Chiral Phosphoric Acid-Catalyzed Pictet–Spengler Reactions for Synthesis of 5′,11′-Dihydrospiro[indoline-3,6′-indolo[3,2-<i>c</i>]qui-nolin]-2-ones Containing Quaternary Stereocenters

Abstract

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.

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