Rhodium-catalyzed Aza-benzo Down Of Norbornene Piperazines Nucleophiles Asymmetric Ring Opening Reaction

The recent progress in rhodium-catalyzed asymmetric ring opening (ARO) reactions of azabenzonorbornadienes is reviewed. According to a lot of references, We have developed an asymmetric ring opening reaction of azabenzonorbornadienes with substituted piperazine nucleophiles. Under the reaction conditions ([Rh(COD)Cl]₂, bidentate phosphine ligands, THF, reflux), the reaction products (2a)～(2n) were obtained.Oxabenzonorbornadiene (1a) and azabenzonorbornadienes (1b) have been prepared by [4+2] cycloadditions between benzyne (made of anthranilic acid and amylnitrite) and furan or N-Boc pyrrole in the solvent of DME. Then we focused on the development of the rhodium-catalyzed asymmetric ring opening reaction of azabenzonorbornadiene with substituted piperazine nucleophiles. Forteen ring opening products were synthesized and the structures were identified by IR, MS, ¹H NMR, ¹³C NMR and elemental analysis.The reaction conditions of asymmetric ring opening reactions, such as solvents, catalysts loading, reaction temperatures and reaction times were discussed.