Lewis Acid-Catalyzed Conia-ene Reaction And Transition Metal-Catalyzed Cross-Coupling Reaction

Both Lewis acid-catalyzed Conia-ene intramolecular reaction and transition metal-catalyzed cross-coupling reaction are important protocols for the construction of carbon-carbon bonds. The dissertation mainly discussed the efficient and highly regioselective Lewis acid-catalyzed Conia-ene intramolecular reaction to synthesize five to six-membered rings, and transition metal (copper or palladium) catalyzed cross-coupling reactions.(1) A novel and general copper/silver catalytic system has been developed for the Conia-ene intramolecular reaction. The efficient catalytic system was suitable for both linearβ-alkynicβ-ketoesters and 2-alkynic-1,3-dicarbonyl compounds. In the presence of (CuOTf)₂·C₆H₆ and AgSbF₆ (or AgOAc), a variety of linearβ-alkynicβ-ketoesters were cyclized smoothly in moderate to good yield. Moreover, a number of 2-alkynic-1, 3-dicarbonyl compounds were also cyclized successfully to construct five to six-member rings in moderate to good yield under the same conditions.(2) A cheap, efficient and regionselective ZnCl₂-catalyzed Conia-ene intramolecular reaction was presented. A variety of 2-alkynic 1, 3-dicarbonyl compounds, including inert 2-(pent-4-ynyl)-malonate and 2-acetyl-N, N-dimethylhept-6-ynamide in the earlier reports, underwent the Conia-ene intramolecular reaction successfully using ZnCl₂ as the catalyst. It is noteworthy that only exo-products are obtained regiospecially.(3) Pd(OAc)₂ combined with DABCO (1,4-diazabicyclo[2,2,2]octane) was observed as an efficient catalytic system for the Hiyama reaction. In the presence of Pd (OAc)₂/DABCO, a series of aryl halides were coupled with arylsilanes efficiently to afford the corresponding unsymmetrical biaryl compounds in good yields.(4) TBAF (tefra-n-butylammonium fluoride) was an efficient base for the solvent-free cross-coupling reactions. In the prsenece of Pd (or Cu) and TBAF, some cross-coupling reactions, such as the Suzuki-Miyaura, Hiyama, and Sonogashira reaction, could proceed smoothly and afford the corresponding coupled products in satisfactory yields. No conventional solvents were required. On the contrary, the conventional solvents disfavored this reaction.(5) A simple, mild, and rapid palladium-catalyzed Suzuki-Miyaura cross-couplings of aryl halides with arylboronic acids for the synthesis of biaryls and heterocycle-containing biaryls was described. In the presence of Pd(OAc)₂, NaOMe, and EtOH (or MeOH), a variety of aryl iodides and aryl bromides were coupled with arylboronic acids smoothly in very short time. Notably, the reaction is conducted at room temperature under ligand-free and aerobic conditions.