Direct Reductive Amination of Aldehydes Using Hantzsch Ester Promoted by N,N'-Diphenyl-S-Benzylisothiouronium Iodide as an Organocatalyst

摘要

The direct reductive amination of aldehydes is an extremely useful synthetic method to prepare carbon-nitrogen bonds and introduce a wide variety of different alkyl groups onto an amine moiety.1 This reaction involves the one-pot transformation of an amine into its corresponding inline followed by its reduction without needing to separate the imine intermediate.This is a much more controlled way of forming carbon-nitrogen bonds.The selection of a suitable reducing agent is needed,which is capable to facilitate formation of the imine and selectively reduce the C=N group in the presence of the aldehyde starting material.Hantzsch ester,an organic hydride donor,has been widely employed in biomimetic methods as a potent reducing agent.Hantzsch ester is generally a more efficient reducing agent for imines in the presence of a catalyst such as thiourea,scandium triflate Sc(OTf)3'4 disulfonimide,5 binol phosphoric acid,and B(C6F5)3.