Metal‐Free Selective C−S Bond Cleavage of Thioethers to Access β‐Alkoxy Carbonyl Compounds

Abstract

A metal-free C(sp 3 )À S bond cleavage of β-alkylthio carbonyl compounds in the presence of Selectfluor is described. This novel strategy realizes the CÀ S bond cleavage and subsequent CÀ O bond formation, providing a facile and efficient method to construct different important β-alkoxy carbonyl compounds with moderate to good yields and good functional groups tolerance. Moreover, our mechanistic studies also prove that two different mechanisms including the oxidant and thionium ion intermediate pathway may exist in this process.

Metal‐Free and NBS‐Mediated C(sp3)−S Bond Cleavage of Thioethers to Access Alkyl Bromides

“…The proposed mechanisms, as depicted in Scheme 6, are supported by previous reports and control experiments. [6][7][8][9][10][11] The initial reaction between 1 a and NBS produces the transient salt A, which can subsequently be converted into the crucial sulfoxide B, HBr, and succimide. The control experiment showed that sulfoxide B was formed, indicating that the NH group of 1 a could not form a four-membered ring after generating intermediate A through neighboring group participation.…”

“…The sulfoxide B can be transformed into acrylamide C at an elevated temperature. [8,9] Subsequently, the desired product 2 a is generated from either sulfoxide B or acrylamide C in the presence of in-situ formed HBr (path a). On the other hand, when using substrate 1 p, the initial transient salt D quickly converts into transient salts E, which can be further transformed into the final product 2 p along with byproduct 3 (path b).…”

“…[7] Furthermore, we have also reported the metal-free selective cleavage of C(sp 3 )À S bonds in 3-(methylthio)-N-arylpropanamides to access N-substituted acrylamides, β-aminopropanamides and β-alkoxy carbonyl compounds in the presence of Selectfluor (Scheme 1c). [8,9] Based on our ongoing efforts in sulfur chemistry, [10,11] herein we disclose the NBS-mediated selective C(sp 3 )À S bond cleavage of thioethers to access organic alkyl bromides (Scheme 1 d). Notably, this is the first example where NBS has been employed for both CÀ S bond cleavage and subsequent bromination reaction.…”

Transition-metal-free C–S bond cleavage and transformation of organosulfur compounds

“…8 Moreover, halogenated reagents are also valuable in organic synthesis, and the following reagents are commonly used, including KF, Selectfluor, NFSI, NBS, NCS, NIS, I 2 , PhI(OAc) 2 , etc. 9–14 Wei's review 6 d outlined a transition-metal-free rearrangement reaction of thioethers with ortho -silylaryl triflates in the presence of KF or CsF. 9 The in situ formed arynes from ortho -silylaryl triflates react with thioethers to yield sulfonium intermediates, which is followed by subsequent C–S bond cleavage and transformations.…”

dl‐Methionine‐Mediated Reversible Deactivation Radical Polymerization of Styrene and Methyl Methacrylate

“…[ 62 ] Ke Yang's group reported that in CS bond cleavage of thioethers (e.g., 3‐(methylthio)‐N‐phenylpropanamide), the CS bond with the lower bond energy was broken and the yield was 87%. [ 63 ] Furthermore, weak CS bond is easily cleaved in polar solvents through a nucleophilic attack on the positively disposed carbon center, which is followed by cleavage of the CS bond. [ 64 ] To our knowledge, dl ‐Methionine could be directly selected as control agent for RDRP has not been investigated.…”