Study On Oxidative Dearomatization Induced Cyclobutane Ring Expansion And Rearrangement

In recent years,whether for theoretical or practical purposes,small and tensile molecules have long attracted the research interest of synthetic chemists.Among the tensioned carbocyclic ring systems,the cyclopropane ring system has attracted the most attention of chemists.However,for a long time,the value of its homologue-the cyclobutane ring system has not been well explored.For common four-membered ring compounds,due to the existence of ring tension in the structure,the stability of the corresponding chemical bond is poor,and the compound has high chemical activity.The process of rearrangement from four-membered ring expansion to five-membered ring is accompanied by the release of a large amount of ring tension,which is beneficial to the smooth progress of the reaction.At present,we can quickly construct four-membered ring substrates through the development of more mature [2+2] dimerization reactions and introduction of cyclobutanone building blocks.Fortunately,in the past few decades,using the high tension of the four-membered ring as the driving force,the catalytic ring expansion reaction of the four-membered ring system substrate has also been relatively vigorously developed during the catalysis of acid spans the process of enzymatic catalysis.These reactions help the synthesis of multifunctional building blocks,thereby stimulating a series of downstream reactions,and countless interesting reactions can be efficiently realized.The structure of cyclopentane is widely present in many complex natural products,and there are many effective methods in the synthesis of such natural products.Among them,the tension of cyclobutane itself is used as a driving factor to induce ring expansion and rearrangement to form the desired cyclopentane structure.The spiro [4.5] decane skeleton structure is included in the structure category of the cyclopentane skeleton.It is widely found in natural products in nature.For example,the two natural flavanoids Dragonbloodins A1 and A2,which are extracted from the traditional Chinese medicine Sanguis Draconis,have this type of core skeleton structure.The hypervalent iodine organic compounds generated in situ have many advantages such as atom economy,mild reaction performance,and green pollution-free.They perform very well in reactions such as oxidative dearomatization and transition metal-mediated asymmetric catalysis.Iodobenzene acetate（DAIB）has been widely used as an excellent organic hypervalent iodine compound.The use of iodobenzene acetate as an oxidizing agent to oxidize and dearomatize phenolic structures is to generate benzoquinone carbocations,and then perform various classic methods of follow-up reactions.The main content of this project includes: synthesizing a series of phenolic substrates with cyclobutyl non-hydrogen substitution,and using organic hypervalent iodine compounds to carry out oxidative dearomatization and rearrangement reactions for these substrates.The construction of spiro [4.5] decane framework has carried out systematic research work.Specifically,iodobenzene acetate is used as a relatively mild oxidant,and hexafluoroisopropanol（HFIP）is used as the reaction solvent.This type of substrate successfully realizes the construction of a stable spiro [4.5] decane skeleton at room temperature,and the reaction is very simple and fast,which has a wide range of applicability.If it can be reasonably applied to the synthesis of natural products,it can simplify the synthesis route and become a bright spot in the synthesis.