Visible-Light-Induced Cyclization/Aromatization of 2-Vinyloxy Arylalkynes: Synthesis of Thio-Substituted Dibenzofuran Derivatives

Abstract

A visible-light-induced cascade reaction of 2-vinyloxy arylalkynes with thiosulfonates was developed and provided unexpected thio-substituted dibenzofuran derivatives in moderate yields. Mechanistic studies revealed the thiosulfonylation product of 2-vinyloxy arylalkyne was the key intermediate, and the additive disulfide played the role of hydrogen abstraction in the aromatization process to offer the desired product. This reaction presents a new reaction mode for the construction of polycyclic oxygen heterocycles.

Tetramethylammonium Iodide (TMAI)‐Promoted Sulfenylation/Annulation of Enaminones with Thiosulfonates

“…Thus, on the basis of the experimental results above and previous related literature, [12,15a–d] a plausible mechanism is proposed in Scheme 4. This reaction involves the following key steps: Firstly, the homolysis of sulfonothioates 2 possibly would yield an ArS .…”

Visible-Light-Induced Radical Cascade Reaction of 1-Allyl-2-ethynylbenzoimidazoles with Thiosulfonates to Assemble Thiosulfonylated Pyrrolo[1,2-a]benzimidazoles

“…In Maes’s work and our previous report, thiosulfonates were reported to undergo cleavage to generate thio and sulfonyl radicals through an energy transfer pathway promoted by photocatalysis. Thus, the possible pathway was proposed as shown in Scheme .…”

“…The cascade reactions of 1, n -enynes to assemble fused heterocycles have not been reported. We have reported a photocatalytic cascade reaction of 2-vinyloxy arylalkynes with thiosulfonates to provide thio-substituted dibenzofuran derivatives . Given the continuous interest in the study of thiosulfonates, herein, we developed a visible-light-induced domino radical reaction of 1-allyl-2-ethynylbenzoimidazole with thiosulfonates to provide the thiosulfonylated pyrrolo­[1,2- a ]­benzimidazoles.…”

Visible Light‐Mediated Manipulation of 1,n‐Enynes in Organic Synthesis

“…Thereafter, the construction of thio-substituted dibenzofuran derivatives 109 was achieved by Chen and co-workers via Na 2 -Eosin-Y catalysed cyclization of 1,6-enynes 61 with thiosulfonates 108, affording the cyclized products 109 in moderate to good yields (Scheme 33a). [79] The reaction protocol implied that the addition of 1,2-diphenyldisulfane (as an additive) significantly improved the reaction efficiency. A library of 1,6-enynes 61 and thiosulfonates 108 with electron-withdrawing and electron-rich groups at various positions of the phenyl ring reacted well, delivering the needed products in good yields.…”