Quinoline catalyst

Pyrrole-2-carboxylic acid easily loses the carboxylic group thermally. Pyrrole-3-carboxylic acid and furan-2- and -3-carboxylic acids also readily decarboxylate on heating to about 200°C. Thiophene-carboxylic acids require higher temperatures or a copper-quinoline catalyst. In furans, 2-carboxylic acid groups are lost more readily than 3-carboxylic acid groups (Scheme 64). 

Quinoline Catalyst" Temperature (°C) Time (h)rf Product Ratio (%) 1,2,3,4- 5,6,7,8-Tetrahydro Tetrahydro ... 

The use of a variety of chiral catalysts for the asymmetric epoxidation of ot,p-unsaturated ketones has produced some interesting results. The use of a bis-quinoline catalyst, 24, and HPj as oxidant provides the desired epoxide 19 <05AG(I)1383>. 

These compounds can be malodorous as in the case of quinoline, or they can have a plecisant odor as does indole. They decompose on heating to give organic bases or ammonia that reduce the acidity of refining catalysts in conversion units such as reformers or crackers, and initiate gum formation in distillates (kerosene, gas oil). 

Lindlar Catalyst ( Pd/BaS04/ quinoline)- partially poisoned to reduce activity will only reduce the most reactive functional groups. 

The 7V-methylbenzo[( e]quinoline 426 was prepared by trapping the insertion product of an internal alkyne with a tertiary dimethylamine. One methyl group is eliminated. The dimethylaminonaphthalene-Pd complex 427 is an active catalyst and other Pd compounds are inactive[290a]. 

Both objectives have been met by designing special hydrogenation catalysts The most frequently used one is the Lindlar catalyst, a palladium on calcium carbonate combi nation to which lead acetate and quinoline have been added Lead acetate and quinoline partially deactivate ( poison ) the catalyst making it a poor catalyst for alkene hydro genation while retaining its ability to catalyze the addition of H2 to the triple bond... 

The structure of quinoline is shown on page 460 In sub sequent equations we will simply use the term Lindlar Pd to stand for all of the components of the Lindlar catalyst... 

The oxidative dehydration of isobutyric acid [79-31-2] to methacrylic acid is most often carried out over iron—phosphoms or molybdenum—phosphoms based catalysts similar to those used in the oxidation of methacrolein to methacrylic acid. Conversions in excess of 95% and selectivity to methacrylic acid of 75—85% have been attained, resulting in single-pass yields of nearly 80%. The use of cesium-, copper-, and vanadium-doped catalysts are reported to be beneficial (96), as is the use of cesium in conjunction with quinoline (97). Generally the iron—phosphoms catalysts require temperatures in the vicinity of 400°C, in contrast to the molybdenum-based catalysts that exhibit comparable reactivity at 300°C (98). 

In this process, catalysts, such as boric acid, molybdenum oxide, zirconium, and titanium tetrachloride or ammonium molybdate, are used to accelerate the reaction. The synthesis is either carried out in a solvent (aUphatic hydrocarbon, trichlorobenzene, quinoline, pyridine, glycols, or alcohols) at approximately 200°C or without a solvent at 300°C (51,52). 

Ca.ta.lysts, A small amount of quinoline promotes the formation of rigid foams (qv) from diols and unsaturated dicarboxyhc acids (100). Acrolein and methacrolein 1,4-addition polymerisation is catalysed by lithium complexes of quinoline (101). Organic bases, including quinoline, promote the dehydrogenation of unbranched alkanes to unbranched alkenes using platinum on sodium mordenite (102). The peracetic acid epoxidation of a wide range of alkenes is catalysed by 8-hydroxyquinoline (103). Hydroformylation catalysts have been improved using 2-quinolone [59-31-4] (104) (see Catalysis). 

Uses. Isoquinoline and isoquinoline derivatives are usehil as corrosion inhibitors, antioxidants, pesticides, and catalysts. They are used in plating baths and misceUaneous appHcations, such as in photography, polymers, and azo dyes (qv). Numerous derivatives have been prepared and evaluated as pharmaceuticals. Isoquinoline is a main component in quinoline stiH residue bases, which are sold as corrosion inhibitors and acid inhibitors for pickling iron and steel. 

Phenols. Phenols are unreactive toward chloroformates at room temperature and at elevated temperatures the yields of carbonates are relatively poor (< 10%) in the absence of catalysis. Many catalysts have been claimed in the patent Hterature that lead to high yields of carbonates from phenol and chloroformates. The use of catalyst is even more essential in the reaction of phenols and aryl chloroformates. Among the catalysts claimed are amphoteric metals or thek haUdes (16), magnesium haUdes (17), magnesium or manganese (18), secondary or tertiary amines such as imidazole (19), pyridine, quinoline, picoline (20—22), heterocycHc basic compounds (23) and carbonamides, thiocarbonamides, phosphoroamides, and sulfonamides (24). 

The presence of other functional groups ia an acetylenic molecule frequendy does not affect partial hydrogenation because many groups such as olefins are less strongly adsorbed on the catalytic site. Supported palladium catalysts deactivated with lead (such as the Liadlar catalyst), sulfur, or quinoline have been used for hydrogenation of acetylenic compound to (predominantiy) cis-olefins. 

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). 

Practically all pyridazine-carboxylic and -polycarboxylic acids undergo decarboxylation when heated above 200 °C. As the corresponding products are usually isolated in high yields, decarboxylation is frequently used as the best synthetic route for many pyridazine and pyridazinone derivatives. For example, pyridazine-3-carboxylic acid eliminates carbon dioxide when heated at reduced pressure to give pyridazine in almost quantitative yield, but pyridazine is obtained in poor yield from pyridazine-4-carboxylic acid. Decarboxylation is usually carried out in acid solution, or by heating dry silver salts, while organic bases such as aniline, dimethylaniline and quinoline are used as catalysts for monodecarboxylation of pyridazine-4,5-dicarboxylic acids. 

Lindlar catalyst (Section 9.9) A catalyst for the hydrogenation of alkynes to cA-alkenes. It is composed of palladium, which has been poisoned with lead(II) acetate and quinoline, supported on calcium carbonate. 

A series of 2-aryloxazolo[4,5-/i]quinoline-5-arylidines was prepared by the reaction of 5,7-diamino-8-hydroxyquinoline with aromatic or aliphatic aldehydes in the presence of a basic catalyst such as piperidine. On the other hand, 2-styryl-5-diacetylamino-oxazolo[4,5-/i]quinolines were prepared by interaction of 2-methyl-5-diacetylamino-oxazolo[4,5-/i]quinoline with aromatic aldehydes (77MI1, 82MI2) (Scheme 6). 

In 1960 Rapoport and his co-workers found that some 2,2 -biquinoline is formed when quinoline w as used as a solvent for dehydrogenations in the presence of palladiuin-on-carbon catalyst, and they showed that several related bases (including pyridine) gave 2,2 -biai yls when refluxed at atmospheric pressure with a 5% pal-ladium-on-carbon catalyst. With a pyridine-to-catalyst ratio of 10 1, 11% conversion of pyridine to 2,2 -bipyridine was observed after heating for 24 hr. 

---