Studies On Transition Metal Mediated And Metal-free-heated Procedure To Construct The C-O,B-N,C-B,C-N Bonds

During the past decades researches focused on 1,2-dicarba-closo-dodecaborane derivatives have attracted tremendous attentions due to their special three-dimensional cage structure,high electron-deficiency,and a variety of potential applications in catalyses,materials,energy,medicines,and so on.Among them,more reports are concerning the synthesis,reactivity and the B(3)-H or B(6)-H activation of complexes bearing 1-monothiolato or 1,2-dithiolato-1,2-dicarba-dodecaborane ligands.On the other hand,considering Aryl-or Alkyl-thiolato ligands which have been explored for more applications in the chemical mimic of the hydrogenase enzymes,it is of great mean to explore the viability of the carborane-thiolato ligands in the related areas.Although catalysis directed synthetic chemistry is entering its period of great prosperity,the chemical modifications of carborane always stop on the equivalent synthesis.Recently,some transition metal catalyzed synthetic methodology for constructing the C-C bonds of 1,2-dicarba-dodecaborane have been reported,but there are no reports on using synthetic methods for the functionalization of more B-H bonds in carborane.So we want to develop some transition metal-catalyzed methods to study it.In 2006,D.W.Stephan reported that the frustrated lewis pairs could cleavage the H-H bond in Science(314,1124).After that,the reactivity and catalytic application of frustrated lewis pairs are gradually developed.Amone them,the anions always focus on B(C6F5)3 or its derivatives.We try to replace the anion with nido-carborane anions and study the different reactivity of these new lewis pairs.With the deep insight of our groups' understanding on the B-H bond functionalization,we try to study some small boranes,using the synthetic methods to synthesize the organic boric acid intermediates and also taking the tandem reaction to afford target products in one pot.To be continued,in this thesis the study has been focused on the following four aspects:1.Heterolytic H:2 cleavage by Ru(?)o-Carborane-dithiolate Complexes Leading to Replacement of S by O in the dithiolate Ligand.A sulfide-bridged carborane-ruthenium(?)complex 2-1 clevaged the H-H bond of dihydrogen to generate the intermediate 2-AB.The following step was the exchange of SH(from 2-AB)and OH(forom H2O)in the presence of HBF4-H2O to generate 2-3 containing mixed S/O chelating ligands.The unsaturated Ru(?)centre complexs 2-1 and 2-3 could be oxidized to afford 2-2 and 2-4,respectively.At last,we succeeded in affording two complexes 2-3 and 2-4 with mixed S/O chelating ligands,using NMR and other test facilities to characterize these four complexes and giving a possible mechanism of the transformation from 2-1 to 2-3.2.Transition metal catalyed B-H and N-H double bonds activation to construct the B-N formationAn efficient Ru(OTf)2(COD)-catalyzed synthesis of cage B-N functional complexes 3-2a to 3-2j by B-H and N-H double bonds activation was first reported.And the intermediate 3-Ru was isolated and characterized by X-ray.By NMR study,we proposed a possible mechanism of this coupling reaction.We could not afford these B,N coupling compounds by the previous methods,so our method gave new path to synthsize them.We also studied how different substitution at the 2-position or 4-position of the quinoline ring affected this tranformation reaction,and find that the more-hindered substituents at 2-position of quinoline ring afforded lower yields but the electron-withdrawing substrate at 4-position gave few affect on the yields.3.Study the new nido-carborane anion lewis pairs reactivityThe new nido-carborane anion lewis pairs compounds 4-2a containing cage B?N were synthesized by heating the 4-1a in the refluxed solvent,but we could not afford the 4-2b taking 4-lb as starting material in the same condition due to the two more-hindered t-Bu group.4-lb compound reacted with carbodiimides well as frustrated lewis pairs to generate two new nido-carborane guanidines 4-2c and 4-2d.By the X-ray analysis of them,C=N double bonds were cleavaged and the B-H bonds of nido-carborane occured a hydroboration reaction as BH3,not leaving H2 with H+ of cation.Considering this special reaction,some control experiments were taken to prove the mechanism.During that,we first isolated a cation 4-2e,which was always proved the hydrolysis of carbodiimide.With the experiments and previous reports,we proposed a possible mechanism with the formation of 4-2c and 4-2d.4.Amino-Directed Rh?-Catalyzed C-H Activation Leading to One-Pot Synthesis of N-H CarbazolesHerein,we reported that N-H carbazoles could be directly obtained from non-protected 2-aminobiaryl starting compounds through the use of tandem[Cp*Rh(OTf)2]/Cu(OAc)2(Cp*= pentamethylcyclopentadienyl)mediation in a one-pot reaction via a reactive C-H borylated intermediate 5-2a.This catalytic system could potentially be used for the synthesis of biologically active natural products and we afforded a better yield.The low yields of the stepwise borylation to 2a might be attributed to the excess distribution of the NH2 groups of the 2-aminobiaryl substrates around the catalyst preventing the metal from efficiently activating the C-H bond.It is worth mentioning that amine-group-directed C(sp2)-H oxidative activation from alkylamines and arylamide has been reported,but free aryl-aminodirected C-H activation remains more elusive.It had some advantages over previously reported examples by using a low loading of noble metal catalyst(Rh<0.5%)and inexpensive Cu(OAc)2,thus it could be proved potentially useful for the synthesis of medically important compounds.