Using titanium trichloride

Reduction to the corresponding dediazoniated pyrazoles was achieved by using titanium trichloride or iron(II)ammonium sulfate (79S194). The yields are moderate with ammonium sulfate and higher with titanium trichloride. The exothermic reaction that takes place with development of nitrogen is somehow slower with the iron salt, but can be completed by... 

The contribution of chain transfer with OAC in the case of TiCl4/MgCl2 is insignificant since the type and concentration of OAC do not influence the molecular mass of polyethylene >. Using titanium trichloride, the contribution of chain transfer with AlEtj increases with decreasing polymerization temperature, and at 50 °C chain transfer becomes the dominating process Mn propylene polymerization its contribution is several times lower... 

As mentioned earlier, the incorporation of a higher boiling secondary amine, such as pyrrolidine or piperidine, can result in significant improvement in both shorter reaction time and increased indole yield. The examples shown in Scheme 4 [25-27,29-35,40-48] involve the use of pyrrolidine as an amine additive, and, unless otherwise noted, the yields are overall from the appropriate o-nitrotoluene, usually in one pot. Rapoport s syntheses of four bromoindoles 25 used zinc in acetic acid in the second step [26], whereas Ayer used titanium trichloride to obtain 6-bromoindole... 

Reduction. Just as aromatic amine oxides are resistant to the foregoing decomposition reactions, they are more resistant than ahphatic amine oxides to reduction. Ahphatic amine oxides are readily reduced to tertiary amines by sulfurous acid at room temperature in contrast, few aromatic amine oxides can be reduced under these conditions. The ahphatic amine oxides can also be reduced by catalytic hydrogenation (27), with 2inc in acid, or with staimous chloride (28). For the aromatic amine oxides, catalytic hydrogenation with Raney nickel is a fairly general means of deoxygenation (29). Iron in acetic acid (30), phosphoms trichloride (31), and titanium trichloride (32) are also widely used systems for deoxygenation of aromatic amine oxides. 

The primary use of TiCl is as a catalyst for the polymerisa tion of hydrocarbons (125—129). In particular, the Ziegler-Natta catalysts used to produce stereoregular polymers of several olefins and dienes, eg, polypropylene, are based on a-TiCl and A1(C2H3)3. The mechanism of this reaction has been described (130). SuppHers of titanium trichloride iaclude Akso America and Phillips Petroleum ia the United States, and Mitsubishi ia Japan. 

Reduction. Triaryknethane dyes are reduced readily to leuco bases with a variety of reagents, including sodium hydrosulfite, 2inc and acid (hydrochloric, acetic), 2inc dust and ammonia, and titanous chloride in concentrated hydrochloric acid. Reduction with titanium trichloride (Knecht method) is used for rapidly assaying triaryknethane dyes. The TiCl titration is carried out to a colorless end point which is usually very sharp (see Titanium COMPOUNDS, inorganic). 

Erom 1955—1975, the Ziegler-Natta catalyst (91), which is titanium trichloride used in combination with diethylaluminum chloride, was the catalyst system for propylene polymerization. However, its low activity, which is less than 1000 g polymer/g catalyst in most cases, and low selectivity (ca 90% to isotactic polymer) required polypropylene manufacturers to purify the reactor product by washing out spent catalyst residues and removing unwanted atactic polymer by solvent extraction. These operations added significantly to the cost of pre-1980 polypropylene. 

A further example employing displacement of a suitably activated hydroxyl group rather than halogen is also shown in Scheme 10. The use of titanium trichloride in the final step... 

Chemicals or from Merck i Company, Inc., but can also be prepared by dissolving metallic titanium in 20% aqueous hydrochloric acid or by dissolving solid titanium trichloride in 1 M aqueous hydrochloric acid. Titanium Ill) sulfate (from BDH Chemicals Ltd.) can also be used. All... 

Titanium trichloride [7705-07-9] M 154.3, m >500 , pKj 2.55 (for hydrolysis of Ti to TiOH ). Brown purple powder that is very reactive with H2O and pyrophoric when dry. It should be manipulated in a dry box. It is soluble in CH2CI2 and tetrahydrofuran and is used as a M solution in these solvents in the ratio of 2 1, and stored under N2. It is a powerful reducing agent. [Inorg Synth 6 52 I960, Synthesis 833 7989.]... 

In order to overcome the poor electrophilicity ofimines, nitrones arc used as partners for reaction with iron acyl enolates 428. Benzaldehyde phenylnitrone (5) reacts rapidly with the aluminum-based enolate at —78 C to give a crude /J-hydroxyamino iron acyl 6 (68% yield). Treatment with aqueous titanium trichloride in tetrahydrofuran at room temperature causes a selective reduction of the N—O bond and affords the /1-amino iron acyl 7 with inverse configuration compared to the addition ofimines (99% yield d.r. 11 23). 

A 3 -benzyloxy ketone gives preferential 2,2 -syn stereochemistry through a chelated TS for several titanium enolates. The best results were obtained using isopropoxytitanium trichloride.112 The corresponding /(-boron enolate gives the 2,2 -anti-2,3-anti isomer as the main product through a nonchelated TS.110... 

Natta A process for polymerizing propylene and other higher olefins, catalyzed by crystalline titanium trichloride and an alkyl aluminum compound such as triethyl aluminum. The polymer can exhibit various types of stereoregularity, depending on the catalyst and the conditions. Invented in 1954 by G. Natta at the Istituto de Chimica Industrial del Politecnico di Milano, Italy, and commercialized in 1957. Now used widely, worldwide. See also Ziegler, Ziegler-Natta. 

Reduction of aromatic aldehydes to pinacols using sodium amalgam is quite rare. Equally rare is conversion of aromatic aldehydes to alkenes formed by deoxygenation and coupling and accomplished by treatment of the aldehyde with a reagent obtained by reduction of titanium trichloride with lithium in dimethoxyethane. Benzaldehyde thus afforded /ra/is-stilbene in 97% yield [206, 209]. 

A modified procedure suitable for intramolecular reductive coupling is achieved using low-valence titanium prepared by reduction of titanium trichloride with a zinc-copper couple followed by the extremely slow addition of ketone to the refluxing reaction mixture (0.0003 mol over a 9-hour period by use of a motor-driven syringe pump) [S60. ... 

The use of C-labeled triethylaluminum allowed us to demonstrate that the quantity of —C2HB groups [deriving from A1(C2Hb)3] which is bound to the non-atactic polymer at the end of the polymerization, when operating with a constant amount of titanium trichloride, is a linear function of the square root of the alkylaluminum concentration (Fig. 22), in the considered range of experimental conditions (4 ). Similar results have been obtained by analyzing the fraction of amorphous polymer (Fig. 23) (38). 

In both cases the determination of active centers has been performed by means of absorption tests of C-labeled alkylaluminum on samples of ground a-titanium trichloride. In the first case, two a-TiCh samples were used, one of them (sample A) having low catalytic activity, the other one (sample B) high activity. In the second case, only the sample A was used, and the determination of active centers was also made by a kinetic method, still using labeled alkylaluminum. 

It has been pointed out that the product obtained by treating certain samples of ground a-titanium trichloride (particularly those which contain traces of TiCU or other Ti(IV) compounds) with radioactive alkylalu-minum, shows a certain degree of radioactivity also after submitting it to the action of an acid or an alcohol in an attempt to decompose the metal-carbon bonds. Such radioactivity is due to a contaminant, the nature of which depends on the degree of purity and the amount of crude a-titanium trichloride employed. It generally decreases, eventually attaining very low values if the crude a-titanium trichloride is repeatedly washed with anhydrous benzene before its use. 

When other samples of a-titanium trichloride are used, for instance, unground a-titanium trichloride (sample B, see Fig. 7), having a high catalytic activity, we do not observe radioactive contamination. Other types of contamination due, for instance, to the incomplete removal of alkylaluminum from the pol3nner or to secondary reactions of its alkylation, are not present in the reported tests. 

In the interval 70-100°, by using the sample A of a-titanium trichloride, all ethyl groups, initially bound to the a-titanium trichloride surface, were later found in the obtained polymer. 

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