Pd-catalyzed C3-selective Arylation Of Pyridines With Phenyl Tosylates

Pyridine compounds are very important fine chemical materials with high addedvalue, pyridine compounds are widely used in pesticides, pharmaceuticals, dyes,spices, feed additives, rubber chemicals, food additives, surfactants, viscosity cakingagent, synthetic materials and other industries.transition metal catalyzed crosscoupling reaction is one of the most effective methods for synthesis of pyridinecompounds. Compared to conventional coupling reactions, transition metal catalyzedC-H activation is a very efficient way for synthesizing of pyridine compounds, theadvantage of this reaction is that there is no need for the use ofprefunctionalizedprepared through such as metallization or halogenations.After investigating the literature, we believe that3-arylpyridine compounds canbe achieved by reaction of pyridine with phenyl tosylates through C3-H activation ofpyridine.This paper described C3-selective arylation of pyridines with phenyl tosylates.The major work and results are listed as following.(1) The author summarized the recent developments of transition metalcatalyzed C-H activationswith the emphasis on non-oriented C-H activation.(2) After examining various reaction conditions including catalyst, ligands,reaction temperature, base, solvent, the optimized reaction conditions for synthesis of3-arylpyridine from pyridine and phenyl tosylates can be established as:1equiv ofphenyl tosylates,10mol%Pd(OAc)2as catalyst,30mol%1,10-Phenanthrolinemonohydrate as ligand,3equiv of Cs2CO3as base,3ml of pyridine as solvent,150oCfor48hours under nitrogen. Various3-arylpyridine compounds can be obtained inhigh yields with this protocol. Based on literature and previous resultsobtained in thelaboratory, a possible mechanism was proposed to explain the reaction mechanism.(3) we have also developed a method for the synthesis4-naphthalenylmethylpyridine:1equiv of phenyl tosylates,15mol%Pd(OAc)2ascatalyst,45mol%1,10-Phenanthroline monohydrate as ligand,3equiv of Cs2CO3asbase,3ml of4-methylpyridine as solvent,150oC for48hours under nitrogen. Various4-naphthalenylmethylpyridine compounds can be synthesized in high yields with thisprotocol. Notably, we found that the reaction can also occur when bromonaphthaleneswere used as a substrate. Based on literature and previous resultsobtained in thelaboratory, a possible mechanism was proposed to explain the reaction mechanism.