Study On Solid Acid-base In Organic Heterogeneous Catalysis

The chemical industry is successful but traditionally success has come at a heavy cost to the environment. With the increasing environmental pressure and the public concern to sustainable development, green chemistry is widely recognized by government, academia and industry. Green chemistry, namely environmentally benign chemistry or clean chemistry, is the design, development, and implementation of chemical products and processes to reduce or eliminate waste at source. It further covers reducing the chemical impact of feedstocks and products on huamn health and environment. The ways to achieve clean synthesis are grouped into two categories: the innovation in catalysts and use of alterlative solvents. On the one hand, the work on catalysts greening involves the preparation and application of enzymatic, biomimetic, enantioselective and water-soluble organic metal catalysts to increase enantioselectivity and atom-economy. On the other hand, in order to recover and reuse catalysts, immobilization homogeneous catalysts and utilization of solid catalyst may be the mothod of choice. Finally, the alterlative solvents instead of flammable, volatile or toxic organic solvents have been one of the hot subject in green chemistry. The renewed ones include water, perfluorocarbon, ionic liquid, supercritical liquid and even solvent free.Now, solid acid/base catalysis is one of the economically and ecologically important fields in catalysis. The solid acid and base catalysts have many advantages over liquid Bronsted and Lewis acid/base catalysts. They are noncorrosive and environmentally benign, presenting fewer disposal problems. Their repeated use is possible and their separation from products is much easier. Furthermore, they can be designed to give higher activity, selectivity and longer catalyst life. Therefore, the replacement of the homogeneous catalysts with the heterogeneous ones is becoming even more important in chemical research. Solid acid-base catalysis is beneficial both from the view of economical and environmental point.On the other hand, solvent-free reaction avoids using toxic or volatile organic compounds. It has many advantages: reduced pollution, low costs, simplicity in process and handling. Usually, rate, yield and selectivity in sovlent-free reation may be higher than that in sovlents. It is an ideal option in solvent alteration.In this dissertation, we discussed several solid acids/bases in heterogeneous catalysis and solvent-free reaction.Firstly, the background and significance of green chemistry are introduced in the chapter I. Therefore, solid acid/base in heterogeneous catalysis was put forward as our subject under the umbrella of clean synthesis.In the chapter II, the application of macroporous sulphonic resin (NKC-9) was studyed. First of all, the sturcture and property of NKC-9 was introduced in section 1. Its use in organic catalysis was also given herein. In section 2, an expeditious synthesis ofα,α'-bis (substituted benzylidene)cycloalkanones via cross-Aldol condensation catalyzed by NKC-9 was described. It was the first example of supported acid in the reaction. The catalyst was recovered easily and could be reused for subsequent reactions, according with economical and environmental demands. It showed good chemoselectivity for aromatic aldehydes. Meanwhile, unlike its homogeneous counterparts, it didn't afford the mono-aldol product. We presented its catalytic application in the synthesis of benzoxanthene by the condensation of 2-naphthol and aldehydes in section 3 via tandem intermolecular and intramolecular dehydration. The method was suitable for both aromatic aldehydes and aliphatic ones, while the former gave better results. On the basis of section 3, we further applied the catalyst in multi-component reaction by introduction another substrate, ureas or Amides. Consequently, some amidoalkyl naphthols were achieved in good to excellent yields. The catalyst also showed interesting chemoselectivity. It was applicable to benzamide, acetamide and acrylamide instead of formamide. As for ureas, it was rather complicated. Urea and N-methyl urea gave complex mixutures. Forthermore, N, N'-urea such as diphenylurea kept unchanged under the same condition.Chapter III was mainly involved the study on sulfamic acid (SA). In the section 1, its structural characteristics and special properties were present. Then the extensive literature survey on SA in organic synthesis was made. In section 2, the synthesis of bisindoles in the presence of SA under solvent-free condition was reported. The reactions were performed under ambient temperature in most cases. By comparation to that in solvent, acceleration in rate was observed in solventless method. SA also could catalyze the synthesis of physiologically interest triindolylmethane/ethane from indoles and orthoformate/orthoacetate. The ultrasound irradiation could accelerate the reacion rate. This content was arranged in section 3. In section 4, we examined its catalytic activity in Michael addition of nitroolefins with indoles or pyrrole. The addition ofβ-nitrostyrene with indole was rather slower than that of pyrrole. It took over 12 hours for the former to complete, while the latter only needed 6 hours. The fromer would finish in half an hour under heating.In chapter IV, potential solid catalyst montmorillonite K10 was considered. In section 1, essential properties and recent examples prompted by K10 were given. In section 2, K10 could efficiently catalyze the conjugate additon of indole with nitroalkenes. The 3-alkylation product of indoles were obtained exclusively, an exception was that 3-methyl indole occurred at 2-position of indole.In chapter V, a solid base (Fluorapatite) was dicussed. Unlike acid catalysts, the Michael addition of nitroolefi was less explored in the presence of base. We also reasoned that it was bifunctional catalyst, namely there were acidic and basic sites on the surface. A plausible mechanism by base was brought forward.In chapter VI, the synthesis of 2,2-chloromethylbenzimidazole derivatives has been developed for the first time. The method had the advantages of mild reaction, without any solvent and catalyst. We tried to draw up the mechanism.