| Thioether compounds have received extensive attention due to their important applications in pharmaceutical,biological and food chemistry.At present,there are two main ways to convert thioether compounds:the first is to construct new C-C and C-heteroatom bonds through C-S bond cleavage,and the second is to realize derivatization of thioether compounds via C-H bond functionalization of thioether compounds.Among them,the C-H functionalization reaction of thioether compounds can be further divided into the sulfur atomα-position C-H functionalized reaction and the C-H functional reaction of the sulfur atom remote.Although transition metal-catalyzed C-H functionalization and C-S bond cleavage reactions of thioether compounds have been reported,there are still many scientific problems in the transformation of such compounds:(1)The strong coordination of the lone pair of electrons of the sulfur atom is easy Poisoning transition metal catalysts;(2)The high activity of sulfur atoms leads to poor controllability and compatibility of the system.At the same time,the residual transition metal reagents limit its application in organic and biomedical synthesis to a certain extent.Therefore,it is particularly important to explore methods for promoting the selective conversion of thioether compounds without metal.Selectfluor is not only an important fluorination reagent,but also can participate in organic reactions as transition metal oxidant,Lewis acid catalyst,F~+ion initiator,free radical initiator,deprotection reagent,etc.In this article,Selectfluor as"fluorine-free"functionalization reagent realizesα-C(sp~3)-H bond functionalization,C-S bond cleavage and amide dehydration reaction of thioether compound 2-(alkylthio)benzamide by using different additives without metal.The main content of this paper includes the following four parts:The first part:Summarizes the research progress in organic reactions involving Selectfluor as a"fluorine-free"functionalizing reagent,C-H bond functionalization reaction and C-S bond cleavage reaction of thioether compounds.The second part:With the participation of Selectfluor,theα-C(sp~3)-H bond functionalization of 2-(alkylthio)benzamides was realized by using acid as additive to construct 2-Substituted-2,3-dihydrobenzothiazin-4-ones compounds;C-S bond cleavage of 2-(alkylthio)benzamides was achieved by using iodide as additives,and 2,3-dihydrobenzothiazin-4-ones were constructed.This new method achieves the intramolecular cyclization of 2-(alkylthio)benzamides through the selective transformation of thioether compounds without the participation of metals,resulting in the synthesis of two different sulfur-containing heterocyclic compounds.The third part:With sulfanyl groups as directing groups,intramolecular dehydration of 2-(alkylthio)benzamides amide groups via the generation of transient cyclic sulfur intermediates using sodium iodide and hydriodic acid to construct 2-(alkylthio)benzonitrile compounds in the presence of Selectfluor,which efficiently converts aromatic amides without metal participation is a nitrile,and higher yields are obtained.The fourth part:With amides as directing groups,direct acyloxylation of2-(alkylthio)benzamides were established using simple carboxylic acids and their corresponding salts as acyloxy sources in the presence of Selectfluor.The method is novel and simple,with a wide substrate range,high yield and good functional group compatibility. |
