The rapid-response ratiometric sensors are promising materials to detect trace water and temperature. However, the accurately visualized water assay in very narrow-range still remains a challenge. Herein, a novel dual-functional...

Owing to the dehydrogenative rearomatization of hydrogenation product and poisoning effect of nitrogen atom, asymmetric hydrogenation of polycyclic nitrogen‐containing heteroaromatics is still a great challenge. Herein, through in situ protection of hydrogenation products with acetic anhydride to inhibit rearomatization and poisoning effect, a novel iridium‐catalyzed enantioselective hydrogenation of polycyclic nitrogen‐containing heteroaromatics – pyrrolo/indolo[1,2‐a]quinoxalines and phenanthridines – has been successfully developed, providing a facile access to chiral dihydropyrrolo/indolo[1,2‐a]quinoxalines and dihydrophenanthridines with up to 98% ee. The strategy features broad substrate scope, easy operation and potential medicinal application.magnified image

The precise synthesis of chiral poly­(silyl ether)­s remains a challenge, in contrast to the well-studied preparation of poly­(silyl ether)­s. Herein, an unprecedented approach for the synthesis of optically active poly­(silyl ether)­s with main-chain chirality has been developed via CuH-catalyzed hydrosilylation polymerization of diketones and silanes. The polymerization features low catalyst loading, mild condition, and broad substrate scope, including a wide range of aromatic diketones and heteroaromatic diketones with excellent yields and enantioselectivities (up to 98% yield and 99% ee). Thermal analysis indicated chiral poly­(silyl ether)­s exhibit good thermal properties. These enantiomerically enriched poly­(silyl ether)­s with good thermal stability have a promising application in chiral separation.

Poly­(silyl ethers) (PSEs) are promising degradable materials, and the development of an efficient method to produce them from readily available materials is highly desirable. Herein, we present a dehydrocoupling polymerization of AB-type silyl alcohol monomers catalyzed by homogeneous iridium­(I) complexes bearing a bisphosphine ligand. A series of PSEs containing aliphatic or aromatic linkers have been synthesized. The PDI of PSEs could be tuned by varying the ligand of iridium/bisphosphine complexes. Moderate to high yields of polymers with number-average molecular weights (M n) up to 9.27 × 104 were obtained. The PSEs possess good thermal stability and low glass-transition temperature (T g = −42 to −83 °C).

Short gram‐scale asymmetric syntheses of asperazine, pestalazine A, and their unnatural congeners thereof, have been achieved in ≈10 steps by using readily accessible starting materials. The nickel‐catalyzed reductive coupling protocol was utilized as a key step for the direct construction of C3asp3−C7′sp2 bond furnishing the diaryl‐substituted quaternary carbon centers with remarkable steric hindrance. The streamlined access to this core structure of heterodimeric tryptophans under the mild reaction conditions, makes this strategy hold a great promise in the concise synthesis of other relevant oligomeric pyrroloindoline alkaloids with unique C3a−C7′ linkages.

No abstract

The spoilage and forgery of perishable products such as food, drugs, and vaccines cause serious health hazards and economic loss every year. Developing highly efficient and convenient time−temperature indicators (TTIs) to realize quality monitoring and anticounterfeiting simultaneously is urgent but remains a challenge. To this end, a kind of colorimetric fluorescent TTI, based on CsPbBr 3 @SiO 2 nanoparticles with tunable quenching kinetics, is developed. The kinetics rate of the CsPbBr 3 -based TTIs is easily regulated by adjusting temperature, concentration of the nanoparticles, and addition of salts, stemming from the cation exchange effect, common-ion effect, and structural damage by water. Typically, when combined with europium complexes, the developed TTIs show an irreversible dynamic change in fluorescent colors from green to red upon increasing temperature and time. Furthermore, a locking encryption system with multiple logics is also realized by combining TTIs with different kinetics. The correct information only appears at specific ranges of time and temperature under UV light and is irreversibly self-erased afterward. The simple and low-cost composition and the ingenious design of kinetics-tunable fluorescence in this work stimulate more insights and inspiration toward intelligent TTIs, especially for high-security anticounterfeiting and quality monitoring, which is really conducive to ensuring food and medicine safety.

The synthesis and characterization of chiral polymers with diverse structure remain a long-term challenging research topic. Herein, a copper-catalyzed enantioselective insertion of carbene into Si-H bond was applied to polycondensation, giving a new type of optically active degradable polyesters containing Si-C bond in the main chain. The polymerization features mild condition, broad substrate scope, excellent yields and enantioselectivities. Chiral diols could be obtained via reduction of optically active polyesters. Thermogravimetric analysis indicated these chiral polyesters exhibit good thermal stability.