Asymmetric induction using chiral 1,2,4-triazole and benzimidazole derivatives

Lithiated N-substituted 1,2,4-triazoles 3 and 8 and benzimidazole 11 reacted with (1R)-fenchone to give derivatives 5c, 9 and 12 in good yields as single diastereoisomers. (S)-Lactic acid 16 reacted with o-phenylenediamine 15 to give optically pure (S)-2-(I-hydroxyethyl)benzimidazole 17 (85%). Ring closures converted the fenchone derivative 12 into novel tricyclic fused benzimidazoles 13 and 14, and converted oxazolidine derivative 17 into compound 18 in yields of 50-70% as single diastereoisomers. Lithiated derivative 18 was alkylated to give compound 19 as a single diastereoisomer in high yield. (C) 1997 Elsevier Science Ltd.