Utilization Of Biomass-based Green Solvents In Catalysis And Organic Reactions

Solvent is necessary during the reaction and work-up procedure, that contributes to making solvent to be the largest consuming chemical. Nowadays, most industrial solvents are fossil-based volatile organic compounds (VOCs) which are harmful to the environment and humans. As the reserve of fossil resource disappears and increasing environmental concerns about global warming, exploring and utilization of renewable resources is becoming a tendency. Thus, using renewable green solvent as alternative solvent to fossil-based one is an inevitable choice for chemical industry. This thesis focused on exploring some novel biomass-based green solvents or solvent systems, and applying to be reaction media for some organic reactions and biomass activation.Lactic acid is raw material of one of well-known biomass-based green solvents, ethyl lactate. We proposed to utilizing lactic acid as an alternative reaction medium for the first time, and we proved that it presents special effect on many kinds of reactions, such as one-pot three-component reactions of styrenes, formaldehyde and sesamol, N,N-dialkylacetoacetamides or some other active C-H acids, three-component reactions of diethyl acetylenedicarboxylate, aniline and aromatic aldehydes, aniline-catalyzed condensations between diethyl acetylenedicarboxylate and salicyladehydes, and Friedlander annulations between2’-aminoacetophennone and1,3-dicarbony compounds. Lactic acid has a similar molecular size with acetic acid, meanwhile, it has a stronger acidity than acetic acid. Although, acetic acid showed kinds of promotion effect on above-mentioned reactions, much better results were obtained when reactions were conducted in lactic acid. What’s more important, lactic acid is immiscible with non-polar organic solvents, so that we can directly isolate product and reaction medium by liquid-liquid extraction, avoiding neutralization step in acetic acid case.Gluconic acid aqueous solution has been proved to be an effective biomass-based green solvent for lots of traditional acid-catalyzed reactions. In this thesis, we succeeded in realizing the ring-opening reaction of2-substituted-3,4-dihydro-2H-pyrans with some nucleophiles in gluconic acid aqueous solution without using any other kinds of catalysts, such as indoles,1,3-cyclohexanediones, N-methyl aniline, N,N-dimethyl aniline,2-naphthol, and resorcin, giving a series of2-substituted-1,3-dicarbonyl compounds in good to excellent yields. The first example of ring-opening of oxa-Pictet-Spengler product with nucleophiles was also obtained in gluconic acid aqueous solution.In order to enrich diversity of biomass-based green solvents, we constructed a novel green solvent system based on gluconic acid aqueous solution, by adding another biomass-originated chemical, meglumine. In particular, due to the synergy effect between gluconic acid and meglumine, the system performs a "task-specific" solvent for hydroxymethylation of β-ketosulfones. Based on that, we realized a series of one-pot (stepwise) multi-component reactions of p-ketosulfones, paraformaldehyde and another nucleophile, such as styrenes,2-methylfuran, thiophenols or thiols. Besides, it offered us a clean and convenient way to synthesize hydroxymethylation product of β-ketosulfones, so we further conducted some reactions between the hydroxymethylation product and some other nuclephiles in gluconic acid aqueous solution.Finally, we designed and realized dehydration of carbohydrates under catalysis of AlCl3-ChClx@SiO2in the absence of water, on the fact that carbohydrates can readily react with choline chloride to form melts. During the reaction, choline chloride coated on the solid catalyst reacts with carbohydrates to form deep eutectic melts, a liquid; then, liquefied carbohydrates were converted into platform chemicals after effective contacts with active centre of the solid catalyst. Meanwhile, the liquefied carbohydrates can dissolve much more fresh carbohydrates, and platform chemicals formed can be extracted by low-boiling point organic solvent,2-MeTHF or MIBK. We found that several factors will affect efficiency of the catalyst system, such as loading amount of choline chloride on the catalyst, reaction time and temperature, and catalyst amount. Due to the absence of water, side reaction of HMF or furfural with water wasn’t found during the reaction; and the organic phase can extract as much as more than95wt%of the product, due to the presence of silica gel.