Organic Syntheses by Means of Noble Metal Compounds. XIV. The Carbonylation of Cyclooctadienes

Abstract
The 1,5-cyclooctadiene - palladium chloride complex and carbon monoxide react in ethanol to form ethyl 4-cyclooctenecarboxylate. The carbonylation of 1,5-cyclooctadiene catalyzed by palladium chloride has given ethyl 4-cyclooctenecarboxylate and cyclooctanedicarboxylate. It has been found that the monoester can be obtained selectively under certain conditions; the further carbonylation of the monoester gives the diester. Under the same reaction conditions, 1,3-cyclooctadiene gives ethyl 2-cyclooctenecarboxylate in a low yield. Metallic palladium has been found to be the true catalyst and the presence of hydrogen chloride has been found to be essential for the catalysis. It has also been found that the 1, 5-cyclooctadiene - palladium chloride complex can be formed from 1,5-cyclooctadiene, metallic palladium and hydrogen chloride by heating them in an autoclave under nitrogen. It seems likely that the catalytic carbonylation of 1,5-cyclooctadiene proceeds through the formation of the 1,5-cyclooctadiene - palladium chloride complex.

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