Latest ArticlesThe metal-free S–S bond exchange reaction of symmetrical disulfides catalyzed by NFSI is described. This novel protocol provides a facile and efficient approach to accessing important unsymmetrical disulfides. Furthermore, this strategy could also be utilized in the late-stage functionalization of amino acids, drugs, and natural products. The broad substrate scope, good functional group tolerance and easy accessibility of catalyst indicate that this strategy affords a green and practical complementary method to various unsymmetrical disulfides.
A catalytic asymmetric hydroxylative dearomatization reaction has been disclosed, and the products can smoothly transform into spiroannulation adducts by simply treated with a base under mild conditions. Novel in-situ generated magnesium catalytic methods are developed by application of combinational ligands. Related concise transformaitons of the spiroannulation adducts have been carried out.
A method for stereoselective construction of Z-monofluoroalkenes by nickel-catalyzed defluorinative coupling of gem-difluoroalkenes in mild conditions was described. The combination of lithium organoborate and ZnBr2 generated in situ lithium aryl zincates, which facilitates the transmetalation step of the nickel-catalyzed cross coupling reaction.
Hybrid quantum mechanics/molecular mechanics calculations were performed to elucidate how [MnIIIporphyrin]+X−-based metal-organic frameworks (MOFs) catalyze the [2 + 1] cycloisomerization of enynes and why zwitterionic MOFs exhibit strong activity in Lewis acid catalysis. The calculations showed that zwitterionic MOFs have a "pure cationic active center" leading to a concerted nucleophilic attack pathway with lower barriers. In contrast, metals with coordinating anions have reduced electrophilicity, resulting in a stepwise radical-type pathway with much higher barriers. Further calculations showed the nature of catalysis was strongly depended on the charge on the anion ligand. A good linear relationship between the NPA charge and barrier was found, and verified by 73 anions with small derivations, which presents a universal adaptive character for various coordinated anions.
A nickel-catalyzed reductive cross-coupling reactions between polyfluoroarenes and alkyl electrophiles is reported to access substituted fluoroarenes through chelation-assisted C–F activation. Diverse primary and secondary alkyl (pseudo)halides can be employed to couple with polyfluoroarenes, showing excellent regioselectivity. Furthermore, the nickel-catalyzed asymmetric cross-coupling of polyfluoroarenes with racemic alkyl halides is preliminarily explored. In addition, the practicability of the title transformation is also demonstrated by total synthesis of losmapimod and an analog as key steps. The developed method exhibits many advantages, including economic catalytic systems, commercially available alkyl electrophiles, and lack of sensitive organometallic reagents.
A new, stable and scalable reagent for deuteriodifluoromethylthiolation (deuterated N-difluoromethylthiophthalimide, PhthSCF2D) has been developed. This reagent can be applied for the photocatalytic radical deuteriodifluoromethylthiolation of various olefins and aldehydes (30 examples). Meanwhile, it can achieve the electrophilic deuteriodifluoromethylthiolation of a series of electrophilic substrates including electron-rich arenes, aryl/vinylboronicacids, alkynes, amines, thiols and β-ketoesters (22 examples). Some complex molecules can also be applied in both radical and electrophilic deuteriodifluoromethylthiolation using PhthSCF2D as the reagent.
While N-alkenoxypyridinium salts are widely used for the synthesis of α-functionalized ketones via umpolung strategy, such approaches are usually limited to special nucleophiles at high temperatures. Herein, we developed an alternative photoinduced N-heterocyclic carbene (NHC)- mediated functionalization of N-alkenoxypyridinium salts with various nucleophiles, including tetramethylammonium azide, secondary amines, aryl and alkyl thiols, and even the challenging C(sp3)-nucleophiles, under mild conditions. A cascade radical-radical coupling/nucleophilic substitution sequence was proposed, wherein the NHC enabled the formation of a photoactive electron donor-acceptor complex for α-iodo ketone synthesis.
Herein, we reported a convenient and efficient multicomponent reaction of indoles, selenium powder and unactivated alkyl halides. This protocol provides a practical, and facile approach for the synthesis of 3-alkylselenindole derivatives. The advantages of this strategy include mild and transition-metal-free conditions, broad functional group tolerance, the use of simple and easily accessible seleniium powder and alkyl halides as coupling partners. More importantly, the reaction proceeded smoothly with a large scale (> 10 g, > 90% yield), which further highlighted the potential application of this selenation strategy.
Ten novel butterfly-shaped dithienobenzosilole-based luminogens, which are peripherally installed with a variety of substituents including hydrogen, phenyl and substituted phenyl groups, have been readily prepared via an iodine-induced intramolecular electrophilic double-cyclisation reaction and subsequent deiodination or coupling reactions. The optical and electrochemical properties of these compounds were systematically investigated to clarify the relationships between their structures and properties, supported by theoretical calculations. These compounds exhibit deep-blue to sky-blue emissions and high photoluminescence quantum yields up to 0.84 in solution and solid states which are regulated by the functional blades and their steric hindrance on the α– and β–positions of thiophene rings. Their high thermal- and photo- stabilities have been revealed and mainly attributed to the dithienobenzosilole core.
To develop efficient concerted companion (CC) dyes for fabricating high-performance DSSCs, three organic dyes XL1-XL3 have been designed by varying the position and number of the β-hexylthiophene (HT) bridges, and these organic dye units are covalently linked with our previously reported porphyrin dye XW10 to construct the corresponding CC dyes XW74-XW76. Among the organic dyes, XL3 contains two β-hexylthiophene units at both the donor and acceptor parts and thus possesses stronger light-harvesting capability in the green light region. Because of the most complementary absorption between XL3 and XW10 as well as the excellent photovoltaic behavior of the individual XL3 dye, the corresponding CC dye XW76 affords the best PCE (10.78%) among all the CC dyes. Upon coadsorption with CDCA, XW76 affords a highest PCE of 11.35%, which outperforms the previous cosensitization system of XW10+WS-5. This work provides an approach for developing efficient DSSCs based on CC dyes composed of an organic dye unit with suitable π spacers inserted at appropriate positions.
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