Activation And Transformation Of C-S,C-O And C-H Bonds

This thesis focuses on activation and transformation of aromatic C-S bonds,alcohol C-O bonds and aromatic C-H bonds.We performed C-S bond cleavage of alkyl aryl sulfoxide,C-S bond cleavage of aryl mercaptans and C-O cleavage of benzyl alochol in the presence of nickel catalysis.We also achieved C-H bond cleavage of quinoline N-oxide and 2-phenylpridine N-oxide under transition metal free conditions.Chapter 1 describes NiBr2(PEt3)2-catalyzed cross-coupling of alklyl aryl sulfoxides with silylzinc reagents.The reaction was performed under mild conditions.Nitrogen-,oxygen-,and sulfur-containing aromatic heterocycles and functional groups such as OMe?F?CF3?COOMe?PhC(O)?CH3C(O)?CH3C(O)NH?C(O)NEt2 groups can be tolerated.Preliminary mechanistic studies show that the reaction might proceed via a Ni(O)/Ni(?)catalytic cycle.Chapter 2 introduces the cross-coupling of aryl mercaptans with silylzinc reagents via NiF2/PCy3 system.This catalyst system can effectively catalyze the reaction of various aryl mercaptans with silylzinc reagents,thus realizing the transformation of C-S bond to C-Si bond.The method performs a wide range of substates.Aryl mercaptans containing electron-withdraw groups,electron-donating and hetercycles were suitable for this transformation and obtained in medium to excellent yields.The yield is decreases with the increase amount of phenyl groups.The reaction might proceed through a Ni(0)/Ni(II)cycle process.Chapter 3 presents the cross-coupling of methyldiarylphosphine oxides or dialkyl methylphosphinates with alcohols in the presence of Ni(COD)2/IMes or Ni(COD)2/PPh3.Through the reaction a series of phosphorus-containing compounds were synthesized.The method tolerates a range of functional groups including OMe,NMe2,SMe,CF3,Cl,F and oxygen-,sulfur-containing hetercycles and obtain the yield above medium.This reaction provides an efficient and green protol to synthesize phosphorus-containing molecules.Mechanistic studies revealed the reaction might proceed via a hydrogen-borrowing process.Chapter 4 reveals metal-free cross-coupling of quinoline N-Oxides and 2-phenyl-pridine N-Oxides with arylzinc reagents.The arylation of quinoline and 2-phenylpyridine was effeciently realized via adding trifluoroacetic anhydride as additive.The reaction demonstrated good compatibility of functional groups.Quinoline N-Oxides and 2-phenyl-pridine N-Oxides inclouding electron-rich and electron-poor groups can be applied in the reaction.Various arylzinc reagents including electron-poor,electron-rich as well as sterically hindered reagents can be used in the conversion.A range of functional groups such as OMe,F,Cl,Br,CF3,C(O)NH2,COOR and NO2 were tolerated.Mechanistic studies showed that the reaction of quinoline N-oxides with arylzinc reagents proceeds via a substitution reaction intermediate and the reaction of pyridine N-oxides with arylzinc reagents proceeds via a ring-opening intermediate.