Palladium-catalyzed Reductive Heck-type Vinylative Dearomatization Of Unfunctionalized Halonaphthalene Derivatives

Aromatic compounds abundantly existed in the nature have been widely utilized as the initial substrates in some fields,including the synthesis of natural compounds,pharmaceutical intermediate compound and industrial manufacturing.Chemists have obtained many wide and insight research achievements in this field.Furthermore,it has drown wide attention of chemists using the dearomatization strategy of aromatic compounds to construct the heterocyclic or spiro skeletons of complexed molecules.Recently,the rearomatization reaction has achieved considerable development,playing the more and more importmant roles in the synthesis of pharmaceutical,natural products and functional materials.Many reports about dearomatization reactions has been published on international famous academic journal.The scientific investigations in this field have contained the transition-metal-catalyzed dearomatization and reactions utilizing equivalent reagents.Moreover,the transiton-metal-catalyzed dearomatization reactions have shown great potential because of its mild reaction conditions and good generality.However,the substrates in this field have been always concentrated on the functional aromatic or heterocyclic compounds.To date,there have been only a few reports about the catalytic dearomatization reaction of unactivated halonaphthalenes.Our group has successfully developed a noval catalytic dearomatization system and synthesized a series of spiro dearomatic compounds.After we optimized the reaction conditions,we design to use the best conditions as follows: 0.20 mmol 1-iodonaphthalene and 2.5 equiv.4-octyne as the reaction substrates,2.5 mol% Pd2(dba)3 as the catalyst,1.0 equiv.HCOONa as proton source,2.0 equiv.NaOtBu as base,2 mL toluene as the solvent,proceeding in a 25 mL Schlenk tube under the protection of N2 at 120 ? for 12 h with up to 85 % yield.In order to investigate the generality of this catalytic conditions,we synthesized some halogenated naphthalene derivatives substituted by electron donating and electron withdrawing groups,heterocyclic compounds,polycyclic compounds and several alkyne derivatives.We have successfully obtained 12 desired dearomatic spiro compounds charactered by 1H and 13 C after thorough investigation of this catalytic system.This catalytic dearomatization system can be utilized to achieve the direct dearomatization of unfunctional halonaphthalene derivatives,enriching the field of dearomatization system and owning certain research significant in organic synthesis.