Cationic Palladium(?)-Catalyzed Michael Addition Reaction By Hydropalladation Of Alkynes

In the past few decades,our group developed the palladium?II?catalyzed reactions.Based on our group's previous work,especially the exploration of the cationic palladium catalyzed reactions,this thesis focused on the development of Cationic palladium-catalyzed cyclization of Alkynyl Cyclohexadienones initiated by hydropalladation of alkynes.The major work includs the following parts:1.Cationic Palladium?II?-Catalyzed by hydropalladation of Alkynes with the addition of silver saltUsing Pd?dppf?Cl₂+AgPF₆ as the catalyst and ethanol as the hydrogen source,we realized the reductive cyclization of Alkynyl Cyclohexadienones to give a series of hydro benzopyrrole derivatives Firstly the palladium center captured the?-H of the hydroxyl group to give a hydropalladium active complex.Then the alkyne triple bond inserted into the hydrogen-palladium bond,giving alkenylpalladium species which will add to the ketene.The formed oxypalladium species was easily hydrolyzed to give the cyclization product.This reaction was a totally palladium?II?-catalyzed process.2.Cationic Palladium?II?-Catalyzed by hydropalladation of AlkynesUsing[?dppp?Pd?H₂O?₂]?BF₄?₂ as the catalyst and ethanol as the hydrogen source,A cationic palladium?II?-catalyzed reductive cyclization of cyclohexadienone-containing1,6-enynes by using ethanol as a hydrogen donor and solvent was successfully developed.This procedure offered a convenient access to cyclohexenone-annulated heterocycles under mild reaction conditions.The reaction is initiated by hydropalladation of alkyne and quenched by addition to the intramolecular conjugate alkene and this possible mechanism was preliminarily demonstrated by deuterium-labeling experiments.