Synthesis of Xanthones via Copper(II)-Catalyzed Dehydrogenative Cyclization and Successive Aromatization in a One-Step Sequence

Abstract

In this study, an unprecedented approach to the xanthone scaffold from cyclohexyl(2-hydroxyphenyl)methanone via dehydrogenative cyclization and a successive aromatization cascade is reported. This methodology affords a novel route to the privileged structure with a wide substrate scope (a total of 29 compounds, ≤96% yield) in a highly atom-economic manner.

Application of the Heck Reaction for the Synthesis of C-Glycosyl Phenolic Compounds

“…1 H NMR (500.13 MHz, CDCl 3 ):  = 8.33 (dt, J = 7.5, 1.5 Hz, 2 H, H-8, H-1), 8.20 (dd, J = 7.5, 1.5 Hz, 1 H, H-3), 7.78 (ddd, J = 8.3, 7.5, 1.5 Hz, 1 H, H-6), 7.64 (dd, J = 8.3, 0.8 Hz, 1 H, H-5), 7.43 (ddd, J = 8.3, 7.5, 0.8 Hz, 1 H, H-7), 7.15 (t, J = 7.5 Hz, 1 H, H-2). 13 36 White solid; yield: 101 mg (27%); mp 137-138 °C. 1 H NMR (300.13 MHz, CDCl 3 ):  = 8.33 (dt, J = 7.9, 0.7 Hz, 1 H, H-8), 8.02 (dd, J = 8.4, 1.4 Hz, 1 H, H-1), 7.36-7.44 (m, 1 H, H-7), 7.48 (br d, J = 10.9 Hz, 1 H, H-5), 7.65-7.80 (m, 2 H, H-2, H-6), 7.94 (t, J = 1.4 Hz, 1 H, H-4),.…”

Copper‐Catalyzed Intramolecular SEAr Reaction–Oxidation under Aerobic Conditions: Synthesis of Styryl‐/Alkenyl‐Substituted Xanthone Derivatives

“…[16] Very recently, in 2022, Lim, Kim and co-workers reported a copper-catalyzed dehydrogenative cyclization and aromatization for the synthesis xanthone derivatives www.eurjoc.org (Scheme 1b). [17] Although these methods are interesting, they suffer from the use of expensive transition metals/ligands, excess amounts of oxidants, harsh reaction conditions, and long reaction times. [2] We envisioned to develop an external oxidantfree, metal-catalyzed intramolecular S E Ar reaction-oxidation strategy for the synthesis of xanthone derivatives.…”

“…Next, we reduced the reaction time from 24 h to 12 h to obtain 2 a in similar yield (Table1, entries 11 vs 14). It must be mentioned that Brønsted acids such as PTSA or TfOH provided lower yields of the products even by using the stoichiometric amounts of the acids (Table1, entries[15][16][17]. A control experiment highlighted the importance of the Cu(OTf) 2 catalyst for this protocol, since no product 2 a was obtained in the absence of the catalyst (Table1, entry 18).…”