Synthesis of 2‐Substituted Benzothio(seleno)phenes and Indoles via Ag‐Catalyzed Cyclization/Demethylation of 2‐Alkynylthio(seleno)anisoles and 2‐Alkynyldimethylanilines

Abstract

An Ag-catalyzed cyclization/demethylation of 2-alkynylthio (seleno)anisoles and 2-alkynyldimethylanilines is described and applied for the construction of valuable benzothio(seleno) phenes as well as indoles. Various 2-substituted benzothio (seleno)phenes and indoles were obtained in good to excellent yields under mild reaction conditions with low catalyst loading. An application of this new method is also exemplified with a concise synthesis of a bioactive molecule precursor. Furthermore, a conceivable reaction mechanism is proposed with supports from isotope-exchange experiments.

Synthesis of benzothiophenes via sulfonium-[3,3]-rearrangement of aryl sulfoxides with allenenitriles

“…In order to improve the efficiency of the final heterocyclization, a series of Brønsted acids and Lewis acids were screened as additives for treating the residual rearrangement product 3 (entries 7–11). 17 The use of HOAc slightly improved the yield of the final product 4aa (entry 7), while other Brønsted and Lewis acids resulted in lower yields of 4aa (entries 8–10). Silica gel was identified as the best additive which afforded the desired product 4aa in a good yield (71%, entry 11).…”

“…Based on experimental observations and related literature, 16 e ,17 a possible reaction mechanism was outlined as shown in Scheme 6. The reaction consists of four steps: (1) Tf 2 O initiates the electrophilic assembly of aryl sulfoxide and allenenitrile.…”

Palladium-catalyzed synthesis of 2,3-disubstituted indoles via arylation of ortho-alkynylanilines with arylsiloxanes

“…9 However, it remains a challenge to synthesize 2,3-disubstituted indoles in a regio-selective manner. To solve this problem, Larock and co-workers 10 and many research groups 11–14 have developed various methods for the preparation of substituted indoles.…”