Ring-Opening Reactions Enabled By Organic Base/Metal Combined Catalysis

The organobase/metal combined catalysis has been widely used in asymmetric synthesis and polymer synthesis.In the realm of asymmetric synthesis,a variety of combinations of chiral Lewis bases and metals have been developed,which have enabled efficiently achieved numerous transformations that are inaccessible by traditional single-component catalysis.The Lewis base/metallic Lewis acid combined catalysis also expands homo-and copolymerizations of a tremendous number of monomers to new domains.Such a combined catalytic strategy can substantially improve the performance of polymerizations toward not only high molecular weight and low dispersity,but also sequence-control.As such,further endeavors to design novel and robust organobase/metal combined catalytic systems are of great importance and highly desirable.In this dissertation,several organobase/metal-catalyzed ringopening reactions of aziridines and cyclopropanes were investigated.First,we have established an efficient synthesis of highly enantioenriched 1,4benzodiazepinones and 1,4-benzoxazepinones by chiral N-Heterocyclic carbene and iridium combined-catalyzed formal[4+3]annulation reaction.The chiral NHeterocyclic carbene catalyst serves not only as a chiral ligand of the iridium to tune the catalytic performance but also as an organocatalyst of the asymmetric oxidative lactamization event.The achiral urea additive also works cooperatively with an iridium catalyst to facilitate the control of stereoselectivity.The utility of this methodology has been demonstrated in the context of catalytic asymmetric synthesis of a selective inhibitor of mitochondrial F1F0 ATP hydrolase.Second,we developed an unprecedented regeoselective ring-opening polymerization of vinyl aziridines via phosphazene/iridium combined catalysis,affording polysulfonamide with narrow molecular weight distribution.More importantly,optically active chiral polymers were successfully synthesized by using chiral phosphoramidite ligands.Last,a highly efficient organobase/Lewis acid cooperative catalytic system was discovered for ring-opening polymerization of donor-acceptor cyclopropanes.The Br?nsted base/Lewis acid catalytic system is the essence of two key processes:cooperative activation towards chain-end hydrogens and free monomers drives C(sp3)H alkylation propagation;DBU-mediated reversible chain-end deprotonation/protonation process that secures the controlled and living characteristics.Topological poly(cyclopropanes)were therefore accessed by manipulation of polymerization conditions and structural modification of monomers.