Sulfur-refluxed quinoline

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). 

Rosenmund reaction. The quinoline-sulfur poison of Rosenmund and Zetzsche is prepared by refluxing 1 g. of sulfur with 6 g. of quinoline for 5 hrs. and diluting the resultant dark brown solution with purified xylene to 70 ml. In reducing 8-naphthoyl chloride to /3-naphthaldehyde, Hershberg and Cason passed hydrogen... 

Effect of Addition of Sulfur-Refluxed Quinoline Poison added Percentage yield of benzaldehyde... 

Elimination of sulfur from methyl dibenzo[/),/]thiepin-10-carboxylatcs 15 (R2 = Me) can be achieved in moderate yields (39-55%) upon refluxing in diethyl phthalate in the presence of copper bronze.60 For the dibenzo[A,/]thiepin-10-carboxylic acids 15 (R2 = H), the loss of sulfur is accompanied by decarboxylation. Thus, treatment of these acids with copper bronze in refluxing quinoline for four hours gives the corresponding phenanthrenes 16 (R3 = H) in moderate yield (50%). However, the exposure time to high temperatures influences the product formation. Thus, the decarboxyiated dibenzothiepins are obtained after refluxing for only five minutes.60... 

One hundred grams of concentrated sulfuric acid is added to a mixture of 100 g. of arsenic acid, 100 g. (0.70 mole) of /8-naphthylamine, and 215 g. of glycerol heated to 140°. After the initially formed solid has dissolved, another 100 g. of sulfuric acid is added dropwise, the mixture is refluxed at 150-155° for 4 hours, poured into 2 1. water, allowed to stand overnight, and filtered, and the filtrate is carefully neutralized by the dropwise addition with vigorous stirring of 6 N sodium hydroxide solution. The precipitated solid is removed by filtration, dried, and dissolved in acetone, and the hydrochloride is precipitated by the addition of dry hydrogen chloride to the acetone solution. The precipitated salt is dissolved in water, treated with activated carbon, and reprecipitated with 6 N sodium hydroxide to give 102 g. (81.5%) of benzo[/]quinoline, m.p. 93° after recrystallization from water-ethanol. 

Quinoline S is prepared by heating 1 g of sulfur and 6 g of quinoline for 6 h under a reflux condenser and diluting the product with 70 ml of xylene that has been freed from poisons. 

A few drops of coned, sulfuric acid added to a mixture of ethyl acetoacetate and triethyl orthoformate, stored 24 hrs., and neutralized with a slight excess of quinoline ethyl j -ethoxy-cis-crotonate (Y 89%) dissolved in dry ether, added to a suspension of 2 moles LiNHg in anhydrous liq. NHg, stirring continued 10 min., a soln. of benzaldehyde in dry ether added, stirred 1 hr., NHg replaced by ether, refluxed 5 min., and ice-water added 3-ethoxy-5-phenyl-cis-2-frans-4-pentadienoic acid (Y 74%). — Excess LiNHg is used to prevent self-condensation of the ester. F. e. s. E. E. Smissman and A. N. Voldeng, J. Org. Ghem. 29, 3161 (1964). 

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