Palladium-catalyzed synthesis of 4-cyclohexylmorpholines from reductive coupling of aryl ethers and lignin model compounds with morpholines

This work describes the highly efficient Pd-catalyzed direct coupling of aryl ethers (including the typical lignin model compounds) and morpholines to produce 4-cyclohexylmorpholines, a useful class of fine chemicals. Without employing any acidic additives, various 4-cyclohexylmorpholines could be synthesized with good yields from a variety of aryl ethers using H2 as a hydrogen resource. A mechanism study revealed that the desired product was formed via the cleavage of the C(Ar)-O bonds to generate the corresponding cyclohexanones and subsequent reductive amination.