Visible Light Induced Reduction and Pinacol Coupling of Aldehydes and Ketones Catalyzed by Core/Shell Quantum Dots.

We present an efficient and versatile visible light-driven methodology to transform aryl aldehydes and ketones chemoselectively either to alcohols or to pinacol products with CdSe/CdS core/shell quantum dots as photocatalysts. Thiophenols were used as proton and hydrogen atom donors and as hole traps for the excited quantum dots (QDs) in these reactions. The two products can be switched from one to the other simply by changing the amount of thiophenol in the reaction system. The core/shell QD catalysts are highly efficient with a turn over number (TON) larger than 4 × 104 and 4 × 105 for the reduction to alcohol and pinacol formation, respectively, and are very stable so that they can be recycled for at least 10 times in the reactions without significant loss of catalytic activity. The additional advantages of this method include good functional group tolerance, mild reaction conditions, the allowance of selectively reducing aldehydes in the presence of ketones, and easiness for large scale reactions. Reaction mechanisms were studied by quenching experiments and a radical capture experiment, and the reasons for the switchover of the reaction pathways upon the change of reaction conditions are provided.

Visible-Light Photocatalytic Synthesis of Amines from Imines via Transfer Hydrogenation Using Quantum Dots as Catalysts.

CdSe/CdS core/shell quantum dots (QDs) can be used as stable and highly active photoredox catalysts for efficient transfer hydrogenation of imines to amines with thiophenol as a hydrogen atom donor. This reaction proceeds via a proton-coupled electron transfer (PCET) from the QDs conduction band to the protonated imine followed by hydrogen atom transfer from the thiophenol to the α-aminoalkyl radical. This precious metal free transformation is easy to scale up and can be carried out by a one-pot protocol directly from aldehyde, amine, and thiophenol.  Additional advantageous features of this protocol include a wide substrate scope, high yield of the amine products, extremely low catalyst loading (0.001 mol %), high turnover number (105), and the mild reaction conditions of using visible light or sun light at room temperature in neutral media.

Visible-light mediated directed perfluoroalkylation of hydrazones.

Perfluoroalkylation of N-alkylhydrazones has been achieved via visible light mediated photoredox reactions between the hydrazone and perfluoroalkyl iodide (RfI). This protocol provides a convenient and efficient access to a series of perfluoroalkylated aromatic aldehyde hydrazones which tolerates a wide range of functional groups on the aromatic ring, and allows the use different types of primary and secondary perfluoroalkyl iodides with up to eight carbon atoms. Furthermore, aliphatic aldehyde hydrazones and N-monosubstituted hydrazones which are unreactive in previously reported hydrazone perfluoroalkylation reactions now take part in the reaction under our reaction conditions to give a satisfactory yield of products. Stern-Volmer quenching studies and spin-trapping experiments indicated that these reactions proceed by free radical addition of the Rf radical to the azomethine atom followed by one electron oxidation of the hydrazyl radical and deprotonation of the diazenium cation.

Long-term efficacy, safety and biocompatibility of a novel sirolimus eluting iron bioresorbable scaffold in a porcine model.

Iron is considered as an attractive alternative material for bioresorbable scaffolds (BRS). The sirolimus eluting iron bioresorbable scaffold (IBS), developed by Biotyx Medical (Shenzhen, China), is the only iron-based BRS with an ultrathin-wall design. The study aims to investigate the long-term efficacy, safety, biocompatibility, and lumen changes during the biodegradation process of the IBS in a porcine model. A total of 90 IBSs and 70 cobalt-chromium everolimus eluting stents (EES) were randomly implanted into nonatherosclerotic coronary artery of healthy mini swine. The multimodality assessments including coronary angiography, optical coherence tomography, micro-computed tomography, magnetic resonance imaging, real-time polymerase chain reaction (PCR), and histopathological evaluations, were performed at different time points. There was no statistical difference in area stenosis between IBS group and EES group at 6 months, 1year, 2 years and 5 years. Although the scaffolded vessels narrowed at 9 months, expansive remodeling with increased mean lumen area was found at 3 and 5 years. The IBS struts remained intact at 6 months, and the corrosion was detectable at 9 months. At 5 years, the iron struts were completely degraded and absorbed in situ, without in-scaffold restenosis or thrombosis, lumen collapse, aneurysm formation, and chronic inflammation. No local or systemic toxicity and abnormal histopathologic manifestation were found in all experiments. Results from real-time PCR indicated that no sign of iron overload was reported in scaffolded segments. Therefore, the IBS shows comparable efficacy, safety, and biocompatibility with EES, and late lumen enlargement is considered as a unique feature in the IBS-implanted vessels.

Photocatalytic Synthesis of Sulfinamides and Sulfoxides from Nitroarenes and Thiophenols.

We present an efficient and versatile visible light-driven methodology for synthesizing sulfinamides and sulfoxides using nitroarenes as the nitrogen source and thiophenols as the sulfur source. The switch-over of the two reaction pathways was achieved by changing the type of photocatalyst and the amount of thiophenol in the reaction mixture. The reaction proceeds under mild conditions with good functional group tolerance and can easily be scaled up.

Long-term safety and absorption assessment of a novel bioresorbable nitrided iron scaffold in porcine coronary artery.

This study aimed to investigate the long-term biocompatibility, safety, and degradation of the ultrathin nitrided iron bioresorbable scaffold (BRS) in vivo, encompassing the whole process of bioresorption in porcine coronary arteries. Fifty-two nitrided iron scaffolds (strut thickness of 70 µm) and 28 Vision Co-Cr stents were randomly implanted into coronary arteries of healthy mini-swine. The efficacy and safety of the nitrided iron scaffold were comparable with those of the Vision stentwithin 52 weeks after implantation. In addition, the long-term biocompatibility, safety, and bioresorption of the nitrided iron scaffold were evaluated by coronary angiography, optical coherence tomography, micro-computed tomography, scanning electron microscopy, energy dispersive spectrometry and histopathological evaluations at 4, 12, 26, 52 weeks and even at 7 years after implantation. In particular, a large number of struts were almost completely absorbed in situ at 7 years follow-up, which were first illustrated in this study. The lymphatic drainage pathway might serve as the potential clearance way of iron and its corrosion products.