Study On The Synthesis Of Cyclic Compounds And Carbon - Oxygen Bond By Selective Insertion Strategy Of Acetylene Bond

According to the dictionary of natural products,90%of chemicals discovered in Nature contain either a carbocyclic or a heterocyclic subunit. Among the methods for access to these skeletons, cyclization of alkynes provides an efficient and convenient route. Recently, intramolecular or intermolecular double insertion of triple bonds as a key step has been demonstrated as a powerful strategy for the preparation of polycyclic compounds. Although many methodologies have been established to construct these compounds, the development of more efficient protocols that can generate versatile substituted polycycles from readily available starting materials is in high demand.This dissertation mainly focuses on the synthesis of polycycles via palladium-catalyzed domino reactions involving double insertion of the triple bonds. Moreover, several examples of the research of C-O bond activation are displayed.Firstly, several novel routes for the efficient assembly of polycyclic derivatives from2-alkynylbromobenzene were described. In these protocols, many Lewis-acid-sensitive substances such as o-substituted benzamide, aniline, phenol and2-phenylmalonate could go through double cis-insertion of the triple bonds into C-Pd intermediates with high chemoselectivity and regioselectivity, instead of the direct annulation as reported previously. These strategies showed high efficiency with good functional group tolerance.Secondly, a novel and efficient pathway for the generation of3-(benzofuran-3-ylmethylene)benzofuran-2(3H)-ones via a palladium-catalyzed carbonylative reaction of2-alkynylphenol with carbon monoxide was developed. The reaction proceeded in high yields with good selectivity. A one-pot synthesis starting from2-iodophenol and alkyne was presented as well. During the reaction process, a double insertion of triple bonds was believed to be the key step.Additionally, the palladium-catalyzed C-O bond activation of4-hydroxycoumarins and aryl imidazolylsulfonates was explored. The direct alkynylation and arylation of4-hydroxycoumarins provided efficient access to diverse coumarins, which are important compounds in fine chemistry and pharmaceuticals. Moreover, aryl imidazolylsulfonates were demonstrated to be more reactive among the cross-coupling substances, compared with other traditional sulfonates and esters. The advantages of the cross-coupling reactions of aryl imidazolylsulfonates with H-phosphonates included good substrate generality, high efficiency, and experimental ease.