Silver-Promoted Site-Selective Intramolecular Cyclization of 2-Methylthiobenzamide Through α-C(sp³)–H Functionalization

Abstract

Silver-mediated intramolecular α-C­(sp3)–H bond functionalization of the methylthio group has been established in the presence of Selectfluor as an additive. This novel strategy provides efficient access to various diverse sulfur-based heterocycles with good yields and functional group compatibility. It is noteworthy that the completely novel benzooxathiin-4-imine skeletons were reported for the first time in this study.

Metal-free and Selectfluor-mediated diverse transformations of 2-alkylthiobenzamides to access 2,3-dihydrobenzothiazin-4-ones, benzoisothiazol-3-ones and 2-alkylthiobenzonitriles

“…Based on the control experiments and previous literature, 9,10,16–19 the proposed reaction pathways are shown in Scheme 8. The initial transient fluorosulfonium salt A is formed in the presence of Selectfluor and substrate 1a , and can be converted to the cyclic sulfonium intermediate D .…”

“…7 Furthermore, it has also been utilized as the single electron transfer source to generate a highly reactive species TEDA 2+ ˙ ( N -(chloromethyl)triethylenediamine). 8 Although substantial efforts have been devoted in organic chemistry, the use of Selectfluor as an alkyl source has never been reported, and only a few examples focused on Selectfluor-mediated selective C–S bond cleavage 9 or C–H functionalization 10 of thioether skeletons. In our continuing efforts in sulfur chemistry, 11 herein we disclosed the Selectfluor-mediated diverse transformations of 2-alkylthiobenzamides to access different kinds of 2,3-dihydrobenzothiazin-4-ones and benzoisothiazol-3-ones.…”

Recent Advances in the Application of Selectfluor as a “Fluorine‐free” Functional Reagent in Organic Synthesis

“…[4] Besides, other transition metal catalysts, such as, Ag, Cu, Fe and Pd could also be well oxidized by Selectfluor and applied in different organic synthesis. [10][11][12][13][14][15][16][17][18][19][20][21] In 2015, Qing and coworkers reported a novel method for the construction of alkyl trifluoromethyl ethers through Ag-promoted oxidative trifluoromethylation of alcohols with TMSCF3 in the presence of Selectfluor (Scheme 1a). [9] Following this study, the same group updated the reaction system to broaden the substrate scope.…”

“…Very recently, our group aslo demonstated the Ag2O-mediated C−H bond functionalization of 2-methylthiobenzamide in the presence of Selectfluor as the transition metal oxidant (Scheme 3). [15] This process provided efficient access to various important sulfur-containing heterocyclic derivatives including benzooxathiin-4-imines and benzothiazin-4-ones with good functional group compatibility.…”

Selectfluor as “Fluorine-Free” Functional Reagent Applied to Organic Synthesis under Transition Metal-Free Conditions

“…这些方法相较于 Selectfluor 与过渡金属协同催化的 反应而言 [102][103] , 避免了使用昂贵的过渡金属, 反应体 系简单, 且反应条件更加温和, 表现广泛的底物适用性 及高效的区域选择性, 尤其是在复杂的环化反应中, 体 现出优异的官能团耐受性. 相对可见光诱导的有机反应 而言 [104][105] , Selectfluor 作为自由基引发剂, 替代了催化 效果不佳的光敏剂及传统的过渡金属光催化剂, 具有绿 色环保、经济高效等优点.…”