The acylation of racemic 2-methyl-1,2,3,4-tetrahydroquinoline and 2-methylindoline by (S)-naproxen acyl chloride resulted in their kinetic resolution with the predominant formation of (S,S)-diastereoisomeric amides (de 78–76%), recrystallisation of which followed by acid hydrolysis gave individual (S)-isomers of heterocyclic amines.