Organic Transformation of Benzothiophenes by C−S Bond Cleavage Beyond Reductive Desulfurization

Abstract

As the analogues of indole bicyclic system, benzothiophenes are often overlooked in organic transformation, and synthetic methods developed mostly rely on the acidic protons at C2 or C3 position, known as CÀ H functionalization. Complementary to the structural modification of benzothiophenes, CÀ S bond cleavage can realize the skeleton reconstruction. Reduction of benzothiophenes always involves the CÀ S bond cleavage, especially in the hydrodesulfurization (HDS) of petroleum products. Beyond reductive desulfurization, although CÀ S bond cleavage of benzothiophenes has been achieved by diverse methodologies, there is no systematic review on such topic. Herein, transformation of benzothiophenes via CÀ S bond cleavage in organic synthesis will be presented along with briefly delineated mechanism.

Revisiting Peri‐Aryloxyquinones: From a Forgotten Photochromic System to a Promising Tool for Emerging Applications

“…However, most researchers have been using and further optimizing compounds of these few established compound families, thereby ignoring the fact that there are other, less prominent classes of photoswitches that indeed may offer unique advantages. Among them are for example indigos [141] and indigoids [26b] but also the PAQs reviewed herein can serve as interesting alternatives. From the previous sections it becomes clear that there are some key features of this interesting and often neglected family of photochromic compounds including:…”

Unusual Regio‐ and Chemoselectivity in Oxidation of Pyrroles and Indoles Enabled by a Thianthrenium Salt Intermediate

“…As shown in Figure 2, this motif is found in antimalarial azaaurones, [27] as well as in natural products such as aristotelone, [28] (±)‐erucalexin [29] and duocarmycin B2 [30] . Indolin‐3‐ones unsubstituted at the 2‐position can undergo air oxidation [31] (via their indoxyl tautomers) to indigos [32,33] (Scheme 2A), with the rate depending on the substituents (this cannot occur for 2‐substituted indolin‐3‐ones).…”