Conventional syntheses

Ge(CF3)4 and Sn(CF3)4 in 1975, many authors had given detailed reasons for the supposed instability of these species as a rationale for the failure of conventional syntheses to produce them. 

Previously, trifluorosilyl groups have been bound to phosphorus (40) and silicon via the SiF (g), fluorine-bond insertion-mechanism (41). The new compound HgCSiFs) is readily hydrolyzed, but it can be stored for long periods of time in an inert atmosphere. It is a volatile, white solid that is stable up to at least 80°C. The preparation of bis(trifluoro-silyDmercury, of course, raises the possibility of (a) synthesis of the complete series of trifluorosilyl, "silametallic compounds, as had previously been done for bis(trifluoromethyl)mercury by using conventional syntheses, and (b) transfer reactions similar to those in Section II, as well as (c) further exploration of the metal-vapor approach. The compound Hg(SiF.,)j appears also to be a convenient source of difluoro-silane upon thermal decomposition, analogous to bis(trifluoromethyl)-mercury ... 

Fine chemicals are often manufactured in multistep conventional syntheses, which results in a high consumption of raw materials and, consequently, large amounts of by-products and wastes. On average, the consumption of raw materials in the bulk chemicals business is about 1 kg/kg of product. This figure in fine chemistry is much greater, and can reach up to 100 kg/kg for pharmaceuticals (Sheldon, 1994 Section 2.1). The high raw materials-to-product ratio in fine chemistry justifies extensive search for selective catalysts. Use of effective catalysts would result in a decrease of reactant consumption and waste production, and the simultaneous reduction of the number of steps in the synthesis. 

Ordinary chemical reactions have their scopes and limitations for various reasons. Many sterically crowded products cannot be formed by conventional syntheses, but they can still be prepared by the U-4CR. Thus, the product 22 ° can be formed only by the U-4CR, (Scheme 1.8). 

The protons released are presumably available to compensate for the loss of the charge balancing cations within the zeolite. In conventional syntheses, the phtha-lonitrile condensation normally requires the nucleophilic attack of a strong base on the phthalonitrile cyano group [176, 177]. This function is presumably accommodated by the Si-O-Al (cation) basic sites within the ion-exchanged faujasite zeolites [178, 179]. The importance of this role is perhaps emphasized by the widespread use of alkali metal exchanged faujasites, particularly the more basic NaX materials of higher aluminium content [180, 181] as hosts for encapsulated phthalocyanine complexes. 

Since the synthesis of carbon nanotubes by Iijima [1, 2], a lot of investigations have been made on this kind of novel material [3-16]. Carbon nanotubes can be conventionally synthesized with several methods [17, 18], Recently, catalytic synthesis method has been developed to prepare carbon nanotubes on Co/Si02 [19, 20]. Hemadi et al. first extended the catalytic synthesis to the use of zeolites (NaY, HY and ZSM-5) as catalyst supports to synthesize carbon nanotubes [21]. 

Therefore, the solvent used for successful electrosynthesis of PcCu should be inert in relation to PA and, on the other hand, should have electroconductivity. The compounds used as promoters [41] could theoretically serve as such solvents. Tetramethylurea (TMU) and l-methyl-2-pyrolidinone were chosen by the authors of Ref. 32 among other promoters used in the work [41]. The first one has a nature close to that of the principal precursor (urea), and thus should not influence the reaction course negatively. The TMU has sufficient conductivity to permit electrolysis in its medium, and reasonable viscosity. The boiling point of 174-178 C is ideal for such research, since conventional syntheses of Pc from urea and PA are carried out at similar temperatures. The results of TMU use as a solvent are presented in Table 5.7. The results seem promising, and this solvent is recommended to study Pc formation in its medium in further research work. In the case of l-methyl-2-pyro-lidinone, no phthalocyanine formation was observed. No phthalocyanine was observed also in the following systems (1) urea, PA, TBA, TMU (without copper) (2) urea, PA, TBA, TMU, Sb, or Mg (anodes (3) TMU, urea (or without urea), phthalimide, TBA (in all cases with or without electrolysis). 

Trost s synthesis138 of desethylibogamine (233) illustrates the application of a new approach to alkaloid synthesis, in which the two vital cyclization processes involve catalysis by palladium complexes protection of the nitrogen by formation of an amide, so often necessary in conventional syntheses, is here unnecessary. The first of the cyclization processes, (234)—>(235), results in a very neat formation of the isoquinuclidine ring system via a palladium-catalysed SN2 cyclization of the tryptamine derivative (234) (Scheme 24). 

The syntheses of crown compounds invariably rely upon the Williamson ether synthesis, a dated but reliable reaction which is extemely useful in the synthesis of these medium-ring and large-ring compounds.7 The syntheses are usually not discussed in much detail in the literature, since the emphasis in the general area of supramolecular chemistry is on the properties of the target compounds, not on their preparation. It is frequently the case, however, that these apparently conventional syntheses are far from straightforward. 

In general, microgels obtained by radiation methods can be used in various applications in the same way as conventional synthesized systems, e.g., as drug delivery templates, for encapsulation, or as microreactors [29, 30], PAAm for example can be used as template material to synthesize hollow cadmium selenide nanospheres [24], and PVP can be used for the incorporation of ferromagnetic nanoparticles to obtain magnetic hydrogel microspheres [13],... 

The emphasis of the first two sections was the generation of novel substances. Here we note that there are advantages to the utilization of cluster precursors for solid materials for which conventional syntheses are well established. 

Except for Cp2Ru and Cp2Os the second and third row elements do not form stable isolable Cp2M compounds and conventional syntheses may lead to hydrides such as Cp2ReH or Cp2WH2 by H abstraction. A rhenocene is a dimer with a... 

Boron carbide (B4C) is one of the hardest known materials with excellent properties of low density, very high chemical and thermal stability, and high neutron absorption cross-section. Bulk B4C is conventionally synthesized by high temperature (up to 2400 °C) reactions, such as the carbothermal reduction of boric acid or boron oxide. Nanocrystalline B4C was solvothermally synthesized in CCI4 at 600 °C (Reaction (32)). 

Conventional syntheses are conversions of N > 3 different starting materials into target compounds of M > N-l preparative steps. Such sequences of reactions include the isolation and purification of intermediates and final products. After each such step, its resulting compound must be combined with the next educt, which ultimately leads to the final product. The amount of preparative work increases with each preparative step, and thus its resulting final yield decreases. 

D. Degner. Scale-Up of Electroorganic Docesses Some Examples for a Comparison of Electrochemical Syntheses with Conventional Syntheses. In Techniques of Electroorganic Synthesis, HI. 

Two additional conventional syntheses of dihydrotagetone are illustrated in Scheme 2. 

Preparative methods in which previously labeled, simple organic compounds are used in conventional syntheses. 

In boiling xylene, 0-aryl 0-methyl O-2-propynyl phosphorothioates isomerize to 0-aryl 0-methyl 5-propadienyl phosphorothioates, although with only low to moderate conversions. The anions from the conventionally-synthesized mono-thiophosphate esters (76) (R = H or Ph, = H R R = (CH2)n, n = 3 or 4) rearrange, and on subsequent alkylation or acylation (R = Me, Et, Pr, Pr , Ac, Bu CO, (PhO)2P(X), X = O, S, or Se) yield the products (77) in the (Z) configuration the latter esters undergo Diels-Alder reactions with common dienophiles (e.g. acrylonitrile, acrolein, maleic anhydride, etc.) to give the systems... 

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