Mn‐Mediated Radical Cascade Cyclization of 1,6‐Enynes with Arylboronic Acids to Access Dihydrobenzo[b]fluorenones

Abstract

Herein, we report the synthesis of functionalized dihydro-benzo[b]fluorenones through a manganese-mediated cascade radical cyclization of β-alkynyl propenones [1,6-enynes] with arylboronic acids. In the present strategy, the in-situ generated aryl radical undergoes chemo-selective addition followed by 5exo-trig cyclization. The reaction is emphasized by high atom-and step-economy with the construction of three new CÀ C bonds to access the dihydrobenzo[b]fluorenones in 68-81% yield under mild reaction conditions. The synthetic efficacy of the developed method is evidenced by the construction of new CÀ C and CÀ N bonds.

Carbonylative cyclization of biaryl enones with aldehydes and oxamic acids

“…5 b Recently, we have developed a visible light-promoted thiolative/sulfonylative radical cascade annulation to access thio-functionalized phenanthrenones. 5 c In continuation of our work on radical-mediated annulations, 6 herein we report the carbonylative annulation of biaryl enones using aldehyde/oxamic acids as the radical sources (Scheme 1c). Traditionally, acyl/benzoyl radicals are generated using keto acids or acyl chlorides in the presence of metal catalysts.…”

Recent Advances in Cyclization Reactions of 1,6‐Enynes

“…In 2022, the Reddy group disclosed an approach to afford functionalized dihydro‐benzo[ b ]fluorenones through a Mn‐mediated cascade cyclization of 1,6‐enynes with arylboronic acids (Scheme 49). [41] This protocol, which proceeded through a chemo‐selective 5‐ exo ‐trig cyclization, provided access to a class of polycyclic skeletons in good to excellent yields with good functional group compatibility. This method features step‐economy with the construction of three new C=C bonds in the fused polycyclic product.…”

A Domino Dearomative ipso-Annulation/Desymmetrization Approach: Stereoselective Access to Tricyclic Alkaloid Skeletons

“…As part of our ongoing projects on ipso -annulations and aiming toward the generation of polycyclic skeletons, we envisioned a domino process that installs the functionality promoting the dearomative ipso -cyclization to give spiro-cyclohexadienone, where the same installed group would also mediate the desymmetrization reaction to construct a tricyclic alkaloid framework. To achieve the planned domino reaction sequence, we anticipated that N -benzyl-acrylamides might be appropriate substrates.…”