Nickel-Catalyzed Regioselective Synthesis Of Organodiboron Compounds

Organoboron compounds are irreplaceable organic building blocks and synthons in synthetic chemistry and the unique reactivity of C-B bond makes related organic transformations and cross-coupling reactions more diverse.Organoboron compounds are usually air and moisture stable and easy to handle compared with Grignard reagents,organolithium reagents.Besides,functional groups could be well tolerated in these reactions involved organoboron compounds.Organoboron compounds have been widely used in polymer chemistry,material chemistry,pharmaceutical synthetic chemistry and life science.Therefore,synthesizing organoboron compounds is full of importance.1,1-diboron and 1,2-diboron compounds formed by two boron moieties bonding to the same or vincinal carbon atoms are new-type multiboron compounds.Diboron compounds possess unique synthetic value compared with monoboron compounds.More complicated and elaborate molecules could be synthesized via further multiple chemical transformations and cross-coupling reactions.In chapter 1 and chapter 2,synthetic methods and applications of 1,1-diboron and 1,2-diboron compounds were reviewed.Key problems and breakthroughs in boron chemistry could be well grasped after fully understanding the update of the two diborons.Synthetic strategies of diborons are limited during the past due to its harsh reaction conditions and tendious synthetic procedures.Construction of two C-B bonds from simple materials(such as alkenes,alkyl electrophiles)to synthesize 1,1-diboron and 1,2-diboron compounds remains a big challenge in boron chemistry.In chapter 3,we reported a nickel-catalyzed reaction to synthesize 1,1-diborylalkanes from terminal alkenes.This reaction presents high chem-and regio-selectivity.Varieties of nonactivated terminal alkenes and styrenes,especially for lower alkenes could be 1,1-diborylated efficiently.In addition,a ten gram-scale reaction to highlight practicality is conducted.This reaction provides an effective and convenient way for synthesis of some useful 1,1-diboron compounds.Borations of alkyl(pseudo)halides to transform C-X bond to C-B bond catalyzed by transition metals are mostly used to synthesize alkyl monoboron compounds.In chapter 4,a methodology constructing two vicinal C-B bonds to synthesize 1,2-diborons from alkyl bromides catalyzed by nickel catalyst was reported.In this reaction,primary,secondary and tertiary alkyl bromides could be well 1,2-diborylated.Some brominated natural molecules were successfully 1,2-diborylated as well.The overall efficiency is subtly influenced when gram scale reactions were conducted.Additionally,this reaction shows good regio-selectivity.