Study On The Cyclization Of Electron-Deficient Conjugated Enyne Derivates Catalyzed By Transition Metals

Gold-carbenes and C-C bond activation have been received much attention in recent years. As for the oxidation of gold-carbenes, though the former methods are highly effective, they produce harmful by-products, so it is essential to develop'green' methods; as for C-C bond activation, there are still no reports on metal-catalyzed C-C bond cleavage of epoxides. Based on our previous works, we prepared enynes and epoxides for the investigation of oxidation of gold-cabenes and C-C bond cleavage of epoxides. There're three parts in this dissertation. PartⅠ:Gold-catalyzed oxidative cyclization of 3-(1-Alkynyl)-2-alken-l-onesWe have developed a protocol for the synthesis of 2-acylfurans from 3-(1-alkynyl)-2-alken-l-ones via gold-catalyzed oxidative cyclization reactions. In this reaction, hydrogen peroxide was used to accomplish the oxidation of gold-cabene intermediates to avoid the harmful by-products. In addition, this system was applied to the oxidative rearrangements of propargyl esters, andα,β-unsaturated aldehydes were obtained in high yield and selectivity. PartⅡ:Gold(Ⅰ)-catalyzed diastereoselective cycloadditions of 1-(1-alkynyl)-oxiranyl ketones and nitrones.We have successfully developed a novel facile strategy towards chemoselective C-C bond cleavage of epoxides by introduction of a alkyne group and a carbonyl group that can be selectively activated by gold catalyst. Furthermore, novel heterobicyclics can be efficiently prepared in a highly diastereo-selective fashion from readily available 1-(1-alkynyl)oxiranyl ketones and nitrones. It is note worthy that this is the first example of a metal-catalyzed, selective C-C bond cleavage of epoxy ketones.PartⅢ:Rhodium(Ⅰ)-catalyzed tandem heterocyclization/carbonylation of 1-(1-alkynyl)-oxiranyl ketonesWe have developed a rhodium(Ⅰ)-catalyzed heterocyclization/carbonylation reaction of 1-(1-alkynyl)oxiranyl ketones under an atmospheric of CO (balloon), leading to highly substituted furo[3,4-6]furan-3(2H)-ones in good to excellent yields. This reaction represents the first example of rhodium-catalyzed C-C bond cleavage of epoxides in a carbonylation process.