Copper-catelyzed Borylcupration Of Allenes And Alkynes With Bis(Pinacolato)Diboron

Allenes are a class of compounds with a cumulative diene functionality, of which two π-orbitals are perpendicular to each other leading to an axial chirality. With the rapid development of allene chemistry during the past few decades, allenes are playing a more and more important role in organic synthesis, Pharmaceuticals, as well as materials science. On the other hand, organoboron compounds are versatile synthetic intermediates that have been widely used in various organic reactions. Thus, the development of efficient and convenient methods for the synthesis of these compounds are of high interest. Herein, we wish to discuss the borylation reactions of allenes for the purpose of affording some new organoboron compounds, which are difficult to access via the traditional approaches, by solving the issues of regio-and stereoselectivity.In this dissertation, my attention has mainly been focused on the transition metal-catalyzed borylcupration of allenes with bis(pinacolato)diboron. Some highly regio-and stereoselective borylcupration reactions have been realized by applying a ligand effect. Finally the chemistry has been extended to alkynes. The whole dissertation may be divided into four parts:Part1:We have realized the highly selective borylcupration of allenes. The regio-and stereoselectivity are controlled by the choice of different ligands. In the presence of tris-(para-methoxyphenyl)phosphine [P(C6H4OMe-p)3], the reaction of aryl-1,2-dienes affords2-alken-2-yl boronates as the only product with exclusive Z-geometry; the regioselectivity is switched to afford the1-alken-2-yl boronates as the major products when the bidentate phosphine2,2’-bis(diphenylphosphino) biphenyl is used as the ligand.Part2:As a continuous effort in this field, we have further studied the highly selective catalytic borylcupration of multi-substituted allenamides. The reaction could proceed smoothly using K2CO3as base to produce Z-β-borylated β,γ-unsaturated enoamides exclusively. Due to the unique effect of amide-group, perfect regio-and stereoselectivity have been achieved, which were rationalized by a DFT study. We have also investigated the asymmetric synthesis with chiral Bn-BOX as the ligand with a highest ee of78%.Part3:We have established an efficient protocol for the synthesis of Si-B dimetallic compounds via copper-catalyzed borylcupration of allenylsilanes with B2(pin)2. By choosing a suitable ligand, the selective synthesis of a-silylallylic boronates and β-borylallylsilane scaffolds have been realized, respectively. Furthermore, we have studied the asymmetric synthesis of β-borylallylsilane with ee up to81%.Part4:An efficient and practical copper-catalyzed highly regio-and stereoselective borylcupration of internal alkynes with bis(pinacolato)diboron using a catalytic amount of K2CO3as base producing Z-alkenylboron compounds has been demonstrated, avoiding the use of moisture and air-sensitive, relatively expensive NaOt-Bu or KOt-Bu as base.In the appendix, a palladium(O)-catalyzed cascade reaction for the efficient synthesis of2,3-disubstituted benzofuran derivatives containing a3-trisubstituted alkene functional group in moderate yields from alkynyl-substituted benzynes and aryl halides has been discussed.