Titanium lV Chloride

On the other hand, in the presence of Lewis acids such as titanium(lV) chloride or eerium(TIT) chloride, the (S)-e s-conformer predominates via chelation of the two carbonyl groups and a reversed stereochemistry of the addition reaction is observed1 °. 

These observations were explained in terms of an SE reaction between the 2-butenyl-(tributyl)stannane and tin(IV) chloride, which competes with Lewis acid catalyzed carbonyl attack. The 1 -methyl-2-propenyltin trichloride so formed reacts with the aldehyde to give linear products, or isomerizes to give the more stable ( )- and (Z)-2-butenyltin trichlorides which then react74. Similar results were obtained with titanium(lV) chloride, except that the anti-ad-duct was the major product from the butenyltitanium intermediate74. 

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. 

Distilla lion of the starting materials prior to use and reactions arc carried out under nitrogen or argon with exclusion of moisture. 47.5 g (0.25 mol) of titanium(lV) chloride are added dropwise to a solution of 213 g (0.75 mol) of tetraisopropoxytitanium in 250 mL of anhyd hexane cooled by an ice-bath. The mixture is allowed to warm to r.t. and brought to a total volume of 1.0 L by dilution with hexane. The flask is sealed by a scrum cap and the stock solution handled with a syringe when used. 

The same stereochemical result is obtained when the horyl cnolate 4, derived from sultam 1 is transmetalated by the addition of titanium(lV) chloride and subsequently reacted with aldehydes106g. 

A straightforward method for aldolizing unsymmetrical ketones on the more hindered side involves the use of catalytic titanium(lV) chloride in toluene at room temperature. For examples using acyclic and cyclic ketones, and linear, branched, and aromatic aldehydes, the regioselectivity varied from 7 1 to >99 1, while the symanti ratios were moderate to good, and yields were in the range 62-91%. In contrast to other methods, base is not required, and the ketone can be used as is (i.e. the silyl enol ether is not required). 

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.). 

Pentafluorocthyl iodide is of practical interest, particularly as a precursor of higher perfluoroal-kyl iodides. There are several patents for the preparation of the key compound from tetra-fluoroethene, iodine pentafluoride and iodine at 75-80 C in the presence of catalysts anti-mony(III) fluoride, titanium(lV) chloride, boron trifluoride, vanadium(V) fluoride, niobium(V) fluoride, and molybdenum(Vl) fluoride.11-13 The agents iodine monofluoride" and bromine monofluoride" can add to branched pcrfluoroalkcnes, e.g. perfluoro-2-methylbut-2-ene gives perfluoro-2-iodo-2-methylbutane.1415... 

HOMOALLYLIC ALCOHOLS B-Allyldiisopino-campheylborane. Allyl phenyl selenide. Allyltri-/i-butyltin. Chromium(II) chloride. Crotyltrimethylsilane. Diethylftributyl-stannyl)aluminum. (2R,4R)-Pentanediol. Pinacol chloromethaneboronate. Tin-Aluminum. Titanium(lV) chloride. 

Metals with high oxidation numbers tend to act somewhat like nonmetals. For example, many transition metals form oxoanions, such as permanganate ion, chromate ion, and dichromate ion, in which the metal is covalently bonded to oxygen. The ability to form covalent bonds to oxygen is evidence of these metals more covalent nature. (In their low oxidation states, most metals typically exist in ionic compounds as monatomic cations.) Titanium(lV) chloride is an example of a compound in which the... 

The generation of chlorofluorocarbene from trichlorofluoromctliane has been achieved with biityllithium at low temperatures (— 116 0, and at 0 C with reduced titanium formed from the reaction of titanium(lV) chloride with lithium aluminum hydride. 

A procedure was introduced by Baker that involves the formation of the halose in situ by addition of titanium(lV) chloride to a solution of peracylated sugar and the mcrcurio-substitut-ed purine.Many nucleosides have been synthesized by this variant of the heavy metal salt glycosylation procedure for a review see ref 145. 

Halides of metals tend to be ionic unless the metal has an oxidation number greater than +2. For example, sodium chloride and copper(ll) chloride are ionic compounds with high melting points, whereas titanium(lV) chloride and iron(lll) chloride sublime as molecules. 

Commercial titanium(lV) chloride is prepared by the chlorination of titanium(IV) oxide ... 

The use of titanium(lV) chloride as a mediator of organic reactions (review [3045]) has recently been extended to the Dieckmann condensation, which is normally base-catalysed. In this example, an intermediate in the synthesis of piroxicam is synthesized in a reaction which gives the best yield when the substrate TiCli amine ratio is 2.2 1 3. 

The acrylate Is adds to cyclopentadiene (2) affording the corresponding adduct 3s with a d.r. >99.5 0.5, and its addition to 1.3-butadiene in the presence of titanium(lV) chloride produces the (7 )-cyclohexenyl ester in excellent chemical and optical yields (98% d.r. >97.5 2.5)17. This crystalline acrylate constitutes the first example of a dienophile bearing an auxiliary fulfilling most of the precited prerequisites. The increased efficiency exhibited by Is vs. lr is caused by the fact that the ether side chain is forced closer to the acrylate by the methyl group at C-10. 

Very recently, an intramolecular version with a related bifunctional system, activated by titanium(lV) chloride, has been reported. The civ-fused product is obtained as a mixture of stereoisomers, the ratio of which depends on the vinylic substituent X13. 

Methoxymethyl vinyl ketone undergoes titanium(lV) chloride/titanium tetraisopropoxide catalyzed cycloaddition to either stereoisomer of 1-phenylpropene to give a mixture of the two cyclobutanes which could be equilibrated to the rrans.rrans-isomer with carbonate42. 

The purity of several highly reactive substances, such as titanium(lV) chloride, was obtained in a special freezing-point apparatus developed by Glasgow and Tenenbaum (28). The freezing point of titaniumUV) tetrachloride under saturation pressure with zero impurity was calculated to be -24.10 0.0 l°C. 

Samarium selenides. Reductive cleavage of ArSeSeAr by samarium is catalyzed by a great number of metal halides bismuth(III) chloride, cadmium chloride, chromium(IIl) chloride, cobalt(II) chloride, potassium iodide, and titanium(lV) chloride. The resulting samarium arylselenides readily react with various organic halides. 

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