The 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN)‐catalyzed regioselective acylation of carbohydrates and diols in ethyl acetate has been developed. The hydroxyl groups can be selectively acylated by the corresponding anhydride in EtOAc in the presence of a catalytic amount (as low as 0.1 equiv.) of DBN at room temperature to 40 °C. This method avoids metal catalysts and toxic solvents, which makes it comparatively green and mild, and it uses less organic base compared with other selective acylation methods. Mechanism studies indicated that DBN could catalyze the selective acylation of hydroxyl moieties through a dual H‐bonding interaction.
Sugars have always been an important component of drugs, and their design, discovery, synthesis and preparation play an important role in the diagnosis, prevention and treatment of diseases. To synthesize functional oligosaccharides, we need to perform a variety of selective hydroxyl protections of monosaccharides to synthesize functional sugar building blocks. Among these protection reactions, acylation is the most commonly used method to protect the hydroxyl groups in sugars. Regioselective acylation of saccharide hydroxyl groups needs to be achieved by catalysts. How to efficiently synthesize the target products and how to develop more selective, wider ranging, and more environmentally friendly chemical methods are a consistent goal pursued by chemistry researchers. This paper mainly introduces the research progress on six kinds of approaches for the regioselective acylation of sugar hydroxyl groups: those based on organotin, organoboron, organosilicon, metal salts, hydrogen-bonding small organic molecules and enzyme reagents. Finally, the Minireview also summarizes the advantages and disadvantages of these catalysts and prospects for the selective acylation of sugar hydroxyl groups.
Highly regioselective alkylation of sugar hydroxyl groups has always been an important challenge in carbohydrate chemistry, especially for the selective alkylation of trans diols, there is no direct and efficient catalytic method so far. A chiral copper catalyzed universal highly site‐selective alkylation of trans‐diols method is realized. This reaction is performed under mild conditions and has broad substrate scope. The selectivity of the reactions can be controlled by adjusting the copper reagents and the chiral ligands. This method was also applied to the site‐selective modification of drugs and natural products.
Highly strained bifunctionalized dialkyl 2H-thiete-2,3-dicarboxylate 1,1-dioxides are directly synthesized from readily available sulfonyl chlorides and dialkyl acetylenedicarboxylates via the pyridine-mediated [2+2] annulation. In the annulation, pyridine first eliminates HCl from...
The development of low molecular‐weight gelators for the construction of stimuli‐responsive gels is increasing attention because of the great application potential. In this work, we report the design and synthesis of two new naphthalimide derivatives, GSSN and GN, as supramolecular organogelators. GSSN contains a disulfide bond in the molecule, while GN contains no disulfide bond. As a result, only GSSN exhibited reduction responsiveness. A series of tests, including UV‐vis, temperature‐dependent 1H NMR, XRD, and SEM, were carried out to characterize the gelation capability and probe into the gelation mechanism. Results showed that GN can gelate more organic solvents than GSSN. Both hydrogen bonding and π stacking contribute to the gelation. Due to the difference in the assembly of the organogelator molecules, the organogels formed by GSSN and GN presented distinct morphologies. Moreover, strong hydrophobicity was found in the organogel films of GSSN and GN, suggesting potential application as hydrophobic coating materials.
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