Selectivity control in one-pot myrtenol amination over Au/ZrO2 by molecular hydrogen addition

•H2 addition enhances selectivity to target amines in one-pot amination over Au/ZrO2.•H2 insertion at 100 °C provides selective CN saturation without hydrogenating CC bond.•H2 addition at 180 °C provokes saturation of both CC and CN bonds.•Higher trans-amine selectivity after H2 addition at 180 °C at full myrtenol conversion.

The one-pot myrtenol amination was studied over Au (3 wt.%)/ZrO2 catalyst under mixed N2/H2 atmosphere (9 bar). The effect of hydrogen addition was explored with the aim to increase selectivity to the target amines. Hydrogen addition timing depending on myrtenol conversion and hydrogenation temperature affected selectivity to the reaction products. Hydrogen addition (1 bar) after almost complete myrtenol conversion at 100 °C increased the yield to amine up to 68% preserving CC bond in the initial myrtenol structure. Hydrogen addition at 180 °C irrespective of the myrtenol conversion level provoked reduction of both CC and CN bonds with formation of two diastereomers (yield up to 93%), with trans-isomer formation being preferred when hydrogen was added at almost complete myrtenol conversion. It was shown, that in the presence of a gold catalyst controlled hydrogenation of competitive CC and CN groups can be performed during one-pot alcohol amination by regulation of the reaction conditions.

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