Other Preparative Methods

The methods based on direct introduction of the heteroatom or heteroatom-containing group discussed and exemplified in the previous sections give access to a wide variety of acetylenic sulfides, selenides and tellurides. The chapter on acetylenic sulfides in ref 6 gives a review of all synthetic methods for these classes of compounds. Some of these have been illustrated by procedures in the other chapters of our book. In our selection also the effort which has to be put in the synthesis of the precursors has been taken into account. The relevant methods are represented here by schemes only. 

The addition of organolithium reagents to vinylsilanes is one of the most power- 

Grignard reagents are viable alternatives for this addition reaction, serious limita- 

The reaction presumably involves a pre-equilibrium complex of 48 and R MgX, and this makes the subsequent carbomagnesation step intramolecular in nature. The importance of this pre-equilibrium complex was further supported by the observation of dramatic solvent effects - weakly coordinating solvents such as EtgO favor this reaction whereas strongly coordinating solvents such as THF suppress it. These results may be attributed to inhibition of the formation of the pre-equilibrium complex by the coordinating solvent. 

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Other preparative methods for alkoxysilanes, in approximate order of declining utOity, are given by the following equations (34—40) ... 

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. 

Titanium Silicides. The titanium—silicon system includes Ti Si, Ti Si, TiSi, and TiSi (154). Physical properties are summarized in Table 18. Direct synthesis by heating the elements in vacuo or in a protective atmosphere is possible. In the latter case, it is convenient to use titanium hydride instead of titanium metal. Other preparative methods include high temperature electrolysis of molten salt baths containing titanium dioxide and alkalifluorosiUcate (155) reaction of TiCl, SiCl, and H2 at ca 1150°C, using appropriate reactant quantities for both TiSi and TiSi2 (156) and, for Ti Si, reaction between titanium dioxide and calcium siUcide at ca 1200°C, followed by dissolution of excess lime and calcium siUcate in acetic acid. 

Other preparative methods will be considered in Chapter 7 of Part B. 

The compounds AlYX are best prepared by direct reaction between the respective aluminum halide and chalcogenide in a sealed ampoule at 350°C. The reaction is complete after 2 weeks. In the case of the iodides, a mixture of A1 and I2 (molar ratio 3 10) is used instead of AII3. Other preparative methods, such as the reaction of an aluminum halide with Zn or Cd chalcogenide, or with the chalcogen itself, are applicable to the bromide and chloride only, and give poor yields (15-20%) (158, 159, 266, 327, 328). 

Electric discharge in a mixture of PC13 and H2 produces P2C14, and white phosphorus dissolved in carbon disulfide reacts with I2 to produce P2I4. All of the trihalides of the group VA elements are known, and they can be prepared by reaction of the elements, although there are other preparative methods. The fluorides are prepared as follows ... 

The resulting product has a low apparent density. Other synthesis techniques have been reported (192), mainly the reaction of a stoichiometric mixture of P3N5 and P4O10, heated at 780°C for 48 h, which directly results in a crystalline powder (193). Crystallization of X-ray amorphous PON produced using the other preparation methods is obtained after heating the powder in an evacuated quartz ampoule at 700-800°C for several days. 

Compounds crystallized directly onto the carbon grid or with a defined orientation, due to other preparation methods, normally exhibit a suitable initial zone close to 0°. Samples from insoluble compounds are almost statistically oriented only biased by the particle shape. In this case, it is difficult to find a single crystalline part of appropriate thickness oriented with a suitable zone parallel to the surface. The best flexibility, and therefore the best possibility to orient a zone correctly, is given by a recently developed rotation-double tilt holder (Gatan Inc.). Through the combination of rotation and additional tilt (beta tilt) it is possible to orient the tilt axis exactly even if the crystal is not sitting flat on the support film (see Fig. 4). The tilt range, dependent on the pole piece distance of the objective lens, should be at least 40°. 

Apart from the reaction of cyclohexanecarboxylic acid with methyllithium, cyclohexyl methyl ketone has been prepared by the reaction of cyclohexylmagnesium halides with acetyl chloride or acetic anhydride and by the reaction of methylmagnesium iodide with cyclohexanecarboxylic acid chloride. Other preparative methods include the aluminum chloride-catalyzed acetylation of cyclohexene in the presence of cyclohexane, the oxidation of cyclohexylmethylcarbinol, " the decarboxylation and rearrangement of the glycidic ester derived from cyclohexanone and M)utyl a-chloroj)ropionate, and the catalytic hydrogenation of 1-acetylcycIohexene. "... 

Octanol has previously been prepared from ethyl caprylate by catalytic hydrogenolysis,21 and by the Bouveault-Blanc method using sodium and alcohol in toluene.22 Other preparative methods include the reaction between fi-hexylmagnesium... 

Other Preparation Methods Organic Solvent Dilution Method... 

SOF2 is a colorless gas (bp -44°C). It was first prepared by the reaction of SOCl2 with ZnF2. Subsequently many other preparative methods have been used but the reaction of SOCl2 with SbF3 in SbFs, or with NaF in CH3CN have proved to be the best. A more recent preparation of SOF2 is by the reaction of elemental sulfur with a CL-HF mixture (125). 

Sulfilimines and sulfoximines are useful synthetic building blocks for chiral ligands and pseudopeptides. Compared to other preparation methods, the direct imination of corresponding sulfides and sulfoxides is a more convenient and straightforward synthetic route. 

Section 24.2). Other preparative methods are illustrated in the following typical examples. 

Other preparative methods of bis(trialkylsiIyl)phosphines involve reaction of RPLi2 with Me,SiCl (equation 8)28 and reaction of (Me3Si)2PLi with alkyl halides (equation 9)29. 

Preparations and reactions of some mono(trialkylsilyl)phosphines, which derived from bis(trialkylsilyl)phosphines, were described in Sections II.A and II.B. Other preparative methods of mono(trialkylsilyl)phosphines are described in Reference 10. Reactions of some mono(trialkylsilyl)phosphines with hexachloroethane or phosgene lead to chloro-phosphines (equation 42)66. It should be noted that treatment of bis(trialky lsilyl)phosphines... 

Most of the published methods for preparing gold catalysts in small research quantities are unlikely to prove suitable for commercial applications.1 Complete removal of precious metal from the liquid phase is desirable when using solution methods deposition-precipitation (DP) techniques, whilst producing highly active catalysts, also consume large quantities of water and the cost of treatment of wastewater is an expensive additional process. Other preparation methods such as appropriate modifications of impregnation via incipient wetness techniques are more likely to be suitable for commercial production if they lead to reproducible, stable... 

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