Metal‐Free Synthesis of Benzothiophenes by Twofold C−H Functionalization: Direct Access to Materials‐Oriented Heteroaromatics

Abstract

Due to their ubiquity in nature and frequent use in organic electronic materials,b enzothiophenes are highly sought after.H ere we set out an unprecedented procedure for the formation of benzothiophenes by the twofold vicinal CÀH functionalization of arenes that does not require metal catalysis.T his one-pot annulation proceeds through an interrupted Pummerer reaction/[3,3]-sigmatropic rearrangement/ cyclization sequence to deliver various benzothiophene products.T he procedure is particularly effective for the rapid synthesis of benzothiophenes from non-prefunctionalized polyaromatic hydrocarbons (PAHs).

Heteroatom-Embedding Annulative π-Extension (Hetero-APEX) Reactions: An Overview

“…In 2019, Procter and co-workers achieved a thia-APEX reaction to construct methylthiophene rings onto various unfunctionalized aromatics such as benzenes, naphthalenes, and PAHs (Scheme 25 ). 36 In this reaction, chloro(methylsulfinyl)propane 91 is considered to be activated by Tf 2 O to form sulfonium triflate A , which can directly react with unfunctionalized aromatics 90 to afford allylarylmethylsulfonium intermediates B . Then, this intermediate B can undergo [3,3]-sigmatropic rearrangement and rearomatization to give intermediates C and D , followed by proton-assisted intramolecular nucleophilic addition by the sulfur atom to form cyclic methylsulfonium intermediates E .…”

Straightforward Access to Thiocyanates via Dealkylative Cyanation of Sulfoxides

“…After the electrophilic activation of the sulfoxide to intermediate I 1 , the addition of TMSCN forms cyanosulfonium triflate I 2 . 14 This species is readily dealkylated by the counteranion to reveal thiocyanate and the alkyl triflate. 6 , 7 To provide further evidence of this mechanism, we subjected cyclic sulfoxide 1p to the reaction conditions ( Scheme 3 b).…”