Study On Metal-free C-H Borylation Of Arylpyridine Derivatives

Tetracoordinated organoboron compounds with a?-conjugated N,C-chelate skeletons have been widely used in the field of organic photoelectric materials due to their high thermal stability,excellent luminescent performance,and strong electron affinity.Traditional synthetic methods have some drawbacks such as tedious synthetic routes,participation of toxic and flammable organometallic reagent,and the use of transition metal catalysts,which are inconsistent with the requirements green chemistry and sustainable development.Therefore,it is of great scientific significance to develop a simple and green method for the synthesis of N,C-chelate organoboron compounds.In this dissertation,a novel method for the synthesis of N,C-chealte organoboron compounds via metal-free C-H borylation of arylpyridine derivatives with dibutylboron triflate?TfOBⁿBu₂?is described to afford 2-?2-?dibutylboraneyl?aryl?pyridine derivatives in one step.The metal-free reaction condition,easy operation and post-treatment simplicity are the derivatives of this novel method.The reaction of 2-phenylpyridine with TfOBⁿBu₂ was chosen as a model reaction to optimize the reaction conditions.The additives,solvent,reaction temperature and time were examined and the optimum reaction conditions were obtained as follows:under a in N₂ atmosphere,2-phenylpyridine?77.6 mg,0.5 mmol?and TfOBⁿBu₂?1 M in CH₂Cl₂,0.75 mL,0.75 mmol?as substrates,Et₃N?0.75 mmol?as base,toluene?3mL?as reaction solvent,and reacted in a sealed tube at 80?for 10 h.It was found that desired product 2-?2-?dibutylboraneyl?phenyl?pyridine was obtained in 97%yield under optimal conditions.2-Arylpyridine derivatives,which contain both electron donating groups and withdrawing groups on aromatic moiety,could proceed smoothly to generate the corresponding products in good yields.This synthesis is also suitable for substrates with quinolinyl as directing group.The obtained 2-?2-?dibutylboraneyl?phenyl?pyridine derivatives were characterized by ¹H-NMR,¹³C-NMR,¹¹B-NMR and HRMS?ESI?.