No abstract

No abstract

A cascade Claisen rearrangement of a well-organized maltol propargyl ether for the construction of polysubstituted salicylaldehydes is reported. This reaction features high atom economy (100 %), as well as catalyst-free and gram-scale conditions. Based on this novel methodology, the total synthesis of hemigossypol, gossypol, and their analogues has been realized.

No abstract

No abstract

Based on the field of ReaxFF, the pretreatment of a lignin−carbohydrate complex model in a choline chloride-based deep eutectic solvent was proposed. The results showed that the β-O-4 ether and glycosidic bonds in the model were broken at an optimal temperature of 373 K. The best pretreatment solvent was choline chloride/lactic acid (1:2), and 40% of the model compounds were decomposed. Free protons in deep eutectic solvents were one of the critical factors in the process of biomass delignification, and thus acidic hydrogen binding donors generally had a high lignin removal rate, but there was no significant correlation with the acidity of the hydrogen bonding donors. In the deep eutectic solvents of choline chloride/lactic acid, the delignification effect tended to decrease with the increase of lactic acid content. The delignification effect of monocarboxylic acid hydrogen bond donors decreased with the increasing molecular chain length, while the opposite effect of delignification was observed for dicarboxylic acids. The molecular dynamics simulations showed that choline chloride/glycerol (1:2) with a slightly weaker hydrogen bonding network could bind better and solubilize the product molecules, with interaction energies of −170.89 and −61.99 kJ/mol with carbohydrates and phenolic compounds, respectively.

No abstract

Main observation and conclusion A TEMPO catalyzed cross‐dihalogenation reaction was established via redox‐regulation of the otherwise complex system of dual electrophilic X+ reagents. Formally, the ICl, BrCl, I2 and Br2 were generated in‐situ, which enabled high regio‐ or stereoselective access to a myriad of iodochlorination, bromochlorination and homo‐dihalogenation products with a wide spectrum of functionalities. With its mild conditions and operational simplicity, this method could enable wide applications in organic synthesis, which was exemplified by divergent synthesis of two pharmaceuticals. Detailed mechanistic investigations via radical clock reaction, pinacol ring expansion and Hammett experiments were conducted, which confirmed the intermediacy of halonium ion. In addition, a dynamic catalytic model based on the versatile catalytic role of TEMPO was proposed to explain the selective outcomes.