Asymmetric Dearomatization Reactions Of β-Naphthols With N-（2-Iodophenyl） Allenamides

Indole terpenoids are an important of natural products,which is widely concerned by chemists due to unique molecular structures and various biological activities.Therefore,it is of great significance to develop efficient synthetic methods for indole terpenoids.The Heck reaction is an effective method for constructing heterocyclic frameworks such as indole.However,the example using phenol as the nucleophilic reagents to trap C-Pd intermediate followed by the dearomatization process,is rarely reported.We chose 1,3-dimethylnaphthol and N-（2-iodophenyl）allenamine as template reaction substrates.A series of screenings were carried out in the presence of[Pd（C₃H₅）Cl]₂.When the[Pd（C₃H₅）Cl]₂ and chiral phosphoramidite ligand L8 were employed,the Heck dearomatization reaction proceeded smoothly,and afforded the desired products in 88%yield and 92%ee.The protecting groups of allenamide substrates showed greater influence on the ee value of the products,the benzenesulfonyl groups gave the desired products in good yield and enantioselectivity.The different substituents on allenamines afforded the dearomatization products with moderate yield and high enantioselectivity.We found that the 3-position ofβ-naphthol has a great influence on the reaction.When the 3-position substituent is bromine atom,the poor ee value was obtained.When the 3-position were replaced by ethyl,phenyl and allyl,the yield and enantioselectivity of the corresponding products were maintained.After recrystallized,the enantiopurity of the products 3aa in the mother liquid was improved to an excellent level（>99%ee）,and the absolute configuration of 3aa was determined to be S-configuration by X-ray crystallographic analyses.In addition,a series of the transformations of the rac-3ba were carried out to obtain the indole-terpenoid analogues.The structural characterizations were determined by ~1H NMR,¹³C NMR,HPLC,and HRMS.In summary,we have developed the heck cyclization/asymmetric dearomatization cascade reaction ofβ-naphthol with N-（2-iodophenyl）allenamines.This method has the advantages of simple and mild conditions,high yield,wide range of substrates,and has good potential application value.