Alkyl Carbagermatranes Enabled Synthesis Of Saturated Carbocycle-Fused Aromatics Through Catellani Strategy

Palladium/norbornene co-catalyzed multi-components reaction,also known as Catellani reaction,is capable of realizing functionalization at both ipso(ipso reaction or termination reaction)and ortho(ortho reaction)position on aromatic ring.This domino reaction strategy allows abundant substitution patterns on aromatic ring system,therefore is of great significance in synthetic chemistry.As such,exploring new ortho reaction and ipso reaction has become major topic in the field of Catellani reaction.Since the discovery of Catellani reaction in 1997,its many variants have been developed over the last decades.For instance,ortho reaction has been expanded from original ortho alkylation to arylation,acylation and amination etc.Meanwhile,termination reaction(ipso reaction)is also continuingly developing.Heck-type termination was the first applied and also the most applied one to date,other type of termination,such as arylation,alkynylation,hydrogenation and borylation etc.have also been disclosed by many research groups.In addition,special sp3-C(namely alkyl)terminated Catellani reaction was realized either by using methyl boronic acid as ipso terminating nucleophiles or through cascade C-H bond activation strategy.Until recently,general β-H containing alkyl terminated Catellani reaction has been realized using alkyl carbagermatranes(alkyl-Ge)as terminating reagent by our group.In this dissertation,we started with a review on termination reaction in Catellani reaction and construction of cyclic molecules through Catellani strategy.Based on the above review,we found that the using Catellani reaction to construct carbocyclic ring still lacks a universal method,which is mainly limited by the lack of an orthogonal fragment containing both electrophilic site and nucleophilic site.To overcome this challenge,we have synthesized terminally brominated alkyl carbagermatranes,which contain both terminal electrophilic site and nucleophilic site and then successfully utilized them to construct benzo seven-membered ring systems through a Catellani strategy.This strategy was compatible with various functional group and can be extended to the synthesis of 6-8 membered benzo ring.The modification of natural product derivatives and the synthesis of biologically active molecules further demonstrate the utility of this reaction.