Synthesis Of Polyboron Compounds And Silole Derivatives Based On Direct Functionalization Of C–H Bonds

The synthesis and application of organoboron and organosilicon reagents are important branches in organic chemistry due to their unique chemical and physical properties.Recently,methodology exploration based on C–H bond cleavage has gained great development,providing an atom-and step-economical approach to many classes of organic compounds.Among these achievements,C–H borylation has evolved from a metal-participated stoichiometric transformation to a reliable and efficient metal-catalyzed process.Although relatively less explored,C–H silylation also gained a great breakthrough in recent years.Based on C–H bond cleavage,this dissertation will include the exploration towards the synthesis of polyboron compounds and silole derivatives.The preface mainly includes the introduction to the masked boronic acids and the synthesis and application of polyboron compounds.Synthetic methods towards silole derivatives are also described.The synthesis of polyboron reagents and their application for modular organic synthesis is reported in Chapter 2.Taking advantage of Ir-catalyzed(hetero)aryl C–H borylation of readily available aryl B(MIDA)reagents,a series of molecules containing two differently masked boronyl groups,B(MIDA)and B(pin),are obtained and then applied into the orthogonal Suzuki–Miyaura coupling reactions based on the discrimination of different boron sites.B(pin)moiety reacted selectivity and the left intact B(MIDA)moiety would then be also utilized efficiently in Suzuki–Miyaura coupling reactions under aqueous basic conditions.This provided a modular reaction process towards substituted arenes via consecutive cross-coupling reactions.The naphthalene-1,8-diaminoborylation of aryl halides is described in Chapter 3.Employing the non-symmetrical diboron compound,B(pin)-B(dan),as the borylating reagent in Pd-catalyzed Miyaura borylation reactions,the chemoselective B(dan)moiety transfer to various aryl rings is realized,yielding masked boronic acids directly from abundant and cheap aryl halides.The usefulness of this naphthalene-1,8-diaminoborylation reaction is demonstrated in the preparation of boron-differentiated polyboron compounds.In addition,the boron-selective Suzuki–Miyaura coupling reaction between B(dan)and B(MIDA)groups is also achieved for the first time.Intramolecular homolytic aromatic silylation of biphenyl-2-hydrosilanes via silyl radicals has been developed for the synthesis of silafluorenes.Moreover,silaindenes are synthesized via a silyl radical cascade process,assembling internal alkynes with readily available arylhydrosilanes.In this one-step reaction,C–H and Si–H bonds are cleavaged and new silicon-containing five-membered cycles are generated.This may represent not only a new simple and efficient approach towards the synthesis of silole derivatives but also a new strategy for C–H silylation reactions.This silyl radical strategy is presented in Chapter 4.In addition,this dissertation also includes two other subjects in Chapter 5,corresponding to my assistant contribution in DFT study on mechanism research and the design and utilization of bidentate boryl ligand in supporting organometallic catalysis.Chapter 6 describes the details for experiments mentioned in this dissertation.