonds are converted to ketene aminals. Cyclic and spitocyclic compounds, containing the substitution pattern of a trisamino compound, are formed in the reaction of IVA -dialkylformamides or A/ -aryl-(VJV-dialkylformamidines with aryl isocyanates. Similar compounds, e.g. (530 equation 237), are produced in the reaction of imidazolines or lactamid-ines with isocyanates. 

Ylides Coordinated to Transition Metals. - Complexes of a-keto-stabilised ylides with early transition metals have been reported by Spannenberg et al The reaction of tetrakis(dimethylamino)titanium(IV) and benzoyltriphenyl-phosphonium bromide (48) produces complex (49) (Scheme 5) whose structure... 

Other use of the functionalized chiral BINOL includes the 5,5, 6,6, 7, 7, 8,8 -octahydro derivative developed by Chan and coworkers, the titanium complex of which is more effective than BINOL in the enantioselective addition of triethylaluminum and diethylzinc a 4,4, 6,6 -tetrakis(perfluorooctyl) BINOL ligand developed for easy separation of the product and catalyst using fluorous solvents for the same zinc reaction an aluminum complex of 6,6 -disubstituted-2,2 -biphenyldiols used by Harada and coworkers in the asymmetric Diels-Alder reaction a titanium complex of (5 )-5,5, 6,6, 7,7, 8,8 -octafluoro BINOL employed by Yudin and coworkers in the diethylzinc addition, in the presence of which the reaction of the enantiomeric (/f)-BINOL is promoted . 

Tetrakis(dimethylamino)titaiiium, Ti[N(CH3)2]4 [1, 1142, before Tetrakis-phos-phorus trichloride-nickel(O)]. Mol. wt. 225.20, orange liquid, b.p. 5070.05 mm. Prepared in 85% yield by reaction of titanium tetrachloride with lithium dimethyl-amine.1... 

Tetrakis(hexafluoroisopropoxides) of titanium, zirconium, and hafnium have been prepared by the reaction of sodium hexafluoroisopropoxide in an excess of hexafluoroisopropyl alcohol with the anhydrous metal chloride, and the spectroscopic properties are reported. The authors note that, in their experience, application to the Group IV transition metals of the previously published method for metal hexafluoroisopropoxide synthesis gives poor yields of material containing metal, fluorinated alkoxides, and co-ordinated ammonia. Dehydration of the hydrated metal chloride with methyl orthoformate and addition of hexafluoroisopropyl alcohol, followed by passage of dry ammonia through the solution, gives satisfactory yields for yttrium, lanthanum, neodymium, and erbium. 

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