2-Naphthylacetic acid thiomorpholide

Mix 130 g. of the crude thiomorpholide with 270 ml. of glacial acetic acid, 40 ml. of concentrated sulphuric acid and 60 ml. of water raise the temperature of the mixture carefully to the boiling point and reflux for 6 hours. Decant the solution from a little tarry matter into 2 litres of water and keep overnight. Collect the solid by suction filtration and wash it well with cold water. Digest the solid with a solution of 50 g. of sodium hydroxide in 1 litre of water, filter and acidify the filtrate with hydrochloric acid filter off the crude p-naphthylacetic acid, wash with water and dry. The yield of the crude acid, m.p. 137-140°, is 75 g. RecrystaUisation from benzene raises the m.p. to 142-143° the loss is about 10 per cent. 

The reaction with sulfur and morpholine can be applied to the preparation of aromatic acids containing polynuclear residues. Methyl 2-naph-thyl ketone refluxed for 16 h with a 50% excess of sulfur and morpholine furnishes a 90% yield of the thiomorpholide of 2-naphthylacetic acid, from which 2-naphthylacetic acid is obtained by refluxing for 5 h with aqueous sulfuric and acetic acid (yield 90%). 1-Acenaphthylacetic acid is prepared by heating 1-acetylacenaphthene with sulfur and ammonium sulfide at... 

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