Ring Opening Reaction Of Amines And Aziridines Under Green Reaction Conditions

The occurrence of a vicinal diamine motif is quite common in natural and artificial organic compounds exhibiting catalytic,biological and pharmacological properties.Enantioenriched vicinal diamine catalysts or ligands have found extensive application in asymmetric catalysis,such as asymmetric（transfer）hydrogenation,and Michael,Mannich and aldol reactions.Thus the exploration of a highly efficient and selective synthetic methodology to synthesize such types of molecules in a racemic or chiral form remains extremely desirable,especially in a green manner.Among the already established protocols,the ring opening reaction of nitrogen nucleophiles and aziridines–featuring a three-membered strained ring–represents an important way to access vicinal diamines.（1）According to the survey of related studies,acidic（LUMO-lowering strategy）or basic catalysis（HOMO-raising strategy）under solvent media conditions was usually taken up in such types of transformation.In some cases,a large excess of nitrogen nucleophiles was used to accelerate and complete the reactions.Environmental concerns prompted us to seek more user-friendly and atom-economical conditions of the existing protocols.The aza-addition of aziridines to obtain vicinal-diamines was achieved under catalyst-and solvent-free conditions for the first time.Various aryl,alkyl and meso-bicyclic aziridines with a Ts-protecting group were tolerated,and aromatic amine-nucleophiles containing electron withdrawing and donating groups in the phenyl ring were applied.The plausible reaction mechanism involving hydrogen bonding and proton transfer was proposed.Thesyntheticutilityofoneadditionadducttothe4-amino-1,2,3,4-tetrahydroisoquinoline derivative through the Pictet–Spengler reaction was realized.All new compounds have been characterized by ¹H and ¹³C NMR and HRMS.（2）By means of asymmetric catalysis,the reaction of N-Ts protected phenyl aziridine and aniline generated chiral vicinal-diamine compounds in the presence of chiral Ag（I）complexes.After screening various solvents and chiral ligands,up to72%yield and 59%ee（enantiomeric excess）were obtained.Furthermore,four other kinds of aziridine with different N-protective groups were also studied.Further investigation were required to improve the catalytic results.