With Titanium

In 2005, Tanaka et al. [41] reported a four-component coupling process involving two acetylenes, a nitrile, and a divalent titanium tJkoxide reagent, Ti(OiPr), /2-iPrMgCl, for the synthesis of pyridines. Chiral pyridines could be synthesized by using chiral nitrile precursors. The yields were good. 

This was taken a step further with the synthesis of pyrrole units - pyrrolecarboxtildehydes - by using appropriate nitrile reagents [42]. This represented a competing method with the classic Paal-Knorr pyrrole synthesis. The scope was broad and the yields good. 

C(C02Me)2 R R2 = H, SiMeg, aryl, alkyl, CH2OH, CH20Bn 

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Reductive coupling of carbonyl compounds to yield olefins is achieved with titanium (0), which is freshly prepared by reduction of titanium(III) salts with LiAIH4 or with potassium. The removal of two carbonyl oxygen atoms is driven by T1O2 formation- Yields are often excellent even with sensitive or highly hindered olefins. (J.E. McMurry, 1974, 1976A,B). 

Form complexes with titanium, germanium, tungsten 1630-1632... 

A durable flame-retardant ceUulosic fabric with good hand is obtained by treating phosphorylated or phosphonomethylated cotton with titanium(IV) sulfate [13825-74-6] (64) ... 

Niobium is important as an alloy addition in steels (see Steel). This use consumes over 90% of the niobium produced. Niobium is also vital as an alloying element in superalloys for aircraft turbine engines. Other uses, mainly in aerospace appHcations, take advantage of its heat resistance when alloyed singly or with groups of elements such as titanium, tirconium, hafnium, or tungsten. Niobium alloyed with titanium or with tin is also important in the superconductor industry (see High temperature alloys Refractories). 

Analytical and Test Methods. o-Nitrotoluene can be analyzed for purity and isomer content by infrared spectroscopy with an accuracy of about 1%. -Nitrotoluene content can be estimated by the decomposition of the isomeric toluene diazonium chlorides because the ortho and meta isomers decompose more readily than the para isomer. A colorimetric method for determining the content of the various isomers is based on the color which forms when the mononitrotoluenes are dissolved in sulfuric acid (45). From the absorption of the sulfuric acid solution at 436 and 305 nm, the ortho and para isomer content can be deterrnined, and the meta isomer can be obtained by difference. However, this and other colorimetric methods are subject to possible interferences from other aromatic nitro compounds. A titrimetric method, based on the reduction of the nitro group with titanium(III) sulfate or chloride, can be used to determine mononitrotoluenes (32). Chromatographic methods, eg, gas chromatography or high pressure Hquid chromatography, are well suited for the deterrnination of mononitrotoluenes as well as its individual isomers. Freezing points are used commonly as indicators of purity of the various isomers. 

In galvanic coupling, titanium is usually the cathode metal and consequently not attacked. The galvanic potential in flowing seawater in relation to other metals is shown in Table 10. Because titanium is a cathode metal, hydrogen absorption may be of concern, as it occurs with titanium complexed to iron (38). 

A more recent patent describes the production of titanyl nitrate by electrolysis of titanium tetrachloride or titanyl chloride (37). Other titanium nitrogen compounds that have been described include titanous amide [15190-25-9] Ti(NH2)3, titanic amide [15792-80-0] Ti(NH)2, and various products in which amines have reacted with titanium tetrachloride (38). 

Alternatively, the TiCl may be reduced using hydrogen, sodium, or magnesium. It follows that TiCl2 is the first stage in the KroU process for the production of titanium metal from titanium tetrachloride. A process for recovery of scrap titanium involving the reaction of scrap metal with titanium tetrachloride at >800° C to form titanium dichloride, collected in a molten salt system, and followed by reaction of the dichloride with magnesium to produce pure titanium metal, has been patented (122,123). 

Titanium Dibromide. Titanium dibromide [13873-04-5] a black crystalline soHd, density 4310 kg/m, mp 1025°C, has a cadmium iodide-type stmcture and is readily oxidized to trivalent titanium by water. Spontaneously flammable in air (142), it can be prepared by direct synthesis from the elements, by reaction of the tetrabromide with titanium, or by thermal decomposition of titanium tribromide. This last reaction must be carried out either at or below 400°C, because at higher temperatures the dibromide itself disproportionates. 

Analogous with titanium tetrachloride, the tetrabromide may be made by the carbothermal bromination of titanium dioxide at ca 700°C,... 

Titanium diiodide may be prepared by direct combination of the elements, the reaction mixture being heated to 440°C to remove the tri- and tetraiodides (145). It can also be made by either reaction of soHd potassium iodide with titanium tetrachloride or reduction of Til with silver or mercury. 

Titanium Phosphides. The titanium phosphides (154) include Ti P [12037-66-0], Ti P, and TiP (163). Titanium monophosphide [12037-65-9] TiP, can be prepared by beating phosphine with titanium tetrachloride or titanium sponge. Alternatively, titanium metal may be heated with phosphoms ia a sealed tube. The gray metallic TiP is slightly phosphoms-deficient (TiPQ has a density of 408(0) kg/m, and displays considerable... 

Titanium Sulfides. The titanium sulfur system has been summarized (4). Titanium subsulftde [1203-08-6] Ti2S, forms as a gray soHd of density 4600 kg/m when titanium monosulftde [12039-07-5], TiS, is heated at 1000°C with titanium ia a sealed tube. It can also be formed by heating a mixture of the two elements at 800—1000°C. The sulfide, although soluble ia concentrated hydrochloric and sulfuric acids, is iasoluble ia alkaUes. 

Sdanediols, eg, (CgH )2Si(OH)2 and H0Si(CgH )20Si(CgH )20H, yield four-and-six-membered rings with titanium alkoxides. Pinacols and 1,2-diols form chelates rather than polymers. The more branched the diol molecule, the more likely are its titanium derivatives to be soluble and even monomeric. 

P-Diketone Chelates. P-Diketones, reacting as enols, readily form chelates with titanium alkoxides, Hberating in the process one mole of an alcohol. TYZOR AA [17927-72-9] (6) is the product mixture from TYZOR TPT and two moles of acetylacetone (acac) reacting in the enol form. The isopropyl alcohol is left in the product (87). The dotted bonds of stmcture (6) indicate electron... 

Reaction of TYZOR DC and 1,3-propanediol gives titanium 1,3-propylenedioxide bis(ethyl acetoacetate) [36497-11-7J, which can be used as a noncorrosive curing catalyst for room-temperature-vulcanizing siUcone mbber compositions (99). Similar stmctures could be made, starting with titanium bis-acetylacetonates, such as that shown in stmcture (9). 

This can be circumvented by choosing alkyl groups with no P H, eg, methyl, neopentyl, trimethylsilylmethyl, phenyl and other aryl groups, and benzyl. The linear transition state for -elimination can also be made stericaHy impossible. The most successful technique for stabilization combines both principles. The pentahaptocyclopentadienyl ring anion (Cp) has six TT-electrons available to share with titanium. Biscyclopentadienyltitanium dichloride... 

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). 

Krebs steel steel, with titanium anode cover plate titanium inlet and oudet reducer connections titanium... 

Gels. Amorphous hydrated silicas of a purity and stmcture typical of those used ia type 1 dentifrices and the liquid portion (humectant system) of type 1 dentifrices both have approximately the same refractive iadex, ie, about 1.47. As a result, the type 1 dentifrices represented ia Table 1 are inherently transparent or translucent. In the marketplace it has become popular to refer to such dentifrices as gels. For marketing reasons some companies have chosen to opacify these products, with titanium dioxide, for example. The opacified products are identical ia functionality, stmcture, and all other ways, except opacity, to their translucent or transparent counterparts. 

Transition metal-catalyzed epoxidations, by peracids or peroxides, are complex and diverse in their reaction mechanisms (Section 5.05.4.2.2) (77MI50300). However, most advantageous conversions are possible using metal complexes. The use of t-butyl hydroperoxide with titanium tetraisopropoxide in the presence of tartrates gave asymmetric epoxides of 90-95% optical purity (80JA5974). 

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