Phosphine‐Promoted Amide Bond Formation Reactions from Carboxylic Acids and Tetraalkylthiuram Disulfides

Abstract

An efficient protocol for the straightforward synthesis of amides from readily available carboxylic acids and tetraalkylthiuram disulfides is presented. The reaction proceeds through direct cross‐coupling reactions promoted by catalytic amount of PPh3 in DMSO. This protocol is compatible with a wide variety of electron‐donating and ‐withdrawing acids, which shows its practical synthetic value in organic synthesis.

Generation of Coumarin‐3‐Carboxamides From Coumarin‐3‐Carboxylic Acids and Tetraalkylthiuram Disulfides Catalyzed by Copper Salts

“…Based on the previous reports [15a–b,f–g,16,17] and our obtained results, a plausible reaction pathway was tentatively proposed and described in Scheme 4. Firstly, the thiuram reagent 2 a produces nucleophilic intermediate I , [18] which reacts with coumarin‐3‐carboxylic acid 1 a , to afford the intermediate II .…”

Amidation Reaction of Quinoline‐3‐carboxylic Acids with Tetraalkylthiuram Disulfides under Simple Conditions: A facile Synthesis of Quinoline‐3‐carboxamides

“…In light of the mentioned experiments and preceding literature, [12,13,15b,e,16] a plausible mechanistic network was proposed in Scheme 4. Tetramethylthiuram disulfide 2 a is nucleophilic attacked by quinoline‐3‐carboxylic acid 1 a to give rise to intermediate I , along with the release of side‐product II .…”

“…Recently, Dong and co-workers [12] realized a copper catalyzed protocol for the formation of benzamides using tetraalkylthiuram disulfides (TATD) as amine sources. Our group [13] has reported the amidation of benzoic acids promoted by phosphine, while the quinolinyl and pyridinyl carboxylic acids did not undergo the reported transformation. Probably because of the electrondeficient nature of pyridine ring, which alters the electronic properties of the conjugate system, thus leading to insufficient efficiency of the above method.…”

“…Compounds were visualized by irradiation with UV light (254 nm). 1 H NMR and 13 C NMR spectra data were recorded by a BRUKER AVANCE III 400 MHz spectrometer ( 1 H 400 MHz, 13 C 100 MHz), using CDCl 3 as the solvent with tetramethylsilane (TMS) as the internal standard at room temperature. Chemical shifts are reported as δ-values in ppm relative to the deuterated solvent residual peak (δ = 7.26 ppm for 1 H NMR and 77.0 ppm for 13 C NMR).…”

“…Therefore, developing an efficient amidation of quinoline carboxylic acids using tetraalkylthiuram disulfides as the amine source would be interesting from viewpoint of synthetic chemistry. Based on the above understanding and our previous works, [13,15] we wish to present herein an efficient synthesis of quinoline carboxamides from quinoline carboxylic acids with tetraalkylthiuram disulfides under simply operations (Scheme 1, e).…”