HOMOGENEOUS HYDROGENATION OF DIOLEFINS CATALYZED BY TRICARBONYL CHROMIUM COMPLEXES .2. DEUTERATION

Deuterium tracer studies provide direct evidence that 1,4 addition is the dominant mechanism of reduction catalyzed by arene-Cr(CO)3. Catalytic deuteration of dienes yields almost exclusively monoenes-d2 with deuterium located on the α-methylenes. Hydrogen and deuterium addition are predominantly molecular. Although no deuterium is exchanged with hydrogen in conjugated dienes, this exchange occurs at the α-methylenes in methyl linoleate and oleate and is apparently stereoselectively cis. With monoenes, positional and geometric isomerization by a 1,3-hydrogen shift is indicated. Key intermediates postulated include D2Cr(CO)3 and diene-D2Cr(CO)3 for 1,4 addition, cis monoolefin-Cr(CO)3 for deuterium exchange, and π-allyl-CrH(CO)3 for isomerization reactions. © 1969, American Chemical Society. All rights reserved.