FeS redox power motor for PDS continuous generation of active radicals on efficient degradation and removal of diclofenac: Role of ultrasonic.

Diclofenac (DCF), as a typical representative of PPCPs, has potential ecotoxicity to the water environment. In this study, ultrasound (US) enhanced ferrous sulfide (FeS)-activated persulfate (PDS) technology (US/FeS/PDS) was used to degrade DCF. By comparing the degradation effects of US, US/PDS, FeS/PDS and US/FeS/PDS systems on DCF, this study confirmed the synergy and strengthening effects of US. The influences of single-factor experimental conditions on the US/FeS/PDS system were investigated and optimized. The FeS catalysts before and after the reaction were characterized and analyzed by X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The heterogeneous reaction proceeded on the surface of FeS, and a small part of FeS2 was formed on FeS surface. During the reaction, the proportion of S2- on the catalyst surface decreased from 51% to 44%. Correspondingly, the proportion of Sx2- increased from 21% to 26%. It indicated that S2- was oxidized into Sx2- in the reaction, and the loss electrons of S2- caused the reduction of Fe3+ to Fe2+on the FeS surface, which promoted the cycle between Fe2+ and Fe3+ in turn. Furthermore, SO4- and ‧OH were the main active free radicals, of which the contribution rate of ‧OH was about 34.4%, while that of SO4- was approximately 52.2%. In US/FeS/PDS, the introduction of US could promote the dissolution of iron on the FeS surface. US contributed to the formation of a redox power motor between S2-Sx2- and Fe2+-Fe3+, which continuously decomposed PDS to generate sufficient active SO4- and ‧OH radicals, thereby efficiently and continuously degrading DCF. Finally, the related mechanism of DCF degradation by US/FeS/PDS was summarized. Overall, US/FeS/PDS can not only efficiently degrade and remove DCF, but also has potential application value in organic pollution removal and wastewater purification.

Total Synthesis of Aplysiasecosterol A.

Aplysiasecosterol A (1) is a structurally unusual 9,11-secosteroid isolated from the sea hare Aplysia kurodai. We have accomplished the first and asymmetric total synthesis of 1 in a convergent fashion. The left-hand segment bearing three adjacent stereocenters was constructed through desymmetrizing reduction, ketalization, and radical cyclization. A strategy of asymmetric 2-bromoallylation followed by spontaneous desymmetrizing lactolization enabled a more expeditious access to this segment. The right-hand segment was prepared through two different approaches: one featuring Myers alkylation and Suzuki-Miyaura coupling and the other relying upon Aggarwal lithiation-borylation and Zweifel-Evans olefination. The two fragments were coupled by a Reformatsky type reaction. The three consecutive stereocenters embedded in the central domain of 1 were generated by an iron-mediated, hydrogen atom transfer based radical cyclization reaction.

Total Synthesis of Hybridaphniphylline B.

Hybridaphniphylline B (1) is a Daphniphyllum alkaloid possessing 11 rings and 19 stereocenters. Here we report the first total synthesis of 1 featuring a late-stage intermolecular Diels-Alder reaction of a fully elaborated cyclopentadiene and asperuloside tetraacetate. The diene was prepared on the basis of a scalable route to daphnilongeranin B (4). Claisen rearrangement of an allyl dienol ether was exploited as a key step; the subtle variation of the substrate and use of protic solvents suppressed the undesired Cope rearrangement. Daphniyunnine E (6) and dehydrodaphnilongeranin B (7), two congeners of 4, were also synthesized. The dienophile arose from (+)-genipin through glycosylation and lactonization. A one-pot protocol was developed for the diene formation and Diels-Alder reaction; one of the cycloadducts was converted into 1 through reductive desulfurization and global deacetylation.