Studies On Free-Radical Promoted Cross-Dehydrogenative-Coupling Reaction Of Fluorinated Alcohols

The direct C-H bond activation has been of great importance in the field of organic chemistry.Not only due to the significance in basic studies of chemistry but also the short formation of a new C-C bond.In recent decades,this field has been attracting various high efficiency and various strategies have been reported.Among all of these,the activation of theα-OH-C(sp~3)-H bonds of alcohol,is of particular synthetic value because of the direct introduction of hydroxyl.This thesis mainly introduces theα-OH-C(sp~3)-H bonds activation of alcohol.First of all,we summarized the research progress ofα-OH-C(sp~3)-H bonds activation of alcohol in recent decades.Then,we introduced in several radical-mediated strategies developed by our group to selectively activate theα-OH-C(sp~3)-H bond of alcohol to construct C-C bonds efficiently.Finally,we summarize and prospect the research in this field.This thesis mainly contains the following four sections.In the first chapter,recent developments of construction sp~3-α-C-H bond of alcohol were summarized,and this chapter can be devided into three parts,(1)free-radical strategies for C–C construction through selectiveα-OH-C(sp~3)-H activation of alcohol.(2)transition-metal-catalyzed C–C bond construction with alcohols;(3)Directα-OH-C(sp~3)-H functionalization of supercritical alcohols without catalyst.In the second chapter,a C-C formation of an electron-rich N-heterocycle with fluorinatedalcoholisdeveloped.Throughthisradical-triggered cross-dehydrogenative coupling strategy,a wide range of useful building blocks such as C3 hydroxyfluoroalkylated indoles and pyrroles can be site-specifically synthesized.Mechanistic studies indicate a single-electrontransfer initiated radical cycle would be involved.In the third chapter,A free-radical mediated highly ordered radical addition/cyclization/(sp~3)C-C(sp~3)formation domino reaction is developed.Three new C-C bonds are formed one by one in a mixed system.Furthermore,it represents the first example of cascade C-C bond formation via selective functionalization ofα-hydroxyl-C(sp~3)-H in fluorinated alcohols.In the fourth chapter,a free-radical-promoted aryl/heteroaryl C-H silylation using hydrosilane was developed.This cross-dehydrogenative silylation enables both electron-rich and electron-poor aromatics to afford the desired arylsilanes in unique selectivity.A“para-selectivity”was observed.This exceptional orientation is quite different from that in Friedel-Crafts C-H silylation or transition-metalcatalyzed dehydrogenative silylationFinally,we summarized the developments of free-radical-promoted C–C formation through selective activation the sp~3-α-C-H bond of alcohol.Also we proposed the outlook of this field in the end of this thesis.