Chiral Phosphoric Acid-Catalyzed Pictet–Spengler Reactions for Synthesis of 5′,11′-Dihydrospiro[indoline-3,6′-indolo[3,2‑c]qui-nolin]-2-ones Containing Quaternary Stereocenters
journal contributionposted on 13.04.2021, 07:03 by Xin-Wei Wang, Xiang Li, Mu-Wang Chen, Bo Wu, Yong-Gui Zhou
Chiral phosphoric acid-catalyzed Pictet–Spengler reactions of 2-(1H-indolyl)aniline derivatives and isatins by the condensation/cyclization process have been realized. A series of enantioenriched 5′,11′-dihydrospiro[indoline-3,6′-indolo[3,2-c]quinolin]-2-ones bearing quaternary stereogenic centers were obtained with excellent yields and up to >99% ee. This protocol was suitable for the Pictet–Spengler reactions of 2-(1-benzyl-5-methyl-1H-pyrrol-2-yl)aniline, and a variety of 1′,5′-dihydro-spiro[indoline-3,4′-pyrrolo[3,2-c]quinolin]-2-ones could also be obtained in good yields and up to 88% ee.