Regioselective Thiolation of Arenes and Heteroarenes: C–H Functionalization Strategy for C–S Bond Formation

Abstract

A facile transition-metal-free oxidative cross-dehydrogenative coupling reaction involving selective formation of a C-S bond leading to the synthesis of arylthiobenzoxazoles, heteroarylthiobenzoxazoles, and arylthiobenzothiazoles has been described. This highly regioselective C-H functionalization reaction with electron-rich aromatic systems including heteroaromatics is achieved by reversing the reactivity of sulfur in the presence of a suitable oxidant and strong acid.

Three‐Component Synthesis of 2‐Substituted Thiobenzoazoles Using Tetramethyl Thiuram Monosulfide (TMTM) as Thiocarbonyl Surrogate

“…[6] Several representative examples are shown in Figure 1, such as compound a (an anticonvulsant agent), [7] compound b (a telomerase inhibitor), [8] compound c (an antinematode), [9] and compound d (an antimycobacte- So far, several ways have been reported to synthesize 2benzyl/allyl-substituted thiobenzoazoles (Scheme 1). [13][14][15] Among these strategies, transition metal catalysis and toxic reagents are frequently used, and the obtained intermediates often need to be separated and purified, which lead to tedious process. Furthermore, direct use of raw materials, such as 2mercaptobenzothiazoles which are not always commercially available, would also limit the application of these methods.…”

Sustainable and Site‐Selective C−H Sulfenylation of Aromatic Compounds with Thiol using Catalytic Graphene Oxide and NaI

“…Transition‐metal‐catalyzed regioselective sulfenylation of indoles has been reported with various metals like Cu, Fe, Mg, Ce, V, Ru, etc., using both thiol and other sulfur‐based reagents like sulfonyl chloride, N ‐(arylthio)phthalimide and disulfide . Direct C−H sulfenylations of aromatic compounds have been reported either using peroxides or transition‐metal catalysts in combination with DMSO,– and C−H thiocyanation using GO‐H 2 O 2 . Considering the toxicity as well as a high cost of various transition‐metal‐based catalysts, metal‐free approaches have also been developed.…”

Recent Advances in the C(sp2)-S Bond Formation Reactions by Transition Metal-Free C(sp2)-H Functionalization

“…随后, Cossy 小组 [7] 同样以 N-硫代丁二酰亚 图式 2 N-硫代丁二酰亚胺为硫源的富电子苯 C-H 硫芳基化 反应 Scheme 2 N-Thiobutanimides as thio sources for the sulfenylation of electron rich benzenes 图式 3 硫酚/硫醇为硫源的富电子苯 C-H 硫芳基化反应 Scheme 3 Thiophenols/thiols as thio sources for the sulfenylation of electron rich benzenes Baumgartner 等 [11] 曾在研究硝基烷烃类化合物的硫 芳基化反应中发现二芳基二硫醚作为硫源和萘酚发生 反应可得到相应的羟基萘硫醚, 反应需通过分别采用叔 丁醇钾和盐酸分两步处理完成. Prabhu 小组 [12] 通过苯并 噁唑-2-硫酮/苯并噻唑-2-硫酮 21 在三氟甲磺酸(TfOH) 催化下异构化为相应的硫醇, 以过硫酸钾为氧化剂, 硫 醇作为硫源和苯酚/苯甲醚类化合物 22 反应, 在 60 ℃ 加热可发生脱氢偶联反应得到硫醚类产物 23. 当采用 富电子杂环类化合物如噻吩/苯并噻吩 24 作为另一反应 底物时, 在同样氧化剂和酸催化作用下, 可得到相应的 双杂环硫醚产物 25, 反应在室温即可进行(Scheme 5).…”