Direct Reductive Amination of Carbonyl Compounds with H2 Using Heterogeneous Catalysts in Continuous Flow as an Alternative to N-Alkylation with Alkyl Halides

A general continuous-flow procedure for direct reductive amination of secondary and primary amines with aromatic and aliphatic aldehydes as well as ketones is reported. The use of hydrogen gas and commercially available Pt/C as a heterogeneous catalyst is a key. In addition to exhibiting an excellent functional group tolerance, this method allows the fast formation of C-N bonds without production of any hazardous chemical waste. Applications to the synthesis of key intermediates toward active pharmaceutical ingredients (Donepezil and Arformoterol/Tamsulosin) are also described.