Enantioselective Bromocyclization of Olefins Catalyzed by Chiral Phosphoric Acid

A chiral phosphoric acid catalyzed enantioselective bromocyclization of olefins is described. Various <i>cis</i>-, <i>trans</i>-, or trisubstituted γ-hydroxy-alkenes and γ-amino-alkenes can cyclize under the reaction conditions to give optically active 2-substituted tetrahydrofurans and tetrahydropyrroles in up to 91% ee

Enantioselective Bromocyclization of Olefins Catalyzed by Chiral Phosphoric Acid

A chiral phosphoric acid catalyzed enantioselective bromocyclization of olefins is described. Various <i>cis</i>-, <i>trans</i>-, or trisubstituted γ-hydroxy-alkenes and γ-amino-alkenes can cyclize under the reaction conditions to give optically active 2-substituted tetrahydrofurans and tetrahydropyrroles in up to 91% ee

Enantioselective Bromocyclization of Olefins Catalyzed by Chiral Phosphoric Acid

A chiral phosphoric acid catalyzed enantioselective bromocyclization of olefins is described. Various <i>cis</i>-, <i>trans</i>-, or trisubstituted γ-hydroxy-alkenes and γ-amino-alkenes can cyclize under the reaction conditions to give optically active 2-substituted tetrahydrofurans and tetrahydropyrroles in up to 91% ee

Tunable High-Performance Electromagnetic Interference Shielding of VO₂ Nanowires-Based Composite

The unique metal–insulator transition of VO2 is very suitable for dynamic electromagnetic (EM) regulation materials due to its sharp change in electrical conductivity. Here, we have developed an off/on switchable electromagnetic interference (EMI) shielding composite by interconnecting VO2 nanowires (NWs) in poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) to form conductive networks, resulting in outstanding performance at the X and Ku bands with maximum change values of 44.8 and 59.4 dB, respectively. The unique insulator-to-metal transition (IMT) of VO2 NWs has dominated the variation of polarization loss (εp″) and conductivity loss (εσ″) for the composites, which is the mechanism of EMI shielding switching between off and on states. Furthermore, the composite exhibits good cycling stability of the off/on switchable EMI shielding performance and has excellent mechanical properties, especially with 200 times abrasion resistance without obvious weight loss. This study provides a unique approach for dynamic switching of EM response with the potential to construct practical intelligent EM response systems for next-generation smart electromagnetic devices in various scenarios