Synthesis and Characterization of 1‑Hydroxy-4,5-arene-Fused Tropylium Derivatives

• Published in: Journal of organic chemistry Vol. 86; no. 19; pp. 13800 - 13807
• Main Authors: Kodama, Takuya, Kawashima, Yuki, Uchida, Kenta, Deng, Zhirong, Tobisu, Mamoru
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 01.10.2021; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; organic chemistry; Physical Sciences; protonation; Science & Technology; X-ray diffraction; MOLECULAR-STRUCTURE; PSEUDOAROMATIC COMPOUNDS; STRUCTURAL CHEMISTRY; MAGNETIC-RESONANCE SPECTRA; BENZOTROPONE SYSTEM; DIE DIPOLMOMENTE; BENZTROPYLIUM-REIHE; AROMATIC CHARACTER; CONDENSATION PRODUCTS; INDEPENDENT CHEMICAL-SHIFTS
• ISSN: 0022-3263; 1520-6904; 1520-6904
• DOI: 10.1021/acs.joc.1c01818

The properties of 1-hydroxy-4,5-arene-fused tropyliums were assessed based on experimental and theoretical investigations. An X-ray crystallographic analysis revealed a decrease of bond alternation in the seven-membered ring of 1-hydroxy-4,5-benzotropylium derivatives compared with that of the parent 4,5-benzotropones, which is indicative of an increase in aromaticity upon protonation. NICS and AICD calculations also supported the increased aromaticity of 1-hydroxy-4,5-arene-fused tropylium. The pK a values for a series of 1-hydroxy-4,5-arene-fused tropylium derivatives were also determined.