A new route to naphtho[2,3-b]furan-4,9-diones from thio-substituted 1,4-naphthoquinones

Abstract

Bromine 4 equiv. 2 equiv. 2 equiv. 3 equiv. 4 equiv. 3 equiv. 6 equiv. 4 equiv. 2 equiv. 5 equiv. Time 3.5 h 30 rnin 40 min 30 min 30 rnin 30 min 10 min 15 min 1.5 h 2 h Yield (%) 75 51 46 86 46 46 50 46 97 64 Paper 9/01 877H

Transition-Metal-Free One-Pot Synthesis of Naphthoquinonefuran Derivatives Through Sequential Nucleophilic Substitution–Nucleophilic Addition Reaction

“…Yield, 58% (35.8 mg, Eluent: EtOAc/petroleum ether = 1/5); red solid, mp 276–278 °C (lit . mp 276–277.5 °C); 1 H NMR (500 MHz, CDCl 3 ) δ8.17 (d, J = 6.2 Hz, 1H), 8.13 (d, J = 6.4 Hz, 1H), 7.76 (d, J = 8.2 Hz, 2H), 7.72–7.67 (m, 2H), 7.40 (d, J = 8.2 Hz, 2H), 7.11 (s, 1H).…”

“…Yield, 52% (33.7 mg, Eluent: EtOAc/petroleum ether = 1/5); brown solid, mp 299–302 °C (lit . mp 300–301 °C); 1 H NMR (500 MHz, CDCl 3 ) δ 8.27–8.25 (m, 1H), 8.22–8.20 (m, 1H), 7.90 (s, 1H), 7.81–7.75 (m, 3H), 7.48–7.41 (m, 2H), 7.23 (s, 1H).…”

“…Yield, 58% (35.9 mg, Eluent: EtOAc/petroleum ether = 1/5); orange solid, mp 185–187 °C (lit . mp 185–186 °C); 1 H NMR (500 MHz, CDCl 3 ) δ 8.20–8.17 (m, 1H), 8.16–8.14 (m, 1H), 8.04 (dd, J = 7.8, 1.7 Hz, 1H), 7.73–7.69 (m, 2H), 7.62 (s, 1H), 7.46 (dd, J = 7.8, 1.3 Hz, 1H), 7.37–7.29 (m, 2H).…”

“…The wide spectrum of biological activities has attracted widespread interest in the field of medicinal chemistry; therefore, much effort has been focused on the synthetic methods of naphthofuroquinone derivatives. Over the past decades, base-catalyzed, bromine-mediated, different annulations − (such as thermal cyclization, photoaddition, oxidative cycloaddition, Diels–Alder cycloaddition/aromatization, oxidative cyclization/isomerization), one-pot cascades, and transition-metal-catalyzed syntheses of the naphthofuroquinone skeleton have been reported.…”

Palladium(II)-Catalyzed Oxidative Annulation of 2-Hydroxynaphthalene-1,4-diones and Internal Alkynes via C–H Functionalization

“…Mainly starting from 2-hydroxy-1,4-naphthoquinones, the multicomponent reaction (Scheme a), various [3+2] annulation strategies [thermal cyclization with enamines (Scheme b), CAN-mediated oxidative cycloaddition with vinyl sulfide and enol ether (Scheme c), photoaddition (Scheme d)], one-pot cascade procedure (Scheme e), and transition-metal-catalyzed methods (Scheme f,g) have been developed. In addition, other miscellaneous methods such as Diels–Alder cycloaddition/aromatization, oxidative cyclization/isomerization, Friedel–Crafts acylation/oxidation, base-promoted oxidative coupling of 2-hydroxy-1,4-naphthoquinones with (Z)-2-ylideneimidazo­[1,2- a ]­pyridin-3­(2 H )-ones, and bromine-mediated intramolecular cyclization have also been developed. Despite the significant progress made in the synthesis of furonaphthoquinones, novel synthetic approaches with milder reaction conditions and enhanced reaction efficiency are still desirable.…”