Reductive Reaction Of Acetophenone Catalyzed By Ruthenium Complex

Reduction of acetophenone was an important reaction in organic systheses. Theproducts of alcohol and amine can be used in pharmaceutical, pesticide, dye and otherindustries. Due to the mild catalytic condition in transfer hydrogenation reaction, rutheniumcomplexes were widely used in reductive reaction. Main researches in the field have beenreviewed in the thesis. Some ligands were synthesized and the catalytic activities inreductive reaction of acephenone have been evaluated. The main results are as follows:Oxazoline ligand (L1) was synthesized using L-phenylalanine and L-alanine as the rawmaterial; Benzenesulfonamide ligand (L2) was synthesized using D-phenylglycinol and4-methyl-benzenesulfonylchloride as the raw material. The catalytic properties of catalystforming in situ from the mixture of oxazoline ligand (L1)、benzenesulfonamide ligand (L2)、phenylglycinol ligand (L3) and glucosamine hydrochloride ligand (L4) with RuCl2(PPh3)3or[RuCl2(p-cymene)]2in transfer hydrogenation of acetophenone evalulated.The catalytic activity of L1/RuCl2(PPh3)3was increasing with increase of temperature.At the ratio of catalyst precursor: ligand: acetophenone=1:1:1000, the conversion ofacetophenone was12%and96%at90℃and140℃for3hours, respectively. The catalyticactivity of L2/RuCl2(PPh3)3was higher than that of L2/[RuCl2(p-cymene)]2.When thesystem of L3/[RuCl2(p-cymene)]2was used as catalyst at the ratio of catalyst precursor:ligand: acetophenone=1:4:2000, the conversion of acetophenone after10hours was92.3%,ee%was25.9%at25℃. At90℃, the conversion of acetophenone after3h was76.5%, theee%was10.3%at the ratio of catalyst precursor: ligand: acetophenone=1:1:800. At140℃and the ratio of catalyst precursor: ligand: acetophenone=1:1:2000, the conversion ofacetophenone after two hours was64.1%, the ee%was1.1%. ee%value was gradualdecline along with extension of reaction time and increase of temperature. When the systemof L4/[RuCl2(p-cymene)]2was used at ratio of catalyst precursor: ligand: acetophenone=1:1:100, the conversions of acetophenone were2.7%and12.4%, ee%were48%and24.2%for12and24hours at25℃,respectively.Under the promotion of the catalysts generated in situ from RuCl2(PPh3)3and α-aminosubstituted benzimidazole derivatives(L5-L8) and pyridine substituted iminazoles (L9-L10),the reductive amination of acetophenone with the ammonium formate generated α-phenylethylamine, N-(1-phenylethyl)formamide and α-phenylethanol. In this reductiveamination reaction, the ammonium formate was the resource of hydrogen and amine. Thebulkier substituent and phenyl group on the imidazole ligand and two pyridine methylsubstituents on NHC ligands will enhance the catalytic activity. At85℃, the reductiveamination of acetophenone was faster, while at125℃, the transfer hydrogenation ofacetophenone to produce α-phenylethanol became the main reaction.