Xylenes reduction

Iridium and rhodium nanoparticles have also been studied in the hydrogenation of various aromatic compoimds. In all cases, total conversions were not observed in BMI PF6. TOFs based on mol of cyclohexane formed were 44 h for toluene hydrogenation with Ir (0) and 24 h and 5 h for p-xylene reduction with lr(0) or Rh(0) nanoparticles, respectively. The cis-1,4-dimethylcyclohexane is the major product and the cisitrans ratio depends on the nature of the metal 5 1 for lr(0) and 2 1 for Rh(0). TEM experiments show a mean diameter of 2.3 nm and 2.1 nm for rhodium and iridium particles, respectively. The same nanoparticle size distribution is observed after catalysis (Fig. 4). 

The procedure is to pass purified hydrogen through a hot solution of the pure acid chloride in toluene or xylene in the presence of the catalyst the exit gases are bubbled through water to absorb the hydrogen chloride, and the solution is titrated with standard alkali from time to time so that the reduction may be stopped when the theoretical quantity of hydrogen chloride has been evolved. Further reduction would lead to the corresponding alcohol and hydrocarbon ... 

The stock solution of quinoline-sulphur poison is prepared by refluxing I g. of sulphur with 6 g. of quinoline for 5 hours and diluting the resulting brown liquid to 70 nJ. with xylene which has been purified by distilling over anhydrous aluminium chloride. The addition of the quinoline - sulphur poison ensures that the reduction does not proceed beyond the aldehyde stage it merely slows up the reaction and has no harmful effects. 

The catalyst commonly used in this method is 5 wt % palladium supported on barium sulfate inhibited with quinoline—sulfur, thiourea, or thiophene to prevent reduction of the product aldehyde. A procedure is found in the Hterature (57). Suitable solvents are toluene, benzene, and xylene used under reflux conditions. Interestingly, it is now thought that Rosenmund s method (59) originally was successful because of the presence of sulfur compounds in the xylene used, since the need for an inhibitor to reduce catalyst activity was not described until three years later (60). 

A thiol can be protected by oxidation (with O2 H2O2 I2. - ) to the corresponding symmetrical disulfide, which subsequently can be cleaved by reduction [Sn/HCl Na/xylene, Et20, or NH3 LiAlH4 NaBH4 or thiols such as HO(CH2)2SH]. Un-symmetrical disulfides have also been prepared and are discussed. 

Butyroin has been prepared by reductive condensation of ethyl butyrate with sodium in xylene, or with sodium in the presence of chloro-trimethylsilane. and by reduction of 4,5-octanedlone with sodium l-benzyl-3-carbamoyl-l,4-dihydropyridine-4-sulfinate in the presence of magnesium chloride or with thiophenol in the presence of iron polyphthalocyanine as electron transfer agent.This acyloin has also been obtained by oxidation of (E)-4-octene with potassium permanganate and by reaction of... 

The synthesis of meconin has been referred to already (p. 201). Cotarnine has been synthesised by Salway from myristicin (I) as a starting-point. This was transformed into jS-3-methoxy-4 5-methylenedioxy-phenylpropionic acid (II), the amide of which was converted by Hofmann s reaction into )S-3-methoxy-4 5-methylenedioxyphenylethylamine, and the phenylacetyl derivative (HI) of this condensed, by heating it in xylene solution with phosphoric oxide, giving rise to the two possible dihydroiso-quinoline derivatives. The first of these substances, 8-methoxy-6 7-methylenedipxy-1-benzyl-3 4-dihydroiioquinoline (IV), on conversion into the methochloride and reduction with tin and hydrochloric acid, gave... 

Both sodium acetylide in xylene (Air Reduction Corporation) and lithium acetylide-ethylenediamine complex (Foote Mineral Co.) are now commercially available, and have been used successfully for the ethynylation of 17-keto steroids. 

The procedure described is a modification of the general procedure of Angyal2 for the preparation of aldehydes from benzylamines by the Sommelet reaction. Isophthalaldehyde has been prepared from w-xylene by preparation of the tetrachloro derivative and hydrolysis,3 from isophthaloyl chloride by the Rosenmund reaction,4 from a,a -dibromo-m-xylene by the Sommelet reaction,5 and from isophthaloyl chloride by reduction with lithium tri-Cbutoxyaluminumhydride.6... 

Besides simple alkyl-substituted sulfoxides, (a-chloroalkyl)sulfoxides have been used as reagents for diastereoselective addition reactions. Thus, a synthesis of enantiomerically pure 2-hydroxy carboxylates is based on the addition of (-)-l-[(l-chlorobutyl)sulfinyl]-4-methyl-benzene (10) to aldehydes433. The sulfoxide, optically pure with respect to the sulfoxide chirality but a mixture of diastereomers with respect to the a-sulfinyl carbon, can be readily deprotonated at — 55 °C. Subsequent addition to aldehydes afforded a mixture of the diastereomers 11A and 11B. Although the diastereoselectivity of the addition reaction is very low, the diastereomers are easily separated by flash chromatography. Thermal elimination of the sulfinyl group in refluxing xylene cleanly afforded the vinyl chlorides 12 A/12B in high chemical yield as a mixture of E- and Z-isomers. After ozonolysis in ethanol, followed by reductive workup, enantiomerically pure ethyl a-hydroxycarboxylates were obtained. 

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