Synthesizing different types of sequence-controlled copolyesters can enrich the diversity of copolyesters and modify their properties more precisely, but it is still a challenge to synthesize a complicated sequence-controlled copolyester using different hydroxy acids in a living polymerization manner. In this work, a highly regioselective and stereoselective catalytic system was developed to synthesize biorenewable and biodegradable copolyesters of mandelic acid and lactic acid with isotactic-alternating, heterotactic-alternating, and ABAA-type precise and complicated sequences. Because of the regular incorporation of mandelic acid into polylactide, these sequence-controlled copolymers of mandelic acid and lactic acid show higher glass-transition temperatures than polylactide and a random copolymer. A stereocomplexation interaction between two opposite enantiomeric isotactic polymer chains was also discovered in the isotactic-alternating copolymer.

The Lewis acidic B­(C6F5)3 was recently demonstrated to be effective for the C–H alkylation of phenols with diazoesters. The method avoids the general hydroxyl activation in transition-metal catalysis. Ortho-selective C–H alkylation occurs regardless of potential para-selective C–H alkylation and O–H alkylation. In the present study, a theoretical calculation was carried out to elucidate the reaction mechanism and the origin of chemo- and regio-selectivity. It is found that the previously proposed B­(C6F5)3/N or B­(C6F5)3/C bonding-involved mechanisms are not favorable, and a more favored one involves the B­(C6F5)3/CO bonding, rate-determining N2 elimination, selectivity-determining electrophilic attack, and proton transfer steps. Meanwhile, the new mechanism is consistent with KIE and competition experiments. The facility of the mechanism is attributed to two factors. First, the B­(C6F5)3/CO bonding reduces the steric hindrance during electrophilic attack. Second, the bonding forms the conjugated system by which the LUMO energy is reduced via the electron-withdrawing B­(C6F5)3. The ortho-selectivity resulted from the greater ortho-C–C (than para-C–C) interaction and the O–H···O and O–H···F hydrogen-bond interaction during electrophilic attack. The greater C–C (than C–O) interaction and the π–π stacking between the benzene rings of phenol and diazoester concerted contribute to the chemo-selective C–H alkylation.

Carbon-11 labelled carbon dioxide is the most common feedstock for the synthesis of positron emission tomography radiotracers, and can be directly used for 11C-carbonylation. Herein, we report the development of an apparatus that takes advantage of “in-loop” technologies to facilitate robust and reproducible syntheses of 11C-carbonyl-based radiotracers by [11C]CO2-fixation. Our “in-loop” [11C]CO2-fixation method is simple, efficient, and proceeds smoothly at ambient pressure and temperature. We selected model 11C-carbonyl labelled carbamates as well as symmetrical and unsymmetrical ureas based on their widespread use in radiotracer design and our clinical research interests for proof-of-concept. Utility of this method is demonstrated by the synthesis of a reversible radiopharmaceutical for monoamine oxidase B, [11C]SL25.1188, as well as two novel fatty acid amide hydrolase inhibitors. These radiotracers were isolated and formulated (>3.5 GBq; 100 mCi) with radiochemical purities (>99%) and molar radioactivity (≥80 GBq/μmol; ≥2162 mCi/μmol).

A practical silver‐catalyzed decarboxylative allylation of α,α‐difluoroarylacetic acids with allyl sulfones is described, which provides a variety of β,β‐difluorinated alkenes in good yields. Notably, the reaction proceeds smoothly in water with good functional group tolerance. The practicality and synthetic value of this process was demonstrated by scaled‐up experiment and elaboration of the products via reduction or Heck reaction. Primary mechanism investigations suggest that a radical process might be involved.

The S-doping of the non-noble metal Fe-N-C single-atom catalyst (SAC) shows key bifunctional role in promoting ORR and OER activity. The controversial views about the enhanced ORR activity, and the...

The palladium-catalyzed cross-coupling reaction of 3-iodochromones, thiochromones, and quinolones with ethyl bromodifluoroacetate in the presence of a copper mediator is reported. Under optimized conditions, all reactions worked well and provided difluoro-containing products in moderate to excellent yields.

An efficienta lkylation method of functionalized alkyl halides under mild nickel-catalyzed C(sp 3 ) À C(sp 2 )S uzuki cross-coupling conditions is described. Thef eatureso ft his approach are excellent functional group compatibility,l ow cost nickel catalyst, and the use of am ild base.T his is also the first successful example of the nickel-catalyzed direct 2,2-difluoroethylation or 2,2,2-trifluoroethylation of aryl-/heteroarylboronic acids.

Rh­(III)-catalyzed redox-neutral C–H olefination of aryldiazene­carboxylates has been realized using arylate esters as the olefinating reagents. This reaction proceeds under mild and redox-neutral conditions, resulting in integration of C–H activation and transfer hydrogenation. The chemoselectivity complements that of previously reported rhodium-catalyzed coupling of the same substrates.