Hydrogen chloride direct synthesis

After succeeding in the direct synthesis of allyidichlorosilane hy reacting elemental silicon with a mixture of allyl chloride and hydrogen chloride in 1993," Jung el cil. reinvestigated the Friedel-Crafts reactions of benzene derivatives with allyidichlorosilanes in detail (Eq. (2)). 

The most widely applied precursors for the synthesis of monocyclic NHPs are a-diimines which can be converted to the target heterocycles either in a two-step reaction sequence involving two-electron reduction of the diimine to an enediamide, enediamine, or a-aminoamine and subsequent condensation with PC13 [18-20] or a dichlorophosphine RPC12 [21], or via direct base-promoted reaction with PC13 [20, 22], The latter reaction involves addition of a P-Cl bond to each imine moiety followed by base-promoted elimination of hydrogen chloride leading to 2,4-dichloro-... 

The first determinations of the at. wt. of chlorine were obtained by the analysis of the chlorates later determinations have been directed towards the quantitative synthesis of hydrogen chloride, or to the use of physical methods—mol. vol., limiting densities, and critical data. General calculations have been made by F. W. Clarke, B. Brauner, and others.1... 

The above, indirect, procedure for glycoside synthesis is the Koenigs-Knorr method. Glycosidation may be effected from monosaccharides directly by treatment with an alcohol in the presence of a mineral acid catalyst. For example, when a-D-galactose (13) is heated in methanolic solution containing 2 per cent of hydrogen chloride the thermodymanically more stable methyl a-D-galacto-pyranoside (14) (Expt 5.113) is formed preferentially, and may be isolated from the reaction product by crystallisation as the monohydrate. The less abundant /i-anomer may be recovered from the mother-liquors. 

Thus, the direct synthesis of phenylchlorosilanes produces a complex mixture, which, apart from phenyltrichlorosilane, diphenyldichlorosilane, phenyldichlorosilane and triphenylchlorosilane, also contains silicon tetrachloride, trichlorosilane, benzene, solid products (diphenyl and carbon) and a gaseous product (hydrogen). It also forms high-boiling polyolefines, which are part of tank residue and can deposit on contact mass, reducing its activity. It should be kept in mind that the production of phenylchlorosilanes requires silicon with a minimal impurity of aluminum, because the aluminum chloride formed contributes to the detachment of the phenyl group from phenylchlorosilanes at higher temperature. The harmful effect of aluminum chloride is counteracted by the addition of metal salts to contact mass, which form a nonvolatile and nonreactive complex with aluminum chloride. 

Trichlorosilane can be obtained by direct synthesis from free silicon and anhydrous hydrogen chloride in the fluidised layer ... 

The synthesis of 3,4-dimethyl-D-xylose had previously been recorded10 but no direct comparison of similar derivatives of the natural and synthetic product had been made. For the synthesis, methyl 3,5-isopropyli-dene-D-xyloside (a/3 mixture) was converted into the 2-benzoate (XV) which with hot methanolic hydrogen chloride was transformed (presumably) into methyl 2-benzoyl-D-xylopyranosides (a/3 mixture) (XVI)... 

Because of the great interest in the naturally occurring nucleosides, studies of the synthesis of D-ribosides of purines and pyrimidines have been numerous. The first attempt in this direction was made by Levene and Sobotka146 who condensed the silver salt of theophylline with tri-acetyl- 8-D-ribopyranosyl bromide to obtain what was probably triacetyl-7- 8-D-ribopyranosyl theophylline (LXXVI). Subsequently Hilbert and Rist94 condensed 2,4-diethoxypyrimidine (LXXVII) with triacetyl-0-D-ribopyranosyl bromide (LXXVIII) to form ethyl bromide and 1-triacetyl-D-ribopyranosyl-4-ethoxyuracil (LXXX), which, on deacetylation with hydrogen chloride, gave 1-D-ribopyranosyluracil (LXXIX), an isomer of... 

Hydrogen chloride may be formed by direct synthesis from the elements. Although this method has been used on a commercial scale and yields a very pure product, it is not the one commonly used. It is far more convenient to treat sodium chloride with concentrated sulphuric acid. The volatile hydrogen chloride escapes from the reaction mixture and the reaction goes to completion. 

Synthesis and Polymerization of Leuchs Anhydrides. The N-carboxy-a-amino acid anhydrides, referred to as Leuchs anhydrides or as NCAs, are synthesized either from N-alkoxycarbonyl derivatives of a-amino acids or from free amino acids. Cyclization of the amino acid derivative by SOCl2 or similar reagents was described first by Leuchs in 1906, but direct synthesis involves treating the a-amino acid or its hydrochloride with phosgene as shown in Figure 4. This method, commonly termed the Fuchs-Farthing method, is the one that is used most frequently since the N-carboxyanhydride may be freed easily from the carbamyl chloride, isocyanate derivative, and hydrogen chloride by crystallization. 

Thousands of papers and patents have appeared on the direct synthesis of organochlorosilanes since 1940 when Rochow reported the direct reaction.4 These results are comprehensively accounted for in a number of earlier reviews and books.3 8 The purpose of this review is to describe the recent developing trend of the direct reaction of elemental silicon with activated or unactivated alkyl chlorides, in particular, emphasizing direct reactions with a mixture of hydrogen chloride and activated alkyl chlorides such as polychlorinated methanes, silylmethyl chlorides and dichlorides, allyl chloride, etc. 

Allylsilanes are known as interesting and useful reagents for organic synthesis.85-88 Hurd first reported the direct reaction of elemental silicon with allyl chloride in the presence of copper catalyst to give a mixture of allylchlorosilanes and polymeric materials.15 Among the volatile compounds, allyltrichlorosilane, formed by the 1 1 1 reaction of allyl chloride, hydrogen chloride and elemental silicon, was observed as the major product instead of the normally expected diallyldichlorosilane. Since diallyldichlorosilane thermally polymerizes at temperatures above 130°C, the product mixture polymerized during the reaction or upon distillation. 

Cadmium was a good promoter for the reaction, and the optimum temperature for this direct synthesis was 280 °C.24 Bis(chlorosilyl)methanes 3 and 4 were the same as those obtained in the direct reaction of silicon with a mixture of (chloromethyl)silanes 1 and hydrogen chloride,21 indicating that some of the starting (dichloromethyl)silanes 6a-d decomposed to... 

In most cases, the crude imino chloride is treated directly by adding it to a solution of stannous chloride saturated with dry hydrogen chloride the aldehyde is then liberated by steam distillation. The procedure is illustrated by the synthesis of o-tolualdehyde (70%). Imino chlorides have also been prepared by treatment of ketoximes with phosphorus penta-chloride, viz., RR C NOH — RCC1=NR, in preparations of benzalde-hyde and p-chlorobenzaldehyde (70-85%). As in the Stephen reaction (method 164), groups ortho to the imino chloride group hinder the reaction. 

Direct synthesis is the preparative method that ultimately accoimts for most of the commercial siHcon hydride production. This is the synthesis of halosilanes by the direct reaction of a halogen or haHde with siHcon metal, siHcon dioxide, siHcon carbide, or metal siHcide without an intervening chemical step or reagent. Trichlorosilane is produced by the reaction of hydrogen chloride and siHcon, ferrosiHcon, or calcium siHcide with or without a copper catalyst (82,83). Standard purity is produced in a static bed at 400—900°C. 

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