The first enantioselective aza-Darzens reaction of cyclic imines with a-halogenated ketones was realized under mild reaction conditions by using amino-acid-derived bifunctional phosphonium salts as phase-transfer promoters.A variety of structurally dense tri-and tetrasubstituted aziridine derivatives,c ontaining benzofused heterocycles as well as spiro-structures,w ere readily synthesized in high yields with excellent diastereo-and enantioselectivities (up to > 20:1 d.r. and > 99.9 %ee). The highly functionalizedaziridine products could be easily transformed into different classes of biologically active compounds.Optically pure fused N-heterocycles,e specially aziridinecontaining molecules,are versatile intermediates in chemical synthesis, [1] and they are also prevalent building blocks in many biologically active compounds,i ncluding natural alkaloids and pharmaceutical agents (Scheme 1). [2] Accordingly, an umber of catalytic methods have been devised for the stereoselective construction of such structural motifs over the past two decades. [3][4][5][6][7][8][9] In this context, the aza-Darzens reaction becomes one of the most straightforward and efficient approaches for producing such ring systems. [5] Lewis and Brønsted acid catalyzed aza-Darzens of a-diazoacetates and imines,offering aziridines,were first disclosed by Brookhart, Te mpleton, and co-worker. [6] Thea symmetric variants of these acid-catalyzed aza-Darzens reactions were first reported by Wulff and co-workers [7] and further developed by Maruoka and co-workers, [8] and others, [9] particularly providing cis-o r/and trans-disubstituted aziridines in high yields with excellent stereoselectivities.However,less success has been achieved in direct construction of trisubstituted chiral aziridine scaffolds by this process,a nd only two examples were reported. [10] Maruoka and co-workers dis-closed achiral Brønsted acid catalyzed aziridination between N-a-diazoacylo xazolidinones and N-Boc imines,t hus creating trisubstituted chiral aziridine skeletons. [10a] Quite recently, Tr ost developed aZ n-ProPhenol catalyzed aza-Darzens reaction of chlorinated aromatic ketones with N-Boc aldimines,p roviding an ovel method for constructing trisubstituted chiral aziridine motifs. [10b] Although these impressive advances have been made,h ighly enantioselective preparation of trisubstituted aziridine rings is still synthetically challenging,let alone direct asymmetric synthesis of structurally dense tetrasubstituted chiral aziridine molecules.T ot he best of our knowledge,n og eneral and straightforward catalytic protocol to access optically pure tetrasubstituted aziridines has been reported so far. Therefore,i ti sh ighly desirable to explore autilitarian strategy to fill this void.In this study,w ea ttempted to develop an alternative approach to prepare structurally dense tri-and tetrasubstituted aziridines with readily available catalysts and reagents. In the past decades,a symmetric phase-transfer catalysis (PTC) has been recognized as ap owerful and versatile...

Humanity has an urgent need to develop more degradable materials for solving environmental pollution. In this study, through host-guest interactions between fatty acids-modified b-cyclodextrin (Em-bCD) and polyethylenimine (PEI) oligomer-grafted ferrocene (PEI-Fc), we designed and prepared a supramolecular polymer (PEI-Fc/Em-bCD complex), which showed polymeric properties and was able to be used as a cushioning material due to its good compressibility. Compared with conventional polymers, a remarkable advantage of the PEI-Fc/Em-bCD complex is that it can be dismantled into small molecules and rebuilt easily by controlling the dissociation or reformation of bCD-Fc inclusion complexes.Furthermore, the material also exhibited good self-healing properties.

In this paper, we fabricated a magnetically driven walking device comprising magnetically active layer-by-layer films. By alternating the magnetic fields, the device walked steadily and fast on the substrate like an inchworm, and showed good transportation capability.