C(sp^(2))-H amination represents an attractive approach for the synthesis of enamines,which is intrinsically associated with the challenge of controlling of stereochemistry and primarily relying on transition-metal ca...C(sp^(2))-H amination represents an attractive approach for the synthesis of enamines,which is intrinsically associated with the challenge of controlling of stereochemistry and primarily relying on transition-metal catalysis.Herein,a metal-free C(sp^(2))-H amination ofα-substituted styrenes has been achieved,leading to stereodivergent formation of both E-and Z-enamines in 50%–97%yield under mild conditions by using PhI(OAc)_(2) as a green oxidant and ortho-phenylenediamines as nitrogen source.Interestingly,the Z/E selectivity can be controlled readily by switching the reaction medium.E-isomers were formed preferentially in THF,whereas n-hexane favored the formation of Z-isomers.Preliminary mechanistic studies suggested that in situ formed ortho-benzoquinone diimides are the key intermediates,and there is a correlation between solvent polarity and stereoselectivity.This study enriches the chemical repertoire of ortho-benzoquinone diimides particularly with respect to sustainable amination.展开更多
基金supported by the National Natural Science Foundation of China(No.22001085)Shandong Provincial Natural Science Foundation(No.ZR2021QB148)+1 种基金Fundamental Research Funds for the Central Universities(No.HUST:2023JCYJ001)Research Institute of Zhejiang Sci-Tech University in Longgang(No.LGYJY2021013)for financial support。
文摘C(sp^(2))-H amination represents an attractive approach for the synthesis of enamines,which is intrinsically associated with the challenge of controlling of stereochemistry and primarily relying on transition-metal catalysis.Herein,a metal-free C(sp^(2))-H amination ofα-substituted styrenes has been achieved,leading to stereodivergent formation of both E-and Z-enamines in 50%–97%yield under mild conditions by using PhI(OAc)_(2) as a green oxidant and ortho-phenylenediamines as nitrogen source.Interestingly,the Z/E selectivity can be controlled readily by switching the reaction medium.E-isomers were formed preferentially in THF,whereas n-hexane favored the formation of Z-isomers.Preliminary mechanistic studies suggested that in situ formed ortho-benzoquinone diimides are the key intermediates,and there is a correlation between solvent polarity and stereoselectivity.This study enriches the chemical repertoire of ortho-benzoquinone diimides particularly with respect to sustainable amination.
