Reaction extension

Markovic N and Billing G D 1997 Semi-classical treatment of chemical reactions extension to 3D wave packets Chem. Phys. 224 53... 

Total Synthesis. Poor yields encountered duriag the manufacture of vitamin D stimulated early attempts to synthesize vitamin D. In 1959 Inhoffen synthesized vitamin from 3-methyl-2-(2-carboxyethyl)-2-cyclohexenone (40), uskig the Wittig reaction extensively (103). 

Despite all these safeguards to extend the service life of the antifreeze, fluid replacement is requited periodically. Typically, fluids are replaced because of irreversible damage caused by one of four conditions contamination, gel formation because of glycol/siUcate reaction, extensive glycol degradation caused by overheating or excessive oxygen exposure, or inhibitor depletion. 

The Bucherer carbazole synthesis was first demonstrated when 7 was heated in the presence of phenylhydrazines 8, sodium hydroxide and sodium bisulfite after acidic work-up, the benzocarbazole product 9 was isolated (-70% yield). When 2-naphthol was used the reaction was significantly slower with the yield of benzocarbazole being only 46% after several days at 130 °C Bucherer and co-workers investigated this reaction extensively concluding, incorrectly, that intermediate products were probably carbazole-Al-sulfonic acids due to the ease with which they lost the sulfonic acid residues to yield benzocarbazoles. 

Marazano and co-workers have used the Zincke reaction extensively to prepare chiral templates for elaboration to substituted piperidine and tetrahydropyridine natural products and medicinal agents. For example, 3-picoline was converted to Zincke salt 40 by reaction with 2,4-dinitrochlorobenzene in refluxing acetone, and treatment with R- -)-phenylglycinol in refluxing n-butanol generated the chiral pyridinium 77. Reduction to... 

Deady and co-workers have employed the Pfitzinger reaction extensively as a means to access diverse indenoquinolinecarboxylates as a part of a study on the latter s cytotoxicity. " ... 

Fauske, H. K., Emergenq Relief Systems Design For Runaway Chemical Reaction Extension of The DIERS Methodology, Chem. Eng. Res. Des., (67), 199-201, March 1989. 

The enolates of other carbonyl compounds can be used in mixed aldol reactions. Extensive use has been made of the enolates of esters, thiol esters, amides, and imides, including several that serve as chiral auxiliaries. The methods for formation of these enolates are similar to those for ketones. Lithium, boron, titanium, and tin derivatives have all been widely used. The silyl ethers of ester enolates, which are called silyl ketene acetals, show reactivity that is analogous to silyl enol ethers and are covalent equivalents of ester enolates. The silyl thioketene acetal derivatives of thiol esters are also useful. The reactions of these enolate equivalents are discussed in Section 2.1.4. 

The unique ability of crown ethers to form stable complexes with various cations has been used to advantage in such diverse processes as isotope separations (Jepson and De Witt, 1976), the transport of ions through artificial and natural membranes (Tosteson, 1968) and the construction of ion-selective electrodes (Ryba and Petranek, 1973). On account of their lipophilic exterior, crown ether complexes are often soluble even in apolar solvents. This property has been successfully exploited in liquid-liquid and solid-liquid phase-transfer reactions. Extensive reviews deal with the synthetic aspects of the use of crown ethers as phase-transfer catalysts (Gokel and Dupont Durst, 1976 Liotta, 1978 Weber and Gokel, 1977 Starks and Liotta, 1978). Several studies have been devoted to the identification of the factors affecting the formation and stability of crown-ether complexes, and many aspects of this subject have been discussed in reviews (Christensen et al., 1971, 1974 Pedersen and Frensdorf, 1972 Izatt et al., 1973 Kappenstein, 1974). 

Solvent-extracted delignified beech wood pulp was treated with potassium tertiary butoxide, then with quinone methides at 25 °C or 45 °C (Figure 4.13). Following reaction, extensive solvent extraction was then performed, and the modified flour was pressed to form a disc, which was then exposed to C. versicolor or G. trabeum. No indication of biological attack was found (Loubinoux etal., 1992). 

The reaction kinetics were studied on the total and separated components (graft and homopolymers) after 24-96 h of grafting at 10° C, see Fig. 7. The total yield increases almost linearly with time, and grafting is the dominant reaction. Extensive milling times has a negative effect, as the graft polymer is subjected to degradation. This was demonstrated by viscosity decreases with time. 

H Fauske, "Emergency Relief System Design for Runaway Chemical Reaction Extension of the DIERS Methodology", Chem Eng Res Dev, 67, 199-201, March 1989 -... 

Boger and co-workers have studied the intramolecular Ullmann reaction extensively. Some representative examples are shown in Table 3. For substrates in which the N10 site is not methylated, the reaction is complicated by intramolecular N-acylation of the N10—Cu amide by the C12 carbamate. In some cases, the generation of this byproduct could be suppressed by using freshly dried and degassed solvent with purified CuBr-DMS complex. 10 However, in other cases, the byproduct was still produced and the yield of the desired product suffered accordingly. 27 ... 

When two carbene functions are separated by one or more silicon atoms, one can expect them to enter independently the usual inter- or intramolecular reactions. Among the intramolecular reactions, extensions of those which have been discussed in Sections III.B and IILC are particularly appealing, namely silylcarbene-to-silene rearrangement at one or both carbene centers and intramolecular carbene dimerization to form a C,C double bond and thus an unsaturated silaheterocycle. 

Other side effects of MPH include allergic reactions, extensive bruising, and abnormally low red and white blood cells counts. Individuals who abuse the drug suffer from loss of appetite so severe that they develop anorexia. They can also suffer abdominal pain, extreme weight loss, and skin rashes. 

Cyanide addition to iminium ion, Strecker reaction Extensively used ... 

In a second area of experimentation, Leary and his associates gave the "mushroom pills to about 400 graduate students, psychologists, religious figures, mathematicians, chemists, writers, artists, musicians and other creative individuals to study their reactions. Extensive records were kept but to date only a few of these accounts have been published. 

This approach has been followed successfully for many reactions. Extensive examples have been described [9, 14, 15]. One of the most elegant illustrations is the cracking of rt-alkanes in ZSM-5 [45], where the sites can be considered to approach much better uniform energetics than in other amorphous porous catalysts. 

CO-Mb reaction, extensively studied in the last decades under a variety of experimental techniques [34,35,36,37,38,39,40], is characterized by CO diffusion within Mb leading to a heme-CO geminate pair eventually interconverting to the heme-CO covalent complex. This last step has become the most investigated biochemical process by means of computational-theoretical methods [41,42,43,44,45,46,47] and has been selected as a good test for appreciating the performances of the present methodology. 

Tautomeric equilibrium in aqueous cw-malonaldehyde, see reaction 1 in Figure 8-4, is a prototypical reaction extensively studied in the gas phase but still relatively unknown in solution. In fact, despite the large number of NMR experiments [52,53,54] and quantum chemical calculations [55] with the polarized continuum model (PCM), [1] the actual stability of czT-malonaldehyde is not well clarified, although the trans isomer should be the predominant form in water. Secondly, the involvement of the light proton in the reaction may in principle provide relevant quantum effects even in condensed phase. All these complications did not prevent this reaction to be used as a prototypical system for theoretical studies of intramolecular proton transfer in condensed phase by several investigators [56,57,58,59,60] including ourselves. 

One of the reactions extensively investigated is the heterolytic cleavage of the C(1),C(2) bond of cycloalkanones substituted in 2-position by an electron withdrawing group, Y, Scheme VII/23. 

Two types of metal-catalyzed procedures are now available for these reactions. Extensive studies have been made with heterogeneous systems which utilize a wide range of Group VIII transition metals. Recently, homogeneous metal-catalyzed systems have also been discovered.58 In this section, heterogeneous metal-catalyzed exchange only will be discussed and current homogeneous developments will be treated in the final section of this chapter. 

The most important industrial process for the production of 2-phenyl- and 2,6-diphenyl-phenol, is based on the long established self-condensations of cyclohexanone under either acidic, or preferentially basic conditions to give mono- or di-substituted aldol-like condensation products79). These easily loose water giving semicyclic or endocyclic ring double bonds. Plesec et al. have studied these reactions extensively 80). 

We have used the reaction extensively to prepare the indole moiety of several natural products. For example, the key step in the synthesis of the bacterial coenzyme methoxatin (36) is the formation of the indole (35) by intramolecular nitrene insertion from the azide (34), readily prepared from commercially available 4-aminosalicyclic acid. The third ring was annelated onto the indole (35) using conventional chemistry to give, after oxidation to the orrho-quinone, the natural product (36). 

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