Novel Palladium‐Catalysed Hydroamination of Myrcene and Catalyst Separation by Thermomorphic Solvent Systems

Abstract

AbstractHydroamination is an elegant and atom economical reaction to convert alkenes into amines. One of the few technical realisations of this reaction is the hydroamination of myrcene to diethylgeranylamine, an important precursor of (−)‐menthol. However, this so‐called “Takasago process” is catalysed by high amounts of alkali metals, especially lithium, which makes it a relatively expensive approach. In the present work, the hydroamination of myrcene with morpholine is catalysed by palladium complexes with bidentate ligands such as bis(diphenylphosphino)butane (DPPB) or bis(2‐diphenylphosphinophenyl) ether (DPEphos). The systematic optimisation of the reaction parameters under single‐phase conditions led to yields of the 1,4‐adducts of higher than 90%. The only side products proved to be the telomers of myrcene, whose formation could be decreased by using appropriate reaction conditions. The method of temperature‐dependent solvent systems was successfully applied to separate the palladium catalyst from the amines with a palladium leaching lower than 1.0%.