Expeditious and Stereoselective Synthesis of (1S)‐Spiro[pyran‐4‐quinolines]

• Published in: European journal of organic chemistry 2022-12, Vol.2022 (45), p.n/a
• Main Authors: Chen, Po‐Yen, Chiang, Yi‐Ting, Hsieh, Min‐Tsang, Hseu, You‐Cheng, Lin, Chun‐Hung, Lin, Hui‐Chang
• Format: Article
• Language: English
• Subjects: Alkylation; Aniline; Arylglycoside; exo-Glycal; Friedel−Crafts cyclization; N-Glycosylation; Organic compounds; Quinoline; Stereoselectivity; Substitutes
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.202201116

Spiro[pyran‐4‐quinolines] were synthesized in two steps from exo‐glycals. The first step involved the double additions of aniline (or substituted anilines) to produce C,N‐glycosides. The next step was to eliminate the anomeric N‐aryl group by formation of benzophenone‐derived imine, followed by in situ intramolecular Friedel−Crafts alkylation. The resulting (1S)‐spiro[pyran‐4‐quinolines] were obtained in 60–72 % overall yields with exclusive (from the reactions of exo‐galactals) or high stereoselectivity (from those of exo‐glucals with m‐substituted anilines), respectively. Additionally, exo‐galactals were found suitable to perform the two steps consecutively in one‐pot at 75 °C. Spiro[pyran‐4‐quinolines] were synthesized in two steps from exo‐glycals. The two steps could be performed consecutively in one‐pot manner at 75 °C, leading to formation of (1S)‐spiro[pyran‐4‐quinolines] in 60–72 % overall yields with exclusive stereoselectivity (from the reactions of exo‐galactals). A plausible mechanism was proposed to explain how the products were generated in a stereoselective manner.