Studies On The Construction Of Cycloheptene[b]benzofuran And 2-γ-lactone Chromanone Skeletons

Cycloheptene[b]benzofuran and 2-γ-lactone chromanone skeletons are widely spread in bioactive natural products.Therefore,from the perspective of synthesis and activity studies of natural product containing these structural motifs,the development of concise,efficient and general strategies for the construction of these skeletons is of great significance.Accordingly,the main task of this thesis is based on the synthesis of cycloheptene[b]benzofuran skeletons and 2-γ-lactone chromanone skeletons,via[4+3] cycloaddition reaction and I2-catalyzed Michael addition of siloxyfuran to chromones.[4+3] cycloaddition reaction and I2-catalytic vinylogous Michael addition of siloxyfuran to chromones.The contents of this thesis could be divided into the following three parts.Chapter one.Summarization of the [4+3] Cycloaddition Reaction(Review).This chapter focused on the introduction of the progress on the [4+3]cycloaddition.We classified and summarized these reactions,based on the types of cyclization methods and the structural types of seven-membered ring(including single seven-membered ring,endocyclic seven-membered ring,7,5-bicyclic skeleton,6,5,7-tricyclic skeleton and 6,7,5-tricyclic skeleton)respectively.Chapter two.Synthesis of Cycloheptene[b]benzofuran Derivatives via[4 + 3] Cycloaddition ReactionsA series of allyl alcohols based on 2,3-benzo-dihydrofuran skeleton were synthesized,starting from substituted salicylaldehyde.We then developed a novel and convenient approach for the construction of cycloheptene[b]benzofuran skeletons through a Zn Cl2·Et2O-promoted [4 + 3] cycloaddition of these allyl alcohol derivatives with isoprene.This method could achieve the concise synthesis of a series of cycloheptene[b]benzofurans(15 examples)in moderate to good yields(45-88%).Chapter three.I2-Catalyzed Michael Addition of Siloxyfuran to ChromonesIodine is an environmental friendly chemical reagent,and is often used in various organic reactions.In this chapter,,a concise synthetic protocol for the construction of the 2-γ-lactone chromanone skeleton has been achieved through a I2-catalyzed vinylogous Michael addition of siloxyfuran to 2-substituted chromones..This method provides a green,efficient and general method for the synthesis of 2-γ-chromonolactone skeleton.It is worth mentioning that this method can be applied to chromone substrates with both ester group and methyl group at 2-position.Furthermore,this method has a good prospect in the synthesis of natural products containing 2-γ-chromonolactone skeletons.