The reaction of N,N-disubstitutedthioamide–bromineadducts with unsubstituted thioamide, followed by treatment with triethylamine, affords novel N′-thiobenzoylamidines along with smaller amounts of secondary products. A mechanism is proposed for the formation of the amidines. The results give an insight into the initial steps of the mechanism by which thioamides are converted into 1,2,4-thiadiazoles
ABSTRACT A mixed bases mediated protocol is developed to synthesize thioamides from N-aryl or N-alkylamide, aldehyde and elemental sulfur in water. This reaction requires no addition of external oxidant and avoids large excess of amides. Various functional groups and pharmaceutically interesting heteroaromatic rings could be introduced via this efficient procedure. GRAPHICAL ABSTRACT
A metal-free CC bond cleavage reaction of β-nitrostyrenes in the presence of elemental sulfur and secondary amines/amides is described. Elemental sulfur serves as both a raw material and an oxidant for CC bond cleavage, and secondary amines or amides are both feasible nitrogen sources. Besides mild reaction condition and simple work-up procedure, the method provided thioamides with good to excellent
描述了在元素硫和仲胺/酰胺存在下 β-硝基苯乙烯的无金属 C C 键裂解反应。元素硫既是C C 键断裂的原料又是氧化剂,仲胺或酰胺都是可行的氮源。除了温和的反应条件和简单的后处理程序外,该方法还提供了具有良好收率的硫代酰胺。
Transition-Metal-Free Cleavage of C–C Triple Bonds in Aromatic Alkynes with S<sub>8</sub> and Amides Leading to Aryl Thioamides
作者:Kai Xu、Ziyi Li、Fangyuan Cheng、Zhenzhen Zuo、Tao Wang、Mincan Wang、Lantao Liu
DOI:10.1021/acs.orglett.8b00573
日期:2018.4.20
transition-metal-free cleavage reaction of C–C triplebonds in aromatic alkynes with S8 and amides furnishes aryl thioamides in moderate to excellent yields. The remarkable features of this thioamidation include the metal-free cleavage of C–C triple bond, mild reaction conditions, as well as wide substrate scope that is particularly compatible with some internal aromatic alkynes and acetamides.