Catalyzed Oxa-benzo Down The Norbornene Piperazine Nucleophiles Asymmetric Ring Opening Reaction

In this paper, the recent progress in transition metal-catalyzedasymmetric ring opening (ARO) reactions of oxabenzonorbornadienes isreviewed. According to a lot of materials, We have developed anasymmetric ring opening reaction of oxabenzonorbornadienes withpiperazine derivatives nucleophiles. Under the reaction conditions([Rh(COD)Cl]₂, bidentate phosphine ligands, THF, reflux), the reactionproducts (2a)-(2l) were obtained.At the fifty degree centigrate, oxabenzonorbornadienes (1a) has beenprepared by [4+2] reactions between o-aminobenzoic acid and furan inthe presence of DME and Amylnitrite. Added piperazine derivativesnucleophiles, intermediate (1a) was led to asymmetric ring openingreactions under rhodium catalysts and chiral biphosphine ligands inboiling. The structure of target compounds (2a)-(2l) were confirmed byIR, MS, ¹H NMR, ¹³C NMR and Elemental Analysis. Otherwise theoptical purity of the target compounds were measured. We have culturedsingle crystal for some compounds and detected the spatial configurationby X-ray diffraction.In this paper, the reaction conditions of asymmetric ring openingreaction conditions, such as solvent, catalyst, reaction temperature andtime were discussed.