Studies On Some New Methods And Technologies In Synthetic Organic Chemistry

The development of new synthetic methods and technologies is one of the most important areas in organic chemistry. In this thesis, we studied on photocleavable linker, new method and technology for the synthesis of benzimidazoles, and new procedure for Heck reation. The results are below.1,We developed a new photocleavable linker based on PEG-supported 2-methylphenacyl esters. The linker was selectively cleaved by 280-366 nm UV irradiation to give the carboxylic acids in high yields and purities. Compared with published linkers, this kind of linker has several advantages including: (1) simple procedure; (2) excellent photocleavable efficiency; (3) mild reaction conditions; and (4) broad substrate scope (the linker was suitable for aliphatic, aromatic and unsaturated carboxylic acids).2,We developed a simple and efficient method for the synthesis of benzimidazoles from aldehyde and o-phenylenediamine using iodobenzene diacetate as an oxidant. Compared with the published methods, the advantages of the present procedure include: (1) broad substrate scope (both electron-rich and electron-deficient benzaldehydes as well as heteroaromatic aldehydes gave 2-aryl-benzimidazoles in good to excellent yields); (2) mild reaction conditions (the reaction could be carried out well at room temperature and neutral conditions); and (3) the fast reaction times (3-5 min).3,We developed a new technology for the synthesis of benzimidazoles using microfluidic chip reactors. The microscale reaction was performed by introducing the solution of benzaldehyde and phenylenediamines in ethanol, and the solution of iodobenzene diacetate (IBD) in ethanol through the two inlets of the Y-shaped microfluidic chip reactor at ambient temperature. Compared with the routine round-bottom flask, the reaction of aromatic aldehydes and phenylenediamines to benzimidazoles in the microfluidic chip was more efficient due to the fast distribution of the reactants. 4,We developed an efficient and rapid ligand-free Heck reaction under microwave irradiation and solvent-free conditions using Pd(OAc)₂/K₃PO₄ as catalyst. Compared with the published methods, the advantages of ours are as follows: (1) avoidance of expensive ligands and additives; (2) fast reaction times (20-25 min); (3) reasonably good yields; and (4) avoidance of toxic solvents.