Transition Metal-catalyzed Decarboxylative Coupling Reactions And Synthesis And Application Of Water-soluble Thiothers

The C-C coupling reaction is one of useful tools in the synthesis of importantmolecules in organic reactions such as natural products, bioactive compounds andmaterials. Compared with the traditional C-C coupling reactions and the C-H activationcoupling reactions, the decarboxylative C-C coupling reactions have some uniqueadvantages. When the carboxylic acids are used instead of organometallic couplingreagents, the byproducts in the decarboxylative C-C reactions are carbon dioxide, whichreduces the cost of the metal waste. In addition, carboxylic acid derivatives are easilyavailable and stable to be handled and stored. Recently, the decarboxylative C-Ccoupling reactions are usually involved in palladium or silver salts as the catalysts,phosphorus compounds as the ligands, excessive silver reagents as the oxidants, highreaction temperatures and strong bases. In this thesis, we attampt to explore the efficientdecarboxylative C-C coupling reactions under the mild conditions, which are brieflydescribed as follows.1. An efficient method of ligand-free Cu-catalyzed oxidative decarboxylativehomocoupling of arylpropiolic acids was developed. When CuI was employed as thecatalyst, I2as the oxidant and K2CO3as the base, the decarboxylative homocouplingreaction for Csp-Cspbond formation in DMSO underwent smoothly to afford thecorresponding1,4-disubstituted1,3-dialkynes in good to excellent yields without anyorganic ligands. Furthermore, unsymmetrical1,3-diynes could be readily prepared byCuI-catalyzed cross-coupling reaction between aryl propiolic acid and terminal alkyne.A proposal reaction mechanism was studied. Comparing with these reports, theadvantages of this method are ligand-free and mild reaction conditions.2. The method of synthesis of1,3-diynes through CuI/1,10-phenanthroline-catalyzedoxidative decarboxylative homocoupling of aryl pioprolic acids in aqueous DMF was developed. The catalytic system was suitable for a variety of aryl pioprolic acids, andthe corresponding1,3-diynes can be prepared in high yields. The catalytic system wasseparated from the organic products by filtration and the residual aqueous DMF solutionshowed activity for several cycles. Comparing with these reports, the advantages of thismethod are readily separation of the productions and recyclable catalytic system.3. In the mixture solvent of1,4-dioxane/acetic acid/dimethylsulfoxide (v: v: v=7.5:1.5:1), the system of Pd(PPh3)4/Ag2O/K2S2O8catalyzed the decarboxylation anddehydrogenation reactions between-oxocarboxylic acids and2–(benzo[b]thiophen–2–yl)pyridine/2–(benzofuran–2–yl)pyridine to prepare bioactivebenzofurans and benzothiophenes derivatives that acyl substituted C-3positions. Thereactions were performed well for all the substrates examined, and the desired productswere isolated in good yields. This method firstly realized the acylation reaction on thefuran and thiophene ring via decarboxylative reaction.4. The new thioethers were synthesized via the simply nucleophilic reaction betweenzwitterionic compand (Tab) and benzyl halide. Because of their good solubility in water,these ligands were employed to promote Suzuki-Miyaura coupling reactions ofarylboronic acid with aryl bromide or iodides mediated by Pd(OAc)2in the presence ofNa2CO3in water under the mild conditions. The corresponding Suzuki-Miyauracoupling products were obtained in good to excellent yields.