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

Abstract

An efficient Pd­(II)-catalyzed oxidative annulation of 2-hydroxynaphthalene-1,4-diones and internal alkynes has been developed with high step efficiency. A broad range of functional groups are compatible with this reaction, thus providing a new entry to diverse naphtho­[2,3-b]­furan-4,9-dione derivatives in good to high yields.

Rhodium(III)-Catalyzed C–H/N–H Alkyne Annulation of Nonsymmetric 2-Aryl (Benz)imidazole Derivatives: Photophysical and Mechanistic Insights

“…Hence, CoCp*­(CO)­I 2 and Pd­(OAc) 2 (entries 2 and 3) were also evaluated, albeit with no success. Aware of the ability of palladium-based catalysts to mediate annulation reactions, we also tried three different palladium­(II) complexes prepared by our research group, herein named Pd-Complex A , Pd-Complex B , and Pd-Complex C , but, unfortunately, the product formation was not observed (entries 4–6). Finally, we also tested [Ir­(1,5-cod)­Cl] 2 /AgOAc as a catalyst system and the desired product was obtained in only 26% yield (entry 7).…”

The Different Facets of Metal‐Catalyzed C−H Functionalization Involving Quinone Compounds

“…Sun et al . have used 2‐hydroxynaphthoquinones for the synthesis of furonaphthoquinones through oxidative annulation of internal alkynes [79] . Multiple possible mechanisms were offered; base‐assisted insertion of Pd(II) into the quinoidal C−H bond might be followed by migratory insertion of an alkyne and reductive elimination.…”

An Efficient Synthesis of Naphtho[2,3-b]furan-4,9-diones via Visible-Light-Mediated [3+2] Cycloaddition Reaction

“…In recent years, different methodologies for the synthesis of furonaphthoquinones have been reported ( Scheme 2 ). Predominantly starting from 2-hydroxy-1,4-naphthoquinones, the two-step procedures, such as multi-component reaction ( Scheme 2 a) [ 16 ], thermal cyclization with enamines ( Scheme 2 b) [ 17 ], and CAN-mediated oxidative cycloaddition with enol ether ( Scheme 2 c), [ 18 ] and one-step cascade approaches, such as transition-metal ( Scheme 2 d) [ 19 ] or strong-base ( Scheme 2 e) [ 20 ] or strong oxidant ( Scheme 2 f) [ 21 ] promoted thermal cyclization methods have been developed. In addition, other multifarious methods, such as Friedel−Crafts acylation/oxidation [ 22 ] and bromine-mediated intramolecular cyclization [ 23 ], have also been developed.…”