Ruthenium-catalyzed Synthesis Of Benzimidazoles By Reaction Of O-Nitroanilines With Alcohols And Alkylation Of Methylazaarenes With Alcohols

Transfer hydrogenation(TH)using alcohol as substrate is used widely in organic synthesis,fine chemicals and pharmaceuticals synthesis.Compared with the traditional hydrogenation strategy,transfer hydrogenation using alcohols as alkylating agents have attracted much attention due to that alcohols were easier to handle,generally less toxic and more readily available,process is atom-efficient,greener and only water as a byproduct.In this thesis,we deliberately designed and synthesized Ru(II)complexes of NNN ligand,which displayed high catalytic activity toward the hydrogen-transfer reaction of o-nitroanilines with primary alcohols under solvent-free conditions to produce 2-substituted benzimidazoles.In the absence of any additional ligands,RuCl3 efficiently catalyzed the alkylation of methylquinolines,methylpyridines,2-methyl-benzooxazoles,and 2-methyl-quinoxalines with alkyl-or aryl-alcohols as alkylating agents.This dissertation mainly focused on:1.Reaction of Ru(PPh3)3Cl2 with 2,2'-(1H-pyrazole-l,3-diyl)dipyridine(2,2'-pypzpy)under different conditions yielded two complexes,[(2,2'-pypzpy)Ru(PPh3)2Cl]Cl(1)and[(2,2'-pypzpy)Ru(PPh3)Cl2](2),respectively.Complexes 1 and 2 were characterized by NMR,EA,IR and X-ray crystallographic determinations.They have been used as an efficient catalyst for the synthesis of 2-substituted benzimidazoles via cross-coupling reaction strategy from nitroanilines and alcohols.The advantages of this method are ligand-free,low catalyst loadings and mild reaction conditions.2.Simple RuCl3 salt was found to be an efficient catalyst for the alkylation of methylazaarenes with alcohols without extra organic ligands.Various benzylic and aliphatic alcohols can be used as the alkylating agent and this simple catalytic system also promotes the a-alkylation of methylpyridines,2-methyl-benzooxazole and 2-methyl-quinoxaline.The mechanistic study indicated the alkylation reaction underwent a stepwise transfer hydrogenation,aldol condensation,and hydrogenation reaction pathway.