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Discussion
New technologies have been explored in many researches such as a kind of long-acting mucoadhesive thermogels and gallate-loaded gelatin-g-poly (N-Isopropylacrylamide) for the treatment of DED. As the first recommended drug in “Dry Eye Diagnosis and Treatment Guidelines”, the protective effect of LC on corneal epithelial cells under hypertonic state has been verified.
22–24 Another research group prepared an artificial formulation which also used LC as a part of formulation to help replenish the tear film.
25 In this study, a kind of thermosensitive in situ gel of LC was prepared which is in a floating condition at room temperature while can form a gel rapidly as soon as dropped in the ocular surface of rabbits. The mechanism of the gelatinization under specific temperature of LCTG was relevant with hydrophobic effect of groups, hydrogen-bond interaction among polymer chains and hydrogen-bond interaction among hydrophilic group. On the one hand, LCTG can give full
Abstract
Dehydrative cyclization of diols to O-heterocycles is attractive, but acid and/or metal-based catalysts are generally required. Here, we present a hydrogen-bond donor and acceptor cooperative catalysis strategy for the synthesis of O-heterocycles from diols in ionic liquids [ILs; e.g., 1-hydroxyethyl-3-methyl imidazolium trifluoromethanesulfonate ([HO-EtMIm][OTf])] under metal-free, acid-free, and mild conditions. [HO-EtMIm][OTf] is tolerant to a wide diol scope, shows performance even better than H
2SO
4, and affords a series of O-heterocycles including tetrahydrofurans, tetrahydropyrans, morpholines, dioxanes, and thioxane in high yields. Mechanism investigation indicates that the IL cation and anion serve as hydrogen-bond donor and acceptor, respectively, to activate the C─O and O─H bonds of alcohol via hydrogen bonds, which synergistically catalyze dehydrative cyclization of diols to O-heterocycles. Notably, the products could be spontaneously separated after reac