Pyridine/alumina

Keywords aldoxime, p-toluenesulfonyl chloride, pyridine, alumina, Beckmann rearrangement, microwave irradiation, nitrile... 

AC2O, pyridine-alumina, microwave heating, no solvent, 54-100% yield. Phenols, thiols, and amines are also acylated. 

The saturator was then bypassed. The helium flow was maintained through the 300°C u-tube until the desorption of excess amine was no longer detected in the effluent. By callibrating the apparatus with the gas chromatograph it is possible to quantitate this amine/ alumina titration. For the case of pyridine, the pyridine/alumina sample was found to have 0.47% pyridine by weight. Based on a... 

Pyridine/alumina 17, 927 Pyridine borane —, reductions with — 16,113 Pyridine derivatives, 1,2,3,6-fefrahydro- 16, 855 Pyridine hydrochloride as reagent 17, 17, 793, 992 Pyridine ring (s. a. Quinoline ring)... 

Still another type of adsorption system is that in which either a proton transfer occurs between the adsorbent site and the adsorbate or a Lewis acid-base type of reaction occurs. An important group of solids having acid sites is that of the various silica-aluminas, widely used as cracking catalysts. The sites center on surface aluminum ions but could be either proton donor (Brpnsted acid) or Lewis acid in type. The type of site can be distinguished by infrared spectroscopy, since an adsorbed base, such as ammonia or pyridine, should be either in the ammonium or pyridinium ion form or in coordinated form. The type of data obtainable is illustrated in Fig. XVIII-20, which shows a portion of the infrared spectrum of pyridine adsorbed on a Mo(IV)-Al203 catalyst. In the presence of some surface water both Lewis and Brpnsted types of adsorbed pyridine are seen, as marked in the figure. Thus the features at 1450 and 1620 cm are attributed to pyridine bound to Lewis acid sites, while those at 1540... 

Tetrahydrofurfuryl alcohol reacts with ammonia to give a variety of nitrogen containing compounds depending on the conditions employed. Over a barium hydroxide-promoted skeletal nickel—aluminum catalyst, 2-tetrahydrofurfur5iarnine [4795-29-3] is produced (113—115). With paHadium on alumina catalyst in the vapor phase (250—300°C), pyridine [110-86-1] is the principal product (116—117) pyridine also is formed using Zn and Cr based catalysts (118,119). At low pressure and 200°C over a reduced nickel catalyst, piperidine is obtained in good yield (120,121). 

Reactions with Ammonia and Amines. Acetaldehyde readily adds ammonia to form acetaldehyde—ammonia. Diethyl amine [109-87-7] is obtained when acetaldehyde is added to a saturated aqueous or alcohoHc solution of ammonia and the mixture is heated to 50—75°C in the presence of a nickel catalyst and hydrogen at 1.2 MPa (12 atm). Pyridine [110-86-1] and pyridine derivatives are made from paraldehyde and aqueous ammonia in the presence of a catalyst at elevated temperatures (62) acetaldehyde may also be used but the yields of pyridine are generally lower than when paraldehyde is the starting material. The vapor-phase reaction of formaldehyde, acetaldehyde, and ammonia at 360°C over oxide catalyst was studied a 49% yield of pyridine and picolines was obtained using an activated siHca—alumina catalyst (63). Brown polymers result when acetaldehyde reacts with ammonia or amines at a pH of 6—7 and temperature of 3—25°C (64). Primary amines and acetaldehyde condense to give Schiff bases CH2CH=NR. The Schiff base reverts to the starting materials in the presence of acids. 

Reaction of formaldehyde, methanol, acetaldehyde, and ammonia over a siUca alumina catalyst at 500°C gives pyridine [110-86-1] and 3-picoline... 

The alkylation of pyridine [110-86-1] takes place through nucleophiUc or homolytic substitution because the TT-electron-deficient pyridine nucleus does not allow electrophiUc substitution, eg, Friedel-Crafts alkylation. NucleophiUc substitution, which occurs with alkah or alkaline metal compounds, and free-radical processes are not attractive for commercial appHcations. Commercially, catalytic alkylation processes via homolytic substitution of pyridine rings are important. The catalysts effective for this reaction include boron phosphate, alumina, siHca—alurnina, and Raney nickel (122). 

Astacin (P,P-carotene-3,3, 4,4 -tetraone) [514-76-1] M 592.8, m 228", 240-243"(evacuated tube), 550,000 at 498mm (pyridine). Probable impurity is astaxanthin. Purified by chromatography on alumina/fibrous clay (1 4) or sucrose, or by partition between pet ether and MeOH (alkaline). Crystd from pyridine/water. Stored in the dark under N2 at -20°. [Davis and Weedon J Chem Soc 182 I 960.]... 

Ester eliminations are normally one of two types, base catalyzed or pyrolytic. The usual choice for base catalyzed j5-elimination is a sulfonate ester, generally the tosylate or mesylate. The traditional conditions for elimination are treatment with refluxing collidine or other pyridine base, and rearrangement may occur. Alternative conditions include treatment with variously prepared aluminas, amide-metal halide-carbonate combinations, and recently, the use of DMSO either alone or in the presence of potassium -butoxide. 

First described in 1905, the Chichibabin reaction was carried out by passing vapors of aliphatic aldehyde 31 and ammonia over alumina at 300-400°C to produce the corresponding pyridine derivative 32. As a consequence, this method generates 2,3,5-trisubstiluted pyridines. 

The formation of trace amounts of 2,2 -bipyridine following reaction between pyridine and ammonia in the presence of a variety of catalysts led Wibaut and Willink to develop a method for the preparation of 2,2 -bipyridine from pyridine under the influence of a nickel-alumina catalyst. Using a pyridine-to-catalyst ratio of 10 1, temperatures between 320° and 325°C, and pressures between 42 and 44 atm, 2,2 -bipyridine was formed in yields of 0.30-0.67 gm per gram of catalyst. This method w as later applied to -picoline, to quino-line, - and to some of its derivatives, ... 

Rapoport s findings have been confirmed in the authors laboratory where the actions of carbon-supported catalysts (5% metal) derived from ruthenium, rhodium, palladium, osmium, iridium, and platinum, on pyridine, have been examined. At atmospheric pressure, at the boiling point of pyridine, and at a pyridine-to-catalyst ratio of 8 1, only palladium was active in bringing about the formation of 2,2 -bipyridine. It w as also found that different preparations of palladium-on-carbon varied widely in efficiency (yield 0.05-0.39 gm of 2,2 -bipyridine per gram of catalyst), but the factors responsible for this variation are not knowm. Palladium-on-alumina was found to be inferior to the carbon-supported preparations and gave only traces of bipyridine,... 

Reaction of -picoline with a nickel-alumina catalyst has been reported to give a mixture of four isomeric dimethylbipyridines, one of which has been identified at 6,6 -dimethyl-2,2 -bipyridine. With palladium-on-carbon, 2,4-lutidine was found to be more reactive than pyridine,and the isolated biaryl has been assigned the structure (2). However, some confusion arises from the statement that this... 

Several products other than 2,2 -biaryls have been isolated following reaction of pyridines with metal catalysts. From the reaction of a-picoline with nickel-alumina, Willink and Wibaut isolated three dimethylbipyridines in addition to the 6,6 -dimethyl-2,2 -bipyridine but their structures have not been elucidated. From the reaction of quinaldine with palladium-on-carbon, Rapoport and his co-workers " obtained a by-product which they regarded as l,2-di(2-quinolyl)-ethane. From the reactions of pyridines and quinolines with degassed Raney nickel several different types of by-product have been identified. The structures and modes of formation of these compounds are of interest as they lead to a better insight into the processes occurring when pyridines interact with metal catalysts. 

A mixture of 1.759 g of 2a.3a-epithio-5Q -endrostan-17 3-ol, 2.3 ml of 1-methoxycyclopen-tene, 20 mg of pyridine salt of p-toluenesulfonic acid and 20 ml of t-butanol is stirred for 4 hours at room temperature. The reaction mixture is poured into an aqueous solution of sodium carbonate and the whole extracted with dichloromethane. The extract is dried over anhydrous sodium sulfate and evaporated to remove solvent. Purification of the residue by chromatography over alumina gives 1.487 g of 17/3-(1-methoxycyclopentyl)oxy-2a,3a-epi-thio-50 -androstane. Yield68.2%. MP98°Cto 101°C. 

A solution of 5-methoxy-6//-l, 4-diazepine (0.386 g, 3.1 mmol) and benzoyl chloride (0.550 g, 3.9 mmol) in pyridine (5 mL) was kept for 2 d in a refrigerator and ice-water (15 mL) was then added. The mixture was extracted with CH2C12 and the extract was washed with H20. dried and concentrated under reduced pressure. The residue was chromatographed (alumina, benzene) to give the product yield 0.420 g (65%) oil. 

A mixture of 7-chloro-5-phcnyl-17/-l,4-benzodiazepin-2(3//)-one (271 g, 1.0 mol), P2S3 (242 g, 1.09 mol) and pyridine (2 L) was refluxed with stirring for 45 min. The resulting solution was cooled in an ice bath and poured slowly into ice-cold sat. brine (5 I.). The precipitated solid was collected, washed with H20, dried and dissolved in CH2C12. The solution was filtered through a bed of activated alumina and con-... 

The irradiation of 4-azido-3-methoxypyridazine (I, R = H 0.5 g, 6.6 mmol) was carried out as described above, except that only 1 cquiv of NaOMe was used. After the mixture had been evaporated the residue was dissolved in ice-cold pyridine (3 4 mL), AcCl (0.4 g, 5.1 mmol) was added, the solution was stirred at 20 C for 5-6 h then poured into ice-water (20 mL). The mixture was extracted with CH2C12 and the extract was washed successively with sat. aq NaHCOj and H20 and dried. Evaporation, followed by chromatography of the residue (alumina, 9% Et20,/CH2CI2) gave the product yield 0.34 g (26%) pale-yellow plates (hexane) mp 112-113LC. 

A mixture of PcSi(OH)2 (0.75 g, 1.3 mmol), chlorotrihexylsilane (5.0 mL), and anhyd pyridine (75 mL) was refluxed for 5 h. After the solution obtained had been allowed to cool, it was filtered and concentrated under vacuum. The resulting oil was mixed with pentane (10 mL) and the slurry formed was filtered. The solid was washed with pentane (10 mL) and acetone/H20, vacuum dried, and weighed (0.78 g). To recover additional product, the pentane filtrates were combined, concentrated, and filtered. The solid was washed and vacuum dried. The combined solids were chromatographed (alumina, toluene/hexane 1 2) yield 0.28 g (78%). 

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