摘要
Inherently chiral 6,7-diphenyldibenzo[e,g][1,4]diazocine(DDD)has been synthesized enantioselectively for the first time via chiral phosphoric acid(CPA)-catalyzed cyclocondensation of readily available[1,1′-biphenyl]-2,2′-diamine(1a)and benzil(2a)in 82%yield,with 98%ee under mild reaction conditions.The strategy could also be applied to racemic biaryl diamines through kinetic resolution.The unexpectedly high interconversion energy barriers between the enantiomers(ΔG=39.5 kcal/mol)and the chemical stability rendered DDD an ideal platform for developing new chiral ligands and catalysts.Unique inherently chiralDDD-based phosphoramidites,phosphoric acid,mono-and diphosphine ligands were prepared from optically pure diphenol derivative DDDOL as a common precursor.Preliminary asymmetric reactions catalyzed by Pd or Rh in the presence of newly developed ligands exhibited comparable or even better enantioselectivities than the corresponding BINOLor SPINOL-derived ligands.Density functional theory calculation revealed the origin of the enantioselectivity during the process.
基金
the National Natural Science Foundation of China(grant nos.21871268 and 22071250)
the Natural Science Foundation of Guangdong Province of China(grant no.2020A1515011428)
the“BAGUI Scholar”Program of Guangxi Province of China,and the SKLRD Project(grant no.SKLRD-Z-202014)for financial support.
