Transannulation Of N-Sulfonyl-1,2,3-Triazole With Nitriles Promoted By BF₃·Et₂O

Metal-carbene is an important intermediate in the field of organic synthesis.The transition metal catalyzed decomposition of diazo compounds is an important way to obtain metal-carbene.However,the instability and potential danger of diazonium compounds greatly limited their application.With the rapid development of metal rhodium carbene initially developed by Teyssie via rhodium acetate,instead of copper catalyst,catalyzed decomposition of diazo compoumds and great achievement of"click chemistry",N-sulfonyl-1,2,3-triazole,which could undergo a tautomerism to form a diazoimine compound can be used as carbene precursor,and in the presence of transition metal catalyst,?-imine metal carbene intermediate could be generated.?-Imine metal carbene bears great reaction diversity,such as:1,2-migration,cyclopropanation,coupling reactions,ylide formation,insertion reactions;and intra-and intermolecular reaction modes brings additional flexibility for the transformation of?-imine metal carbene.However,it has not been realized the Lewis acid promotes the ring opening of N-sulfonyl-1,2,3-triazole to give the carbene intermediate.So here,in this thesis,the first metal-free BF₃·Et₂O promoted transannulation of N-sulfonyl-1,2,3-triazole with nitrile compounds was accomplished.After the optimization of the reaction conditions,it was found that under nitrogen atmosphere,nitrile?0.1 M?was used as a solvent,and the reaction was carried out under reflux conditions for about 2 hours,N-sulfonyl-1,2,3-triazole could be converted to the corresponding imidazole derivatives under the promotion of 1.0 equiv BF₃·Et₂O in up to 99%yield.At the same time,the reaction could avoid side reactions such as desulfonation reaction and fluorination reaction.The product could be desulfonylated delivering 1H-imidazole compound in a quantitative yield by concentrated hydrochloric acid,and the reaction was also successfully employed in the later modification of bioactive molecules.