Palladium-Catalyzed Intramolecular Oxidative Arylations for the Synthesis of Fused Biaryl Sulfones

Pd(II)/Lewis Acid Catalyzed Intramolecular Annulation of Indolecarboxamides with Dioxygen through Dual C-H Activation

Transition-metal ion catalyzed intramolecular dual C-H activation to construct polycyclic heteroarene skeletons is merited for its step and atom-economic advantages in organic synthesis. However, in most cases, stoichiometric oxidants, elevated temperature, and other harsh conditions were commonly faced for this reaction, which apparently block the synthetic applications. Herein, we report a Pd(II)/LA (LA: Lewis acid) catalyzed intramolecular dual C-H activation to construct indoloquinolinone derivatives under mild conditions with dioxygen as the sole oxidant. It was found that adding LA such as Sc³⁺ to Pd(OAc)₂ sharply improved its catalytic efficiency, whereas Pd(OAc)₂ alone was very sluggish. The activity improvement was attributed to the linkage of the Sc³⁺ cation to the Pd(II) species through a diacetate bridge that significantly enhanced the electrophilic properties of Pd(II) for dual C-H activation.

Photoinduced Construction of a Benzothienopyridine-S,S-dioxide Framework Enabled by Polychloropyridyl Multifunctional Motifs

Reported herein is a visible-light-induced, catalyst-free intramolecular cyclization of 4-phenylsulfonyl-2,3,5,6-tetrachloropyridine, leading to rapid assembly of a series of unprecedented benzo[4,5]thieno[3,2-c]pyridine 5,5-dioxide scaffolds under mild conditions. The rational introduction of a perchloropyridin-4-yl module significantly facilitated this photoinduced process and offers a versatile platform for broad structural variation. Mechanistic studies revealed that a newly identified charge-transfer complex with carbonate is crucial to this photoinduced process.

Construction of 3-Sulfonyl Naphthalenes via Tandem Reaction of 1,4-Diyn-3-yl Esters with Sodium Sulfinates

Polysubstituted 3-sulfonyl naphthalenes were constructed in good to high yields by AlCl₃-mediated tandem reaction of 1,4-diyn-3-yl esters and sodium sulfinates. This reaction proceeded under mild reaction conditions and tolerated a variety of functional groups. Moreover, the mechanistic studies indicated that the initial formation of allene under DBU from 1,4-diyn-3-yl ester and a sequence of nucleophilic addition of sodium sulfinate, the formation of allene, and intramolecular cyclization might be involved.

CuSO4-Catalyzed dual annulation to synthesize O, S or N-containing tetracyclic heteroacenes

In this work, CuSO4 is utilized as a practical redox catalyst for tandem dual annulation in the synthesis of indole-fused tetracyclic heteroacenes, which are important skeletons in both medicinal chemistry and materials chemistry. The preparation of such skeletons in a convenient and efficient manner is in high demand. This method realizes the modular synthesis of benzofuro-, benzothieno-, and indoloindoles from abundant feedstocks such as 2-halobenzyl halides and nitrile derivatives in up to 99% yields, providing a rapid access to diverse indole-fused heteroacenes with biological or optoelectronic properties.