Acid-catalysed rearrangements. Specific syntheses of 2,3-disubstituted indoles and N-hydroxyindoles

Abstract

Diastereoisomeric 2-alkyl-(or phenyl)-2-phenyl-3-hydroxy-2,3-dihydroindoles in an acid medium undergo elimination of water and transposition of the group having the major migratory power from C-2 to C-3. The stereochemistry of these compounds and the substituent at the nitrogen atom does not affect the final products, which are the same for the two diastereoisomeric indolines. The migratory power follows the sequence benzyl > phenyl > alkyl. The resulting 2,3-disubstituted indoles and N-hydroxyindoles were obtained in quantitative yield.