Lewis Base-boryl Radical Enabled Borylation Reaction And Decarboxylation Reaction

Free radical reactions represent an efficient and powerful tool to assemble organic molecules in chemo-,regio-,and stereo-controlled manner.Recently,reactions of Lewis base-boryl radicals have attracted extensive attention and numerous useful synthetic applications have been achieved since the seminal work of Brian P.Roberts on amine-boryl radicals and organo-phosphine-boryl radicals.Based on our group's previous works,in this dissertation,the author described the radical borylation reactions of a series of readily available substrates for the synthesis of valuable boryl-handled organic frameworks,such as boron-tethered N-heterocycles and organic fluorines.Further diversifications and modifications of boryl-handled organic frameworks have been demonstrated.It provided a new approach and strategy to access various functionalized N-heterocyclics and organic fluorines.In addition,the author also reported Lewis base-boryl radicals enabled Giese reaction and Barton decarboxylation of NHPI esters under mild reaction conditions,providing a new alternative to achieve decarboxylative functionalization of abundant carboxylic acids.The first chapter summarized three kinds of synthetic applications of Lewis base-boryl radicals:reduction of organic halides,alcohols,gem-dicyanides and thioamides;construction of boryl-hanled organic molecules;boryl radical enabled skeletal rearrangement reaction.The second chapter introduced a radical borylative cyclization of N-allylcyanamides affording diverse boron-hanled N-heterocycles.In this work,the NHC-boryl radical added to the carbon-carbon double bond in a chemo-and regioselective manner.The resulting carbon radical then underwent cyclization to the intramolecular N-CN group,leading to amide-iminyl radical intermedates.The following HAT reaction afforded boron-handled N-heterocyclic compounds,such as cyclic amidines and quinazoliones.It have been found that the use of a thiol compound as the polarity reversal catalyst could inhibit the decynation side product formation.The resulting boron-handled N-heterocyclics could be further transformed to various useful organic building blocks.The third chapter described an interesting regioselective radical hydroboration reaction of gem-difluoroalkenes,affording value-added ?-boryl difluoroalkanes.DFT caculations have been performed to rationalize the remarkable ?-selectivity of this hydroboration reaction.Meanwhile,the resulting ?-boryl difluoroalkanes have been further transformed to diverse monofluoroalkene derivatives.The fourth chapter introduced DMAP-boryl radical enabled decarboxylative Giese reaction and Barton reduction reaction of activated-redox NHPI esters.The reactions proceeded smoothly in a metal-free manner and many functional groups could be tolerated under the mild reaction condition.The present protocol provided a new strategy for decarboxylation reaction.