K2S2O8-Promoted Aryl Thioamides Synthesis from Aryl Aldehydes Using Thiourea as the Sulfur Source

Abstract

Thiourea as a sulfur atom transfer reagent was applied for the synthesis of aryl thioamides through a three-component coupling reaction with aryl aldehydes and N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAC). The reaction could tolerate various functional groups and gave moderate to good yields of desired products under the transition-metal-free condition.

Synthesis of 5-Trifluoromethyl-Substituted (Z)-N,N-Dimethyl-N′-(pyrazin-2-yl)formimidamides from 2-Aminopyrazines, LiI/Selectfluor, FSO2CF2CO2Me and DMF under Cu Catalysis

“…Based on our previous work 17,23 and the control experiments (see Scheme 4), a possible mechanism is outlined in Scheme 5. The reaction between pyrazine 1 and Selectfluor (3) via single-electron transfer (SET) in DMF at 15 24 at 100 °C then occurs to form F. The reaction of F with DMF under Cu catalysis gives G, which undergoes dehydration to produce 5 and regenerates CuI. 13,25 Interestingly, CuI functions as a catalyst for the domino trifluoromethylation and the condensation.…”

“…14 Consequently, regioselective trifluoromethylation of a heteroaryl ring under Cu catalysis remains a big challenge. N,N-Dimethylformamide (DMF) is a common solvent and is utilized as a reagent for the synthesis of aldehydes 15 and amides. 16 However, the Cu-catalyzed condensation between a CF 3 -substituted heteroaryl amine and DMF has not been described as yet.…”

Towards More Practical Methods for the Chemical Synthesis of Thioamides Using Sulfuration Agents: A Decade Update

“…In the workup procedure, the remaining thionating reagent can be transferred to solvents by addition of water and the target products can be easily obtained with high purity by recrystallization. Organosulfur is also a well-documented source of sulfur to construct thioamides, especially thiols [65], disulfides [66][67][68], and thiourea [69], primary or secondary thioamides [70,71], and 1,2,3-thiadiazoles [72]. How-ever, organosulfur compounds are featured as catalyst poisons for transition metals due to their ability to coordinate metallic species [73], which sometimes limits their application.…”

Copper‐catalyzed synthesis of α‐ketothioamides from ketones

“…[16,17] Different methods are available in the literature for the synthesis of thioamide derivatives including decarboxylative thioamidation, [18] thioamidation by redox reaction, [19] thioamidation utilizing styrene or alkyne, [20,21] and so forth. [22,23] Literature survey shows that thioamidation has been performed upon acetophenone derivatives as the starting materials (Scheme 1). Utilizing S 8 and an amine source in this reaction, α-ketothioamide is expected to be generated as the final product.…”