Catalytic Enantioselective Propargylic Amination-carboxylative Cyclization To Chiral 2-Oxazolidinones With CO₂ As C1 Synthon

Using CO₂ as a C1 synthon to develop asymmetric tandem reactions is one of the most effective means for CO₂ chemical fixation to synthesize high-value-added chemicals.Previously,we have reported a tandem asymmetric A³coupling-carboxylative cyclization sequence for the effective construction of chiral2-oxazolidinones.In this thesis,we further developed the first asymmetric propargylic amination-carboxylative cyclization tandem reaction for highly enantioselective synthesis of chiral 2-oxazolidinones bearing terminal alkenyl moiety.First,we designed and synthesized a series of modified pyridinebisoxazoline（PYBOX）ligands by introducing a C4 electron-donating group with large steric hindrance to enable the highly enantioselective propargylic amination.Second,it was found that the new developed chiral ligand could also facilitate the Ag-catalyzed carboxylative cyclization process.Third,the toxic effect of the Cu salts on the Ag-catalyzed cyclization could be effectively suppressed via the addition of metal chelating agents.Finally,the asymmetric propargyl amination-carboxylative cyclization tandem reaction was achieved successfully to afford a series of chiral2-oxazolidinones with terminal alkenyl moiety in 39-86%yield,71-99%ee value.The resulting chiral products could be further converted to oxazolidinone with two chiral centers or 1,3-oxazinan-2-one by hydrogenation or borohydride oxidation of the alkenyl moiety.Notably,this research represents a special waste facilitated tandem reaction.Previous studies of such kind of reactions are limited to the utilization of useful waste,while this work provides a new idea to inhibit the toxic effect of harmful waste for the development of tandem reactions.