Boroles are five-membered,unsaturated heterocycles with an antiaromatic 4π-electron BC_4 ring.According to Breslow’s exten sion of the H(u|¨)ckel rule,the intrinsic antiaromaticity can be attrib uted to the unfavorableπ-electron delocalization of the BC_4 core,in which a vacant p-orbital on boron mediates the conjugation of four ringπ-electrons.The first borole derivative,1,2,3,4,5-pentaphenylborole[PhBC_4Ph_4],was isolated by Eisch and Hota[1]in 1969,but its crystal structure has been determined by X-ray crystallography recently[2].Since the structure of borole was confirmed,borole Boroles are five-membered, unsaturated heterocycles with an antiaromatic 4π-electron BC_4 ring. According to Breslow’s extention of the H (u | ¨) ckel rule, the intrinsic antiaromaticity can be attrib uted to the unfavorableπ-electron delocalization of the BC_4 core , in which a vacant p-orbital on boron mediates the conjugation of four ringπ-electrons. the first borole derivative, 1,2,3,4,5-pentaphenylborole [PhBC_4Ph_4], was isolated by Eisch and Hota [1] in 1969 , but its crystal structure has been determined by X-ray crystallography recently [2] .ince the structure of borole was confirmed, borole