Study On The Construction Of Spiroketal,Oxime And Isobenzofuran Skeletons Via Oxo-heterocyclization Of ?-Alkynones

?-Alkynones with multiple reactive sites have shown broad application in the construction of natural products and drug molecular scaffolds.In recent years,[4 + 2] cycloaddition of ?-alkynyl ketones have been widely investigated by organic chemists.However,the studies on the oxo-cyclization of ?-alkynyl ketones were relatively few.In this dissertation,?-alkynones as the starting materials were subjected with the reaction of different reagents with both electrophilic and nucleohilic sites and free radical donors,enabling the oxo-cyclization to access 81 examples of spiroketals,xanthenes,and benzofuran derivatives in a simple and efficient manner.The dissertations includes four parts as follows:In the first part,the research progress on oxo-cyclization of ?-alkynones were introduced.Based on the summaries of these documents,the significance and novelty of this dissertation were also described.In the second part,Ag/Br?nsted acid co-catalyzed spiroketalization toward spiroketal derivatives was presented.Starting from ?-alkynyl ketones and para-quinone methides,Ag/Bi NPO4 H co-catalyzed 6-endo-dig oxo-cyclization/[4 + 2] cycloaddition cascades were established,which provided an highly diaseteroselective pathway for the synthesis of diverse spiroketals derivatives with generally good yields via C(sp3)-H functionalization.This catalysis was perfectly compatible with silver catalysts and Bronsted acids,providing a highly efficient and practical method for the construction of spiroketals.In the third part,Ag/Sc synergistic catalytic cyclization was presented.Starting from ?-alkynyl ketones and o-hydroxybenzyl alcohols,their tunable bi-and tri-cyclization cascades for the divergent synthesis of three classes of skeletally diverse o-heterocycles with generally good yields were achieved under mild catalytic conditions.Synergistic silver/scandium catalysis enabled ?-alkynyl ketones and o-hydroxybenzyl alcohols in a 1:2 mole ratio to participate in the transformation,which underwent 6-endo-dig oxo-cyclization and [4 + 2] cycloaddition cascade to efficiently generate spiroketals derivatives with good diastereoselectivity,whereas xanthene derivatives were offered through a silver/scandium co-catalyzed benzannulation and [4 + 2] cycloaddition when the reaction temperature is increased to 100 oC.Besides,the unprecedented hexacyclic spiroketal derivatives were obtained through a catalytic cascade 6-endo-dig oxo-cyclization and two [4 + 2] cycloadditions of ?-alkynyl ketones and o-hydroxybenzyl alcohols in a 3 : 1 mole.In the fourth part,a new palladium-catalyzed cyclization-radical addition for the synthesis of benzofuran derivatives was presented.The reaction of ?-alkynyl ketones with aryl diazonium salt and 1,4-diazabicyclo[2.2.2]octane-bis(sulfur dioxide)adduct(DABSO)was carried out by using Pd(OAc)2 as the catalyst,enabling palladium oxidation insertion/Heck coupling/oxo-cyclization(reductive elimination)/sulfonyl radical addition/single electron oxidation/dehydrogenation sequence to furnish structurally new benzofurans.These reactions did not need any oxidant,featuring highly functional group compatibility and braod scope of substrates.