Titanium chloride complexes

These mixed phosphate ester titanium complexes or their amine salts are useful as fuel additives to help maintain cleanliness of carburetors and inhibit surface corrosion. Chloride-free mixed alcohol phosphate esters can be obtained if a tetraalkyl titanate is used (101). 

The advantages of titanium complexes over other metallic complexes is high selectivity, which can be readily adjusted by proper selection of ligands. Moreover, they are relative iaert to redox processes. The most common synthesis of chiral titanium complexes iavolves displacement of chloride or alkoxide groups on titanium with a chiral ligand, L ... 

A chiral titanium complex with 3-cinnamoyl-l,3-oxazolidin-2-one was isolated by Jagensen et al. from a mixture of TiCl 2(0-i-Pr)2 with (2R,31 )-2,3-0-isopropyli-dene-l,l,4,4-tetraphenyl-l,2,3,4-butanetetrol, which is an isopropylidene acetal analog of Narasaka s TADDOL [48]. The structure of this complex was determined by X-ray structure analysis. It has the isopropylidene diol and the cinnamoyloxazolidi-none in the equatorial plane, with the two chloride ligands in apical (trans) position as depicted in the structure A, It seems from this structure that a pseudo-axial phenyl group of the chiral ligand seems to block one face of the coordinated cinnamoyloxazolidinone. On the other hand, after an NMR study of the complex in solution, Di Mare et al, and Seebach et al, reported that the above trans di-chloro complex A is a major component in the solution but went on to propose another minor complex B, with the two chlorides cis to each other, as the most reactive intermediate in this chiral titanium-catalyzed reaction [41b, 49], It has not yet been clearly confirmed whether or not the trans and/or the cis complex are real reactive intermediates (Scheme 1.60). 

The pharmaceutical interest in the tricyclic structure of dibenz[6,/]oxepins with various side chains in position 10(11) stimulated a search for a convenient method for the introduction of functional groups into this position. It has been shown that nucleophilic attack at the carbonyl group in the 10-position of the dibenzoxepin structure renders the system susceptible to water elimination. Formally, the hydroxy group in the enol form is replaced by nucleophiles such as amines or thiols. The Lewis acids boron trifluoride-diethyl ether complex and titanium(IV) chloride have been used as catalysts. 

Effective 1,4-asymmetric induction has been observed in reactions between 2-(alkoxyethyl)-2-propenylsilanes and aldehydes. The relative configuration of the product depends on the Lewis acid used. Titanium(IV) chloride, in the presence of diethyl ether, gave 1,4-ijn-products with excellent stereoselectivity with boron trifluoride-diethyl ether complex, the amt-isomer was the major product, but the stereoselectivity was less83. 

Excellent chelation control was observed using tributyl(2-propenyl)stannane and a-benzyloxy-cyclohexaneacetaldehyde with magnesium bromide or titanium(IV) chloride, whereas useful Cram selectivity was observed for boron trifluoride-diethyl ether complex induced reactions of the corresponding ferr-butyldimethylsilyl ether89. 

For a-benzyloxycyclohexaneacelaldehyde and 2-butenylstannanes, good chelation control was observed using zinc iodide and titanium(IV) chloride, but only weak synjanti selectivity. Better syn/anti selectivity was found using boron trifluoride-diethyl ether complex, but weak chelation control. Magnesium bromide gave excellent chelation control and acceptable syn/anli selectivity90. 

The breakthrough was achieved with the creation of dialkoxy(tj5-cyclopentadienyl)titanium(IV) chlorides derived from sterically hindered chiral alcohols11 35,35a 36. Allyl derivatives 8 and 10, prepared in situ from complexes 7 and 9, have sufficient stability and reactivity. 

Dienones, such as 4-[4-(trimethylsilyl)-2-butenyl]-3-vinyl-2-cyclohexenone, are useful precursors for these particular transformations the allylsilane side chain is too short for effective 1,4-addition, but just right for 1,6-addition, resulting in six-ring annulation. Three different Lewis acids can be used titanium(IV) chloride, boron trifluoride diethyl ether complex, and ethylaluminum dichloride. The best chemical yields and complete asymmetric inductions were obtained with ethylaluminum dichloride. 

Tricyclic compounds can be obtained directly by annulation on to cyclic allylsilanes, using either ethylaluminum dichloride or titanium(IV) chloride as Lewis acids57. The stereochemical outcome of this particular cyclization is controlled by the relative configuration of the cyclic allylsilane. The reaction follows the usual anti" SE2 process for reactions of allylsilanes with electrophiles. Thus, the reaction was stereospecific, which makes it very useful for stereocon-trolled syntheses of complex ring systems57. 

The Lewis acid mediated addition of allylic tin reagents to nitroalkenes has been reported. The condensation reaction of tributyl[(Z)-2-butenyl]tin(IV) with (E)-(2-nitroethenyl)benzene or (L)-l-nitropropene catalyzed by titanium(IV) chloride proceeded with modest anti diastereoselectivity. Poorer diastereoselection resulted when diethyl ether aluminum trichloride complex was employed as the Lewis acid 18. 

Titanium, tetrakis(trimethysilyl)oxy-, 3, 334 Titanium, tetranitrato-stereochemistry, 1,94 Titanium, triaquabis(oxalato)-structure, I, 78 Titanium, tris(acetylacetone)-structurc, 1,65 Titanium alkoxides oligomeric structure, 2,346 synthesis ammonia, 2, 338 Titanium chloride photographic developer, 6,99 Titanium complexes acetylacetone dinuclear, 2, 372 alkyl... 

Titanium(III) chloride dissolves in water to give [Ti (H2 O). This complex ion has the absorption... 

Plugging solution for low temperature wells—contains plugging cement, water and molten chloride melt obtained as waste from titanium-magnesium production as complex chloride additive. Patent RU 1091616-C, 1995. 

Very recently, Eisch and co-workers have developed new alkylidene-group IV metal complexes such as methylidene titanium dichloride 67, readily accessible from titanium(iv) chloride and an excess of methyllithium at low temperature (Scheme 24).53 The new methylenating agent 67 can easily convert benzophenone at low temperature into 1,1-diphenylethylene in quantitative yield. 

Titanium chlorides, 25 49—50 manufacture of, 25 52—53 Titanium chloroacetate complexes, 25 96 Titanium citrates, 25 89 Titanium complexes chiral, 25 98-99... 

Titanium lactate complexes, 25 88 Titanium magnesium alloys, 13 626 Titanium-magnesium chloride recycle magnesium manufacturing processes, 15 337-338... 

Attempts to obtain alkylcarbonium complexes by dissolving alkyl chlorides (bromides) in liquid Lewis acid halides (stannic chloride, titanium (IV) chloride, antimony pentachloride, etc.) as solvent were unsuccessful. Although stable solutions could be obtained at low temperature with, for example, t-butyl chloride, the observed N.M.R. chemical shifts were generally not larger than 0 5 p.p.m. and thus could be attributed only to weak donor-acceptor complexes, but not to the carbonium ions. The negative result of these investigations seems to indicate that either the Lewis acids used were too weak to cause sufficient ionization of the C—Cl bond, or that the solvating effect of the halides... 

Nugent, W. A. (1998) Desymmetrization of meso-epoxides with halides A new catalytic reaction based on mechanistic insight, J. Am. Chem. Soc., 120 7139-7140. Bruns, S. Haufe, G. (1999) Catalytic asymmetric ring opening of epoxides to chlorohydrins with mild chloride donors and enantiopure titanium complexes.. 

Although several Lewis Acids were evaluated, including titanium(lV) chloride, aluminum(lll) chloride and tin(lV) chloride, ferric(lll) chloride proved to be the most effective co-catalyst. We believe that in the presence of a Lewis Acid, the rate of j3-palladium hydride elimination (H-Pd-X) from the -allyl carbomethoxy palladium complex 4 can be enhanced. A good leaving group such as iodide attached to -allyl carbomethoxy palladium complex 4 would facilitate iodopalladium hydride elimination to selectively form methyl, -pentadienoate (Equation 11.). 

Complexes, such as 1, also readily react with anions of amines the effect of added Lewis acids was investigated boron trifluoride-diethyl ether complex exerted little effect upon the reaction, but addition of titanium(IV) chloride or tin(lV) chloride inhibited the Michael addition45. 

The reactivity of bromine trifluoride is significantly enhanced by Lewis acids, such as tin(IV) chloride, antimony(V) chloride, titanium(IV) chloride, which are exchanged to the corresponding fluorides and give complexes with bromine trifluoride. Thus, the reaction of 2,2,2-tri-fluoroethyl or 2,2,3,3-tetrafluoropropyl 2,3-dibromopropanoate with bromine trifluoride in the presence of 1 mol% tin(IV) chloride affords the corresponding 2,3-difluoropropanoates in 85-87% yield.110... 

Titanium(IV) chloride is used as the catalyst in a Knoevenagel reaction between various 2,2-disubstituted 3-hydroxypropanals and malonic acid or its esters. The products are substituted dihydropyran-2-ones (536) (79LA751). The reaction, which occurs cleanly and in good yield, utilizes an excess of the titanium halide and is thought to involve a cyclic complex which undergoes an ester exchange to a lactone complex (Scheme 198). 

Aluminum trichloride is the most commonly used catalyst, although aluminum tribromide is more efficient.1 For the rearrangement of l-broino-2-chloro-1,L2-lrifluoroethane (3) to 2-bromo-2-chloro-l,l,l-trifhioroethane (4). none of the following Lewis acids are effective iron(III) chloride. iron(III) bromide, antimony(III) chloride, antimony(V) chloride. tin(IV) chloride, titanium(IV) chloride, zinc(II) chloride, and boron trifluoride-diethyl ether complex.1" ... 

Chromium carbene complexes, 82 Methyl acrylate, 183 (2R,4R)-Pentanediol, 237 Titanium(IV) chloride, 304 Nitroaldols Nitromethane, 199 Intramolecular reactions Methyl acrylate, 183 Other aldol-type reactions Bis(2-pyridinethiolato)tin(II), 40 Alkoxycarbonylation (see Carboalkoxy-lation)... 

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