Temperature large-scale synthesis

Among the 1,2,4-triazolides benzenesulfonyl-, p-toluenesulfonyl-, mesitylenesulfonyl-, triisopropylsulfonyl-, and p-nitrobenzenesulfonyltriazole (IV), the latter is the most reactive one (room temperature, 24 h, pyridine). 1151 341 1261 It was therefore also used for large-scale synthesis of fully protected di-, tri-, and hexadeoxyribonucleotides of defined sequence. 341 1161... 

In most oases, the fluoro Pummerer reaction can be carried out with 1.33 to 2.0 equiv of DAST and a "catalytic" amount of antimony trichloride in either refluxing methylene chloride or chloroform at room temperature or 50°C. In the synthesis of fluoromethyl phenyl sulfide, however, the induction period makes room temperature conditions the preferred method for large scale synthesis. 

The particle diameter and pore size of the silica gel materials depend on the concentration of silicic acid, the pH, the solvent and mixing conditions, and the reaction temperature. Technical skill is necessary for reproducible large-scale synthesis. 

For the stoichiometric liquid-liquid large-scale synthesis a flat steel pan (31x44 cm ) was charged with benzaldehyde (77k) (99.5% 848 g, 7.95 mol) and aniline (236s) (99.5% 744 g, 7.95 mol) (Scheme 51). The liquids were mixed at 18 °C. The temperature rose to a maximum of 32 °C and fell back to 24 °C when crystallization started with another increase in temperature to a maximum of 35 °C within 12 min when crystallization was virtually complete and water of reaction separated. Next day, the wet crystal cake was crunched with an ordinary household grain mill and dried in a vacuum at room temperature to give 1.438 kg (100%) of pure benzylidene-aniline (54s). 

The characteristic pyrolytic process for acid chlorides is loss of HC1 and this occurs for the bicyclic example 235 on FVP at 800 °C to give cyclohexa-1,2-diene 238 by way of the ketene 236 and carbene 237 as shown113. The product can be directly observed by low-temperature IR and forms a [2 + 2] dimer on warming up. FVP of >-toluoyl chloride 239 at 630 °C also results in loss of HC1 to provide a dependable large-scale synthesis of benzocyclobutenone 240 in excellent yield114. Pyrolysis of trichloroacetyl chloride, CI3C—COC1, over a bed of zinc at 420 °C results in dechlorination... 

The first breakthrough in the large-scale synthesis of ammonia resulted from the development of the Haber process in 1913 in which ammonia was produced by the direct combination of two elements, nitrogen and hydrogen, in the presence of a catalyst (iron oxide with small quantities of cerium and chromium) at a relatively high temperature (550°C) and under a pressure of about 2940 psi (20.3 MPa). 

With conventional protocols requiring low reaction temperatures, typically —78 °C, to prevent side reactions from occurring, scaling the reaction for industrial production of such compounds has proved difficult. As such, the authors evaluated the process under continuous flow, proposing that the effective temperature control and accurate residence times attainable within miniaturized flow reactors would enable the synthesis of diarylethenes at temperatures above — 78 °C and thus facilitate the large-scale synthesis of such compounds. 

A large-scale synthesis of dialkyl 3-oxoaIkylphosphonates proceeds by treatment of dialkyl 1-copper(l)alkylphosphonates with 2,3-dihalopropenes. Low-temperature hydrolysis of the resulting vinyl halide with H2SO4 in biphasic medium releases the y-keto functionality (Scheme 7.56). Thus, alkylation of l-copper(I)alkylphosphonates with 1,2-dichloro- or l,2-dibromo-2-propene is equivalent to the introduction of masked 3- or 4-oxoalkyl groups. In this way, 1-substituted or unsubstituted 3-oxoalkylphosphonates are prepared in high yields (90%). ... 

Low surface area carbon nanotubes can be efficiently used as a catalyst support for the large scale synthesis of carbon nanofibers under relatively mild synthetic conditions, i.e. < 650 °C. The material obtained has a relatively high surface area (100-250 m /g depending on the synthesis temperature) with a mesoporous distribution. Both high carbon... 

It has been found that nonstabilized ylides derived from the tetrahydro-phosphole nucleus (90 or 91) afford oxaphosphetanes that decompose at room temperature. Sin( 89, the phosphonium salt precursor of 90, contains only one alkyl group, BTP ylide 90 can be recommended for E-selective alkene synthesis in cases where the alkyl substituent must be used efficiently. Since the phosphorus environment in 90 is relatively expensive, this family of reagents will not provide a practical solution for large-scale synthesis of... 

In a study of the synthesis of thymidine-3-phosphoramidites of various amines and their use in the synthesis of fully protected thymidine dimers, a series of monoazacycloalkanes was tested as the amine component <84TL5513>. It was shown that the condensations in solution work especially well with yields exceeding 90% when p-nitrophenylethyl phosphoramidites of hexahydroazepine, octahydroazonine, and azacyclotridecane were used. These compounds can easily be purified and stored at room temperature, so that they might be useful synthons for large-scale synthesis of oligodeoxyribonucleotides, where a low excess of phosphoramidites is desirable. 

Reduction Reaction. DIBAL has been shown to be a practical reagent to reduce secondary phosphine oxides (eq 36). In most cases, this reaction is carried out in hydrocarbon solvent at room temperature and was demonstrated to be a convenient large scale synthesis. 

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