Transition Metal Catalyzed Cross-coupling Of Tertiary Alkyl Oxalates With Electrophiles

The research contents of this dissertaion include Michael addition reaction of Ni-promoted tertiary alkyl oxalates with unsaturated olefins,Fe-catalyzed vinylation of tertiary alkyl oxalates with 2-halovinyl arenes and Ni promoted hydrogenation/deuteration of tertiary alkyl oxalates with diphenylsilane.The details are as follows.In the first part,reaction of tertiary alkyl oxalates with unsaturated alkenes via Michael radcal addition was developed.The method highlights Zn-mediated reduction of readily accessible dialkyl oxalates derived from tertiary alcohols providing a new efficient approach to C-O bond fragmentation and alkyl radical formation.With Mg Cl₂ as the indispensable additive and Ni as the promoter,trapping the radicals with activated alkenes allows for the generation of alkylated all-carbon quaternary centers.In the second part,a rare and efficient method for the creation of vinylated all carbon quaternary centers via Fe-catalyzed cross-electrophile coupling of vinyl halides with tertiary alkyl methyl oxalates was developed.The reaction displays excellent functional group tolerance and broad substrate scope,which allows cascade radical cyclization and vinylation to afford complex bicyclic and spiral structural motifs.The preliminary mechanistic studies indicated that the reaction proceeds via tertiary alkyl radicals,and the putative vinyl-Br/Fe complexation appears to be crucial for activating the alkenes and enabling a possibly concerted radical addition/C-Fe forming process.In the third part,Zn-mediated hydroreduction of readily accessible tertiary alkyl oxalates was developed,which provided a general,mild and scalable method for C–O bond hydrogenation/deuteration.The method is comptiable with an array of structural motifs bearing diverse functional groups,which has been successfully applied to the synthesis of a key intermediate en route to estrone.In addition,efficient and selective introduction of deuterium（D）at theα-carbon positions of oxalates derived fromα-hydroxyl-carbonyl have been achieved via deoxyaltive of tertiary C（sp³）–O bonds in a single step with excellent deuterium contents,using Ph₂Si D₂/D₂O as the deterium sources.