Palladium-Catalyzed Tandem Hydrocarbonylative Cycloaddition Of Olefins

Functionalized bridged ring compounds,especially bridged ring compounds containing carbonyl structural units,are important intermediates for the synthesis of natural products and pharmaceutical mo lecules,the synthetic method of which has been an important research field in organic synthetic chemistry.The traditionalway for synthesizing carbonyl-containing bridged ring compounds is to utilize Diels-Alder reaction of ester group-containing cyclic dienes with alkenes.However,ester group-containing cyclic dienes usually need to be prepared through a multi-step reaction,which limits thedevelopment ofthis syntheticapproach.In this thesis,we have establisheda Pd-catalyzed tandem hydroesterification/Diels-Alder reaction of o-aldehyde styrene,carbon monoxide and other simple alkenesusing o-aldehyde styrene,carbon monoxide and other simple alkenes as raw materials,which provides a new and efficient synthesticacess to the synthesis of compounds containing carbonyl bridged rings.Initially,we chosen o-aldehyde styrene and as model substrates to proceed the reaction.After systematic condition screening,the optimal reaction conditions were established when using 5 mol%[Pd(allyl)Cl]2as a palladium precursorand 5.5 mol%RuPhos as ligand,together with 5 mol%NH4Cl as cocatalystunder 20 atm of CO atmosphere in anisole for 12 hours under the reaction temperature of 120?.Under this optimized condition,we have concluded a regular cognition after a systematic research for the reaction properties of o-aldehyde styrene,non-aldehyde styrene,1,3-butadiene and simple cyclic alkenes(total of 28 alkenes)withdifferent substituents.These substratesshowed good reactivity and the target product of endo-type was obtained in the yield up to 95%with good chemical selectivity and the diastereoselectivity greater than 20:1.In addition,this reaction has good practicability and the target product can be obtained with high selectivity under gram-scale reaction conditions.The product enables to be converted into functional organic molecules,such as biaromatic hydrocarbons,cyclic ethers and polysubstituted benzocyclohexene by simple functional group transformations including selective reduction,ring opening and decarboxylation aromatization.The mechanism of catalytic reaction was studied in detail through X-ray single crystal diffraction,competitive reaction,control experiment,kinetic experimentand isotope labeling and so on,which indicatedthe reaction belongs to first-order reactions genre and have a zero-order kinetic relationship with CO.A suitable reaction mechanism is proposedon this reseach basis,which lays the foundation for the further development of highly efficient hydrocarbonylation cyclization reactions.