| Chiral α-quaternary carbon structural units containing nitrogen heteroatoms are widely found in natural products,pharmaceuticals and chiral ligands.The development of catalytic asymmetric nitrogen insertion reactions is an important strategy for the synthesis of the chiral compounds.One of the key factors to success of this chiral reaction is the selection of a suitable catalytic system.In this paper,a novel catalytic model was described for the realization of intramolecular copper-nitrene-catalyzed asymmetric oxaziridination/1,2-alkyl rearrangement reactions.The oxaziridine was prepared by the new strategy,which was the addition of copper–nitrene intermediates to a carbonyl group,then the three-membered ring was opened accompanied by an alkyl C-N migration process to obtain the chiral α-quaternary carbon bicyclic lactam with high enantioselectivity.Additionally,the classical intramolecular asymmetric Schmidt reaction was failed with the result due to the intrinsic challenges:(1)the general requirement for stoichiometric amounts of a strong Lewis or Br?nsted acid;(2)the catalytic asymmetric transformation has not been achieved.This article will be elaborated from the following three chapters:Chapter 1: The catalytic asymmetric reactions of reactive intermediate species copper-nitrene,involving oxaziridination additions with double bonds and C-H aminations reaction was introduced.Chapter 2: 1,3-Cyclic diketones with alkyl azides were used as the substrates.After screening metals,ligands,solvents,additives,etc.,the optimal catalytic system was determined.Then we efficiently achieved the catalytic asymmetric oxaziridination/1,2-alkyl rearrangement reactions system under the mild conditions,producing a synthetically challenging [6,5]-and [7,5]-chiral lactams in excellent results with 34%～ 94% yields and 72% ～ 99% ee values.Finally,the reaction mechanism and intermediacy were studied in detail.Chapter 3: The chiral spiro-pyrrolidine oxazoline ligands(SPDO)based on the spiro-amino-ketone skeleton were developed by our group.The catalytic asymmetric Nazarov/Semipinacol rearrangement tandem reaction was attempted using the ligands. |
