| Heterocyclic molecules, such as furans, pyrroles and thiophenes, are important structural units which are found in many biologically active natural and artificial compounds. They are also versatile building blocks in synthetic organic chemistry. The development of efficient approaches to heterocycles received considerable attention in organic chemistry. Aryoxyenynes are important synthetic precursors for heterocycles formation. This thesis focused on the development of novel synthetic methodologies for the synthesis of aryoxyenynes and its further application to the synthesis of five-membered heterocycles, such as2,4-disubstituted furans,2,3,4-trisubstituted furans,2,4-disubstituted pyrroles, and2,4-disubstituted thiophenes. It includes the following five parts:1. Pd-catalyzed synthesis of highly functionalized aryoxyenynes. This methodology was realized by the Sonogashira coupling reaction of alkenyl halides and terminal alkynes in the absence of copper salts. The desired aryoxyenynes were obtained in65%-99%.2. Aryoxyenynes were successfully applied to the synthesis of2,4-disubstituted furans with an ester group at C-4position through Au-catalyzed annulation reaction. Aryl, alkenyl and alkyl substituents on the acetylene terminus were compatible in the annulation reaction, furnishing the desired furans. In this procedure, Au catalyzed two reactions in one-pot, one was the hydrolysis reaction of (E)-1-aryloxy-1-en-3-ynes, and the other was the subsequent O-cyclization reaction. The furans derivatives were obtained with the yields from44%-91%.3.2,3,4-Trisubstituted furans were prepared by the Pd-catalyzed cascade reactions using aryoxyenynes and aryl iodides. Aryl and alkyl substituents could be successfully introduced to the furan ring with good selectivity. The desired trisubstituted furans were obtained in50%-92%yields.4.1,2,4-Trisubstituted pyrroles were synthesized by the Cu-catalyzed cascade reactions using aryoxyenynes and amines. Aryl, alkyl groups on the acetylene terminus were compatible in the annulation reaction, furnishing the desired pyrroles in42%-90%yields. 5. The reaction of aryoxyenynes with K2S afforded thiophene derivatives in good to high yields. This procedure included the cascade reactions of Michael addition/nucleophilic addition without the usage of any catalysts. Aryl, alkyl substituents on the acetylene terminus could be used in the annulation reaction, leading to the desired thiophenes in56%-90%yields.In this thesis,24desired aryoxyenyne derivatives,25furans,13pyrroles, and8thiophene derivatives were synthesized. All compounds were characterized by1H,13C NMR spectroscopy and High Resolution mass spectroscopy. |
