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This paper describes a catalytic asymmetric Staudinger-aza-Wittig reaction of (o-azidoaryl)malonates, allowing access to chiral quaternary oxindoles through phosphine oxide catalysis. We designed a novel HypPhos oxide catalyst to enable the desymmetrizing Staudinger-aza-Wittig reaction through the PIII/PV═O redox cycle in the presence of a silane reductant and an IrI-based Lewis acid. The reaction occurs under mild conditions, with good functional group tolerance, a wide substrate scope, and excellent enantioselectivity. Density functional theory revealed that the enantioselectivity in the desymmetrizing reaction arose from the cooperative effects of the IrI species and the HypPhos catalyst. The utility of this methodology is demonstrated by the (formal) syntheses of seven alkaloid targets: (-)-gliocladin C, (-)-coerulescine, (-)-horsfiline, (+)-deoxyeseroline, (+)-esermethole, (+)-physostigmine, and (+)-physovenine.

K0.5Na0.5NbO3 (KNN) crystals have great application prospects due to their excellent piezoelectric properties, high Curie temperature, and environmental friendliness. Currently, KNN crystals grown by the seed-free solid-state crystal growth (SFSSCG) method exhibit relatively high dielectric loss. In order to reduce their dielectric loss, Cu, Bi and Mn co-doped KNN lead-free piezoelectric single crystals were prepared by the SFSSCG method. The effects of the CuO doping content on the structure and electrical properties of (1 − x)(0.996KNN–0.004BiMnO3)–xCuO crystals were systematically studied. The results show that an appropriate doping amount of CuO is beneficial for the growth of the crystals and the improvement of electrical properties. When the diameter of the billets is 40 mm, the maximum crystal size of 25 × 21 × 2 mm3 is obtained. All crystals have a typical perovskite structure almost with a single orthorhombic phase and are very compact almost without holes. The minimum average domain width of 276 nm is obtained for the crystal at x = 0.005. The KNN crystals exhibit normal ferroelectric characteristics and a space-charge-limited-conduction (SCLC) mechanism. The introduction of Cu2+ ions reduces the dielectric loss of the crystal and increases its piezoelectric and dielectric properties. The Cu, Bi and Mn co-doped KNN crystals achieve excellent comprehensive properties: d33 = 314 pC N−1, Pr = 29.9 μC cm−2, Ec = 10.1 kV cm−1, = 869 pm V−1, Qm = 56.8, Kt = 0.38, tan δ = 0.013 and TC = 409 °C. This provides a route to improve the electrical properties of KNN-based crystals. [ABSTRACT FROM AUTHOR]

KNN crystals and solid-state crystal growth method have great application prospects due to their, respectively, outstanding advantages. However, at present there are also some problems that need to be solved urgently. In this work, both of BiCoO3 and CuO were chosen as dopants to further improve the size and piezoelectric properties of KNN-based crystals prepared by seed-free solid-state crystal growth (SFSSCG) method. In particular, the effects of CuO-doping on the growth, structure, and electrical properties were investigated systematically. The results show that Co, Cu, and Bi co-doping can promote the growth of KNN-based single crystals and enhance their electrical properties. The addition of CuO does not change the perovskite crystalline structure of the crystals. When the content of CuO is less than 0.5 at.%, the crystals have a single orthorhombic perovskite structure. And when the content of CuO is 0.7 at.%, a two-phase coexisting structure consisting of orthorhombic and tetragonal phases is present in the crystal. The domains in the crystals are mainly composed of 180° ones and have a parallel lamellar microstructure. The average domain width in the crystals first decreases and then increases with increasing the CuO content. When the content of CuO is 0.3 at.%, the crystals obtain an excellent overall electrical properties of d33 = 498 pC/N, Pr = 28.3 μC/cm2, Qm = 64.9, kt = 0.37, TC = 418 °C, εr = 373, and tanδ = 0.015, implying that they have a promising applications in piezoelectric and ferroelectric devices. [ABSTRACT FROM AUTHOR]

Carbonyl desaturation is a fundamental reaction widely practised in organic synthesis. While numerous methods have been developed to expand the scope of this important transformation, most of them necessitate multi-step protocols or suffer from the use of high loadings of metal or strong oxidizing conditions. Moreover, approaches that can achieve precise stereochemical control of the desaturation process are extremely rare. Here we report a biocatalytic platform for desymmetrizing desaturation of cyclohexanones to generate diverse cyclohexenones bearing a remote quaternary stereogenic centre, by reengineering 'ene'-reductases to efficiently mediate dehydrogenation, the reverse process of their native activity. This 'ene'-reductase-based desaturation system operates under mild conditions with air as the terminal oxidant, tolerates oxidation-sensitive or metal-incompatible functional groups and, more importantly, exhibits unparalleled stereoselectivity compared with those achieved with small-molecule catalysts. Mechanistic investigations suggest that the reaction proceeded through α-deprotonation followed by a rate-determining β-hydride transfer., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)