The Synthesis Of NNN’ Pincer Ru(Ⅱ) Complexes And Application In α-alkylation Of Nitriles With Alcohols

This thesis studies the synthesis and characterization of NNN’pincer Ru（II）complexes and explores their applications in a-alkylation of nitriles with alcohols.1.Synthesis and characterization of NNN’pincer Ru（II）complexes（1）2,2’-bipyridine reacted with hydrogen peroxide in trifluoroacetic acid to give2,2’-bipyridine-1-oxide,which was converted into 2,2’-bipyridyl-6-carbonitrile in the presence of trimethylsilyl cyanide and benzoyl chloride.To obtain bipyridyl imidazoline ligands 1a-c,bipyridyl carbonitrile first underwent base-induced hydrolysis in EtOH/H₂O solution to afford 2,2’-bipyridyl-6-carboxylic acid.Also,the desired ligand precursors 1a-c were obtained in 50-56%yields via formation of amido alcohols and subsequent cyclization etc.（Scheme 1）.The new compounds 1a-c were characterized by ¹H NMR,¹³C NMR,IR and HRMS.Scheme 1（2）On the other hand,addition of bipyridyl carbonitrile into a dilution solution of MeONa followed by neutralization with HOAc would provide2,2’-bipyridyl-6-carboxyimidate.The corresponding ligand 1d was then obtained by refluxing bipyridyl carboxyimidate with（1S,2S）-1,2-diphenylethane-1,2-diamine in anhydrous CH₂Cl₂ in 70%yield.Finally,treatment of 1d with aryl sulfonyl chloride in the presence of dimethylaminopyridine（DMAP）furnished the desired bipyridyl imidazolines 1e-i in 91-99%yields（Scheme 2）.The new compounds 1d-i were characterized by ¹H NMR,¹³C NMR,IR and HRMS.Complex 1f and 1g were further confirmed by X-ray single crystal diffraction.Scheme 2（3）The corresponding cyclometaled ruthenium complexes 2a-h was obtained in45-70%yields by reaction of ligand precursors 1a-c and 1e-i with an equimolar amount of RuCl₂（PPh₃）₃ in toluene under reflux condition（Scheme 3）.The new compounds 2a-h were characterized by ¹H NMR,¹³C NMR,³¹P NMR,IR,HRMS and EA.Complex 2a were further confirmed by X-ray single crystal diffraction.Scheme 32.Application of NNN’pincer Ru（II）complexes in a-alkylation of nitriles with alcohols.Initially,the a-alkylation of 4-bromobenzyl cyanide with benzyl alcohol was selected as the model reaction to examine the catalytic activity of Ru complexes 2a-h.The experimental results showed that complex 2h exhibited the best catalytic effect in the reaction.Under the condition of 1.5 mol%2h as catalyst,0.15 equiv.KOH as base and toluene as solvent,the products were isolated in up to 97%yield at 140 ^oC for 4 h（Scheme 4）.Scheme 4...