Photocatalytic Bicyclization of Indole-Tethered 1,6-Enynes for Diastereoselective Synthesis of Pyrrolo[3,2,1-jk]carbazoles.

A visible-light-driven photocatalytic protocol is established for the diastereoselective synthesis of pyrrolo[3,2,1-jk]carbazoles via a radical-triggered multicomponent bicyclization reaction starting from readily available indole-tethered 1,6-enynes and α-benzyl-α-bromomalonates under mild conditions. This photocatalytic approach exhibits a wide substrate compatibility and excellent tolerability toward various functional groups and boasts the benefit of efficient ring formation and chemical bond creation.

Photocatalytic Thio/Selenosulfonylation-Bicyclization of Indole-Tethered 1,6-Enynes Leading to Substituted Benzo[c]pyrrolo[1,2,3-lm]carbazoles.

The photocatalyzed radical-triggered thio/selenosulfonylation-bicyclization of indole-tethered 1,6-enynes has been established for the first time, enabling the synthesis of various previously unreported thio/selenosulfonylated benzo[c]pyrrolo[1,2,3-lm]carbazoles with moderate to good yields under mild conditions. The reaction pathway was proposed, consisting of energy transfer, homolytic cleavage, radical addition, 5-exo-dig, radical coupling, and a Mallory reaction cascade. This approach exhibits a wide substrate compatibility and excellent tolerability toward various functional groups and is characterized by its remarkable efficiency in both bond formation and annulation.

Electrochemical selective annulative amino-ketalization and amino-oxygenation of 1,6-enynes.

A new electrochemical selective annulative amino-ketalization and amino-oxygenation of 1,6-enynes with disulfonimides and alcohols is reported, producing a series of functionalized benzofurans under catalyst- and oxidant-free conditions. The annulative aminoketalization proceeds with simple short-chain alcohols such as methanol, ethanol and n-propanol as O-nucleophilic reagents, while the reaction occurs in the annulative aminooxygenation direction in the presence of water and large steric sec-butyl alcohol (SBA).

Metal-Catalyzed Spiroannulation-Fluoromethylfunctionaliztions of 1,5-Enynes for the Synthesis of Stereodefined (Z)-Spiroindenes.

Two classes of new catalytic spiroannulation-fluormethylfunctionaliztions of para-quinone methide (p-QM)-containing 1,5-enynes have been established under redox-neutral conditions. Palladium-catalyzed spiroannulation-iododifluoromethylation with ethyl difluoroiodoacetate oriented completely stereoselective access to (Z)-spiroindenes and the latter included copper-catalyzed three-component spiroannulation-cyanotrifluoromethylation starting from Togni's reagent and trimethylsilanecarbonitrile (TMSCN). Both reaction pathways involve fluoroalkyl radical-triggered 1,6-addition/5-exo-dig annulation/metal radical cross-coupling/reductive elimination sequence, providing practical and stereoselective protocols for rapidly constructing cyclohexadienone-containing spiroindenes with generally good yields.

Electrochemical Annulation-Iodosulfonylation of 1,5-Enyne-containing para-Quinone Methides (p-QMs) to Access (E)-Spiroindenes.

A new electrochemical three-component annulation-iodosulfonylation of 1,5-enyne-containing para-quinone methides (p-QMs) has been established by using available arylsulfonyl hydrazides and potassium iodide under environmentally benign conditions. The electrosynthesis offers sustainable and efficient access to construct spirocyclohexadienone-containing (E)-indenes without any additional catalyst or oxidant through a sulfonyl-radical-triggered 1,6-addition and an I+-mediated ipso-cyclization cascade. Notably, potassium iodide plays the triple role of an electrolyte, a redox catalyst, as well as an iodination reagent.