Titanium tetrachloride synthesis

Tetraphenylethylene s. under Na Titanium tetrachloride Synthesis of ethylene derivatives from a-halogenoketones... 

The second type of solution polymerization concept uses mixtures of supercritical ethylene and molten PE as the medium for ethylene polymerization. Some reactors previously used for free-radical ethylene polymerization in supercritical ethylene at high pressure (see Olefin POLYMERS,LOW DENSITY polyethylene) were converted for the catalytic synthesis of LLDPE. Both stirred and tubular autoclaves operating at 30—200 MPa (4,500—30,000 psig) and 170—350°C can also be used for this purpose. Residence times in these reactors are short, from 1 to 5 minutes. Three types of catalysts are used in these processes. The first type includes pseudo-homogeneous Ziegler catalysts. In this case, all catalyst components are introduced into a reactor as hquids or solutions but form soHd catalysts when combined in the reactor. Examples of such catalysts include titanium tetrachloride as well as its mixtures with vanadium oxytrichloride and a trialkyl aluminum compound (53,54). The second type of catalysts are soHd Ziegler catalysts (55). Both of these catalysts produce compositionaHy nonuniform LLDPE resins. Exxon Chemical Company uses a third type of catalysts, metallocene catalysts, in a similar solution process to produce uniformly branched ethylene copolymers with 1-butene and 1-hexene called Exact resins (56). 

In this process, catalysts, such as boric acid, molybdenum oxide, zirconium, and titanium tetrachloride or ammonium molybdate, are used to accelerate the reaction. The synthesis is either carried out in a solvent (aUphatic hydrocarbon, trichlorobenzene, quinoline, pyridine, glycols, or alcohols) at approximately 200°C or without a solvent at 300°C (51,52). 

Other preparative methods include direct synthesis from the elements, reaction between gaseous hydrogen fluoride and titanium tetrachloride, and decomposition of barium hexafluorotitanate [31252-69-6] BaTiF, or ammonium, (NH 2TiFg. 

As Lewis acid, titanium tetrachloride, boron trifluoride or ethylaluminum dichloride is often used. The stereochemical outcome of the reaction strongly depends on the Lewis acid used. The Sakurai reaction is a relatively new carbon-carbon forming reaction, that has been developed into a useful tool for organic synthesis. ... 

The McMuny coupling route has been utilised by Iwalsuki and co-workers the synthesis of PDBoxTV 85 (Scheme 1-29) [129]. Dialdehyde 90 is polynn ized in the presence of titanium tetrachloride and zinc dust. Molecular weights 35000 are reported and the polymer is freely soluble in solvents such as chloi form. The reported absorption maximum (605 nm) was close to that observed I the Blohm route [I27J. 

This series of reagents is characterized by the use of metals under the appropriate conditions. In this regard, a mixture of zinc dust and titanium tetrachloride in ether provided a useful synthesis of vinyl sulphides43, with the possibility of further substitution alpha to the sulphur atom, as outlined in equation (16). The reaction is easy to carry out and gave yields of 49 to 87%, although the authors do not provide much detail of their experimental procedure and of the purity (chemical or stereochemical) of their products. 

Hansen and colleagues177 used (+)-pantolactone as a chiral auxiliary to achieve asymmetric induction in the first step toward their synthesis of d.v-perhydroisoq uinol inc 278. The titanium tetrachloride catalyzed reaction between 1,3-cyclohexadiene (275) and chiral acrylate 276 proceeded with high diastereofacial selectivity to give 277 (94% de) in 75% yield (equation 77). 

Hydrothermal Synthesis of Brookite. Typically, NaOH solution (2M) was added to 5 mL titanium tetrachloride with stirring to adjust the pH value of the solution to 10, producing a basic colloidal solution. The solution obtained was transferred into an autoclave and heated at 200°C for 24 h. The white precipitates were separated by centrifugation and washed three times with deionized water and once with ethanol. The product was dried at 70°C in air overnight and was ground to a fine powder before the deposition of gold precursor on its surface. 

An example of a chelation-controlled titanium tetrachloride-catalyzed aldol condensation has been featured in a recent synthesis of pestalotin (eq. [86]) (100). The condensation illustrated afforded... 

Another useful route to alkaloids involves the electrochemical oxidation of lactams (145) bearing functionality on nitrogen that can be used to intramolec-ularly capture an intermediate acyl im-minium ion (146). The concept is portrayed in Scheme 33 and is highlighted by the synthesis of alkaloids lupinine (150) and epilupinine (151) shown in Scheme 34 [60]. Thus, the electrooxidation of lactam (147) provided a 71% yield of ether (148). Subsequent treatment with titanium tetrachloride affected cyclization and afforded the [4.4.0] bicyclic adduct (149). Krapcho decarbomethoxylation followed by hydride reduction of both the... 

Interest in the total synthesis of the Aspergillus terreus derived quadrone fi06), an antitumor agent has been very intense. Success was first realized in Danishefsky s laboratory Once 601 was reached, its sidechain was elaborated and ring closure effected (Scheme LII). Condensation of 602 with 1-tert-butoxy-l-tcrt-butyl-dimethylsiloxyethylene in the presence of titanium tetrachloride and subsequent desilylation resulted in introduction of an angular acetic acid moiety. The two sidechains were next connected by intramolecular alkylation and the resulting keto add was subjected to selenenylation in order to produce 603. The a, P-unsaturated double bond was used to force enolization to the a position. Indeed, 604 was... 

Boron trifluoride, zinc bromide, and tin tetrachloride led to non-chelation-controlled antt -adducts 3, whereas the use of titanium tetrachloride and magnesium bromide resulted in chelation-controlled syn-adducts 2. Both adducts can be used as starting compounds for the iterative synthesis of amino sugars. 

The reaction of a-bromoacetals with trimethylsilylenolates catalyzed by titanium tetrachloride provides /3-alkoxy-y-bromoketones, which are useful furan precursors (Scheme 33) (75CL527). A new synthesis of acylfurans is exemplified by the formation of the 3-acetyl derivative (146) by heating the brdmoalkene (145) (78JOC4596). 2,2-Dimethyl-3(2//)-furanone (148) has been synthesized from 3-hydroxy-3-methylbutan-2-one treatment with sodium hydride and ethyl formate gave the hydroxymethylene derivative (147), which was cyclized and dehydrated to the furanone (148) with hydrochloric acid (Scheme 34) (71TL4891). O... 

An unusual new synthesis method involves carrying out reactions in a molten salt medium, and has been used on an industrial scale for the production of metallic nitride, carbide or carbonitride powders.25 An illustration of this CEREX process is the preparation of oxygen-free titanium nitride in molten calcium chloride. The method involves the reaction between titanium tetrachloride and calcium nitride ... 

Uses. The most important commercial use for benzonitrile is the synthesis of benzoguanamine, which is a derivative of melamine and is used in protective coatings and molding resins (see Amino RESINS Cyanamides). Other uses for benzonitrile are as an additive in nickel-plating baths, for separating naphthalene and alkylnaphthalenes from nonaromatics by azeotropic distillation (qv), as a jet-fuel additive, in cotton bleaching baths, as a drying additive for acrylic fibers, and in the removal of titanium tetrachloride and vanadium oxychloride from silicon tetrachloride. 

The synthesis of p-lactams enantiomerically pure, via a multistep Gilman-Speeter type reaction [139] has been reported to be carried out with chiral oxazo-lidinones [140]. Titanium tetrachloride mediated condensation with imine gave an intermediate p-amino acyloxazolidinone, the major diastereomer of which could readily be purified by Si02 chromatography. Silylation and fluoride catalyzed cyclization gave the final p-lactam (Scheme 53). 

Synthesis of 1,3-dithietanes may be performed using several routes. They can be obtained by an intramolecular cyclization of dithiocarbonates <2003CC1408>. The cyclization of the ethoxycarbonylsulfonyl derivatives 155 catalyzed by titanium tetrachloride in dichloromethane at room temperature afforded the corresponding derivatives 156 in satisfactory yields (Equation 20 Table 6). 

Periodic TMPhT production (Fig.80) comprises the following main stages the production of sodium hydroxide solution in methyl alcohol the preparation of oligo-a-sodiumoxy-o)-hydroxymethylphenylsiloxanes the preparation of titanium tetrachloride solution in benzene the synthesis of TMPhT the filtration of TMPhT from sodium chloride the distillation of the solvent and extraction of TMPhT the filtration of TMPhT, the product. 

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