Synthesis Of The Small-ring N-heterocyclic Silyl Ethers Catalysts For The Asymmetric Catalystic Reactions

Recently, small-ring N-heterocyclic organocatalysts have been studied widely because of their facile material, easily synthetic methods and environment-friend. How to design, synthesize small-molecule N-heterocyclic organocatalysts with high reactivity and excellent selectivity has been a research hotspot.1 The synthesis of small-ring N-heterocyclic silyl ethers catalystsStarting from (S)-methyl azetidine-2-carboxylate or (S)-methyl aziridine-2-carboxylate, a novel N-heterocyclic silyl ether catalyst was successfully prepared via a three-step route. The structures of related products were characterized by 1H NMR,13C NMR,MS,IR.2 The application in asymmetric Michael addition recationThe N-heterocyclic silyl ether catalyst was used for the asymmetric Michael addition of various aliphatic aldehydes and different nitroolefins. Influential factors were studied in detail, such as temperature, time and solvent. When 2.5 mmol aliphatic aldehydes and 0.25 mmol nitroolefins were stirred with 10 mol%(or 20 mol%) catalysts in anhydrous acetonitrile at 0℃(or 28℃) for 48 h, high enantioselectivity (98%) were achieved.3 The application in asymmetric Oxyamination recationThe N-heterocyclic silyl ether catalyst also was used for the asymmetricα-hydroxyamination recation of various aldehydes and nitrosobenzene. When aliphatic aldehydes and nitrosobenzene were stirred with 20 mol%catalysts in anhydrous dichloromethane at 0℃(or ambient temperature) for 1-2 h, high enantioselectivity (85%) were achieved.