| The formation of C-C and C-X bond is a key component of organic chemistry.Traditional coupling reactions are efficient and powerful methods for C-C and C-X bond formation.These approaches generally require environmentally harmful strong acid/alkali,alkyl halides and/or inorganic oxidants.Compared with these transformations,the transfer hydrogenations use cheaper,less toxic alcohols as the alkylating agents and release water(and H2)as the by-product(s),which could avoid the use of potentially hazardous reagents and the formation of salt wastes.In recent decades,transition catalysts bearing various toxic phosphine ligands displayed high catalytic activity towards the construction of C-C and C-X bonds.Transition metal complexes with pyrazolate or thiolate ligands,however,have less been explored in transfer hydrogenation.In this thesis,a series of bifunctional copper and ruthenium complexes were synthesized and their catalytic activities of transfer hydrogenations have been explored.The results are mainly described as follows:1.Bifunctional Cu(I)N-heterocycle thiolate clusters[Cu3(pymt)3]n(1a,Hpymt=pyrimidine-2-thiol)and[Cu6(L)6](L=4,6-dimethylpyrimidine-2-thione(1b)),2-benzothiazolethiol(1c),1H-pyridine-2-thione(1d))display high catalytic activity toward the following reactions:(i)Acceptorless dehydrogenation of alcohols:Cu(I)N-heterocycle thiolate clusters1a-1d efficiently catalyze the acceptorless dehydrogenation of a variety of secondary/primary benzylic,allylic,and aliphatic alcohols to the corresponding ketones and aldehydes in high yields of isolated products upon release of H2.(ii)Chemoselective transfer hydrogenations of unsaturated carbonyls:Using n-BuOH as solvent and the hydrogen source,equimolar K2CO3 as base,1a-1d catalyzeα,β-unsaturated ketones to saturated ketones with high catalytic activity and selectivity.The chemoselectivity are controlled by the concentration of Cu(I)monohydride and protonated Cu(I)hydride complexes in the catalytic system.(iii)Cross-coupling of secondary and primary alcohols:Complexes 1a-1d could efficiently catalyze the cross-coupling of secondary and primary alcohols to giveα-alkylated ketones.This catalytic system is also suitable for the synthesis of pyridines and quinolines by the cross-coupling annulation ofγ-amino alcohols and 2-aminobenzyl alcohols with secondary alcohols.The metal-ligand bifunctional catalysis is essential for the high activity and selectivity.2.Reactions of pincer ligands 2-(3-R-1H-pyrazol-1-yl)-6-(1H-pyrazol-3-yl)pyridine(pz~RpypzH,R=C6H5,4-MeOC6H4,4-CF3C6H4)with RuCl2(PPh3)3 produce three Ru(II)complexes[RuCl2(pz~RpypzH)(PPh3)](R=C6H5(1e),4-MeOC6H4(1f),4-CF3C6H4(1g)).Furthermore,mixture of 1e-1g with MeCN in CH2Cl2 yield ionic Ru(II)complexes[RuCl(pz~RpypzH)(PPh3)(MeCN)]Cl(R=C6H5(1h),4-MeOC6H4(1i),4-CF3C6H4(1j)).1h-1j could catalyze the coupling of arylacetonitriles and primary alcohols,givingα-alkylated alkylnitriles in high yields.The metal-ligand bifunctional catalysis,substituent groups on ligand and coordination geometry of Ru center have a significant influence on the catalytic activity and selectivity.3.Reactions of a pincer ligand 2-(1H-pyrazol-1-yl)-6-(1H-pyrazol-3-yl)pyridine(pzpypzH)with Cu(NO3)2,Cu(ClO4)2,CuSO4,CuCl2 or CuI produce three dinuclear Cu(II)complexes[{Cu(NO3)}(μ-pzpypz)]2(1k),[{Cu(ClO4)}(μ-pzpypz)]2(1o),[Cu2(μ-SO4)(μ-pzpypz)2]·2MeOH(1m·2MeOH),one mononuclear Cu(II)complex[CuCl2(pzpypzH)](1n)andonetrinuclearCu(I)/Cu(II)complex[(ICu)(μ-I)2Cu2(μ-pzpypz)2](1o),respectively.Complexes 1k–1o display high catalytic activity toward the ammoxidation of alcohols to nitriles and the aerobic oxidation of alcohols to aldehydes in H2O.4.Without using any additional ligands,RuCl3 efficiently catalyze the reductive N-alkylation of aryl nitro compounds with alcohols using bio-based glycerol as the hydrogen source and without the need for any added solvents.The reaction could be easily manipulated to provide imine or amine cleanly and in high yield. |
