Copper-catalyzed Direct Arylations And CDC Reactions Of Heterocylic Compounds

As a powerful tool for the formations of C-C bonds, transition-metal-catalyzed C-H activation is of great importance in organic synthesis field. The traditional transition-metal-catalyzed reactions have many deficiencies, such as longer reaction steps, poor selectivities and undesirable byproducts. Direct arylations and CDC reactions could avoid the above-mentioned problems, and provide more efficient and convenient methods. In recent years, these two types of reactions have been utilized extensively in the synthesis of heteroaromatic compounds with special biological activity.Compared to the noble metals used in transition-metal-catalyzed reactions, the inexpensive, non-toxic, environmentally friendly metals, such as copper catalysts have more immense application prospects. In addition, as the third generation of supramolecular host, calixarenes were widely used in ion recognition and supramolecular catalysis owing to their potential function of mimicing enzyme. This dissertation focus on exploring the direct arylations and CDC reactions using copper as catalyst, meanwhile, modifying calixarene skeleton to synthesize of Salens which were applied to ion recognition. This thesis consists of three parts of research work as follows:Part 1. An efficient, regioselective C-5 arylation of thiazolo[3,2-6]-1,2,4-triazol- es catalyzed by simple copper catalyst was developed firstly. This arylation proceeded smoothly without the assistance of additional catalytic ligands, and tolerated a variety of functional groups (44 examples). A wide range of functionalized thiazolo[3,2-6]-1,2,4-triazole cores were obtained in high yields (up to 99% yield). Possible mechanism of the arylation was also discussed.Part 2. Copper-catalyzed cross-dehydrogenative coupling (CDC) reactions of thiazoles with cyclic ethers were developed as the first example of the CDC reactions between non-benzoazoles and ethers. This reaction proceeded smoothly under mild conditions, and benzothiazoles as the substrates were also well-tolerated. Particularly, the acetals, known as the masked 2-thiazolecarboxaldehydes can be obtained by this CDC reaction when dioxolane was used as a special cyclic ether. A wide range of new thiazoles derivatives (24 examples) were obtained in moderate to high yields (up to 92% yield). Preliminary mechanism and supportive DFT calculations of the CDC reaction were discussed as well.Part 3. Three salen compounds were successfully prepared based on modifying the calix[4]arenes and chiral binaphthols. Then, Salen 4-3 as fluorescent chemosensor was applied to study the recognition of metal cations. The chemosensor showed a pronounced fluorescence response and selectivity to Zn2+ion over other 14 metal ions. In addition, upon the addition of Zn2+ ion, the typical emission peak for Salen 4-3 at 575 nm shows a large enhancement due to the formation of a 1:1 complex. Thus, this system can be applied as chemosensor for detecting metal ions in analytical chemistry.