Synergistic Silver Sulfadiazine/Quaternary Ammonium Salts-catalyzed Fixation Of CO₂ At Atmospheric Pressure Via The Three-component Reaction

Organic carbonates have been frequently associated with numerous applications involving as nonprotic solvents,electrolyte solvents,precursors for polycarbonates synthesis,and useful intermediates in organic synthesis etc.Traditionally,cyclic and acyclic carbonates generally prepared through the use of toxic phosgene and carbon monoxide.Since CO₂ is an abundant,renewable and nontoxic C₁ building block,it has been accepted as an ideal carbonyl source in view of green chemistry and sustainable development.However,harsh reaction conditions such as high temperature and pressure,as well as a large excess of electrophile are indispensable in CO₂ conversion because of its low reactivity.Therefore,it is significant to synthesize organic carbonates under mild conditions.In this thesis,a thermodynamically favorable three-component cascade reaction of CO₂,propargylic alcohol,and vicinal diol/monohydric alcohol was used to synthesize organic carbonates.A synergistic catalytic system of silver sulfadiazine/quaternary ammonium salts was designed to catalyze the reaction under mild conditions,especially at atmospheric CO₂ pressure.This catalytic system overcame the problems of high temperature and pressure,dependence on organic solvents and insufficient catalytic activity in the reaction.The details are as follows:1)An efficient silver sulfadiazine/Et₄NBr synergistic catalytic system was developed for the three-component cascade reaction of CO₂,propargylic alcohols,and vicinal diols.The cyclic carbonates andα-hydroxyl ketones were simultaneously synthesized under atmospheric CO₂ pressure for the first time.Compared with the previous works,the excellent yield and selectivity of target product were obtained in the absence of any solvent with a lower catalytic amount（5 mol%）and stoichiometric reactant.The catalytic system with a simple process also had a wide substrate scope.Notably,the study revealed that the excellent performance was ascribed to simultaneous activation of hydroxyl group in propargylic alcohols/vicinal diols by silver sulfadiazine,and synergistic effect of bulkier Et₄N⁺in the procedure of intramolecular nucleophilic cyclization confirmed by the stepwise reactions and nuclear magnetic resonance spectrum.2)β-Oxopropyl carbonate is an important intermediate in the synthesis of chemicals and pharmaceuticals.The three-component reaction of CO₂,propargylic alcohols and monohydric alcohols is an effective method to prepareβ-oxopropyl carbonates in view of green chemistry and sustainable development.The silver sulfadiazine/ⁿBu₄NBr synergistic catalytic system was demonstrated to be efficient in the reaction under atmospheric pressure of CO₂ and solvent-free condition.It has overcome obstacles such as high pressure,high catalytic amount,and the use of large amounts of organic solvents in the previous works.The simple method tolerated a wide substrate scope and the yield ofβ-oxopropyl carbonates was up to 99%.The results of the stepwise reactions and control experiments indicated that the synergistic effect between silver sulfadiazine and ⁿBu₄NBr played an important role in promoting the reaction.In addition,the further exploration of nuclear magnetic resonance and fourier infrared spectroscopy revealed that silver sulfadiazine could simultaneously activate the hydroxyl groups of propargylic alcohols and monohydric alcohols.