Ultrasound-Promoted Synthesis of α-Thiocyanoketones via Enaminone C═C Bond Cleavage and Tunable One-Pot Access to 4-Aryl-2-aminothiazoles

Abstract

Ultrasound has been successfully employed to promote the thiocyanation of the CC bond in enaminones for the synthesis of α-thiocyanoketones and 2-aminothiazoles. The reactions of enaminones with ammonium thiocyanate provide αthiocyanoketones with ultrasound irradiation at room temperature. More interestingly, simply further heating the vessel after ultrasonic irradiation leads to the selective synthesis of 2-aminothiazoles with an unconventional 4-aryl substructure.

Photocatalytic C–H Thiocyanation of NH2-Enaminones and the Tunable Synthetic Routes to 2-Aminothiazoles and 2-Thiazolinones

“…Subsequently, thiocyanation reactions on similar enaminones and enamines have been also realized by other groups with either oxidant-mediated thermoreactions or electrode oxidation reactions . In addition, our rather recent work disclosed that ultrasound can promote the selective carbon–carbon bond thiocyanation by fully splitting the double bond in enaminones . Interestingly, despite the fact that N,N-disubstituted enaminones have been successfully used as the C–H bond donors for C–H thiocyanation by photocatalysis, , equivalent C–H thiocyanation reactions of the free NH 2 -enaminones has not hitherto been realized by photocatalysis.…”

“…11 In addition, our rather recent work disclosed that ultrasound can promote the selective carbon− carbon bond thiocyanation by fully splitting the double bond in enaminones. 12 Interestingly, despite the fact that N,Ndisubstituted enaminones have been successfully used as the C−H bond donors for C−H thiocyanation by photocatalysis, 9,10a equivalent C−H thiocyanation reactions of the free NH 2 -enaminones has not hitherto been realized by photocatalysis. In this context, developing a practical photocatalytic method for the C−H thiocyanation of NH 2enaminones is currently highly desirable for making the synthesis of thiocyanoenaminones and their derivatives more sustainable.…”

Iodine‐Mediated Three‐Component Strategy to Synthesize 2‐Aminothiazoles from β‐Diketones/β‐ketoesters, Arylamines and Ammonium Thiocyanate

“…In the same year, Retailleau and Nguyen disclosed a base‐catalyzed reaction of chalcones, isothiocyanates, and elemental sulfur to produce thiazole‐2‐thiones (Scheme 1d) [10] . Recently, Wan and co‐workers (2022) developed a tunable one‐pot synthesis to synthesize 4‐aryl‐2‐aminothiazoles from enaminones and ammonium thiocyanate (Scheme 1e) [11] . Lin and co‐workers also reported a cascade method to synthesize 2‐aminothiazoles employing tertiary enaminones, potassium thiocyanate, and anilines (Scheme 1f) [12] .…”

“…[10] Recently, Wan and co-workers ( 2022) developed a tunable one-pot synthesis to synthesize 4-aryl-2-aminothiazoles from enaminones and ammonium thio- www.eurjoc.org cyanate (Scheme 1e). [11] Lin and co-workers also reported a cascade method to synthesize 2-aminothiazoles employing tertiary enaminones, potassium thiocyanate, and anilines (Scheme 1f). [12] In the same time period, Wan and his team developed an elegant electrochemical method for the construction of 2-aminothiazoles from enaminones and thioureas via α-CÀ H thiolation of enamines and CÀ N bond amination (Scheme 1g).…”

Thiazole-5-carbaldehyde Synthesis by Cascade Annulation of Enaminones and KSCN with Dess–Martin Periodinane Reagent

“…Particularly, employing enaminones as the main building blocks for the construction of aromatic ring systems has gained significant success. In the presence of proper reaction partners and/or with proper conditions, enaminones have been employed for the construction of phenyl, pyridine, pyrrole, pyrazole, quinoline, indole, pyrimidines, thiazoles, 1,2,3-triazoles azirines, and diverse other heteroaromatic ring systems . Based on these achievements, it is possible to develop an applicable method for synthesis of aromatic compounds with useful functional groups such as aromatic aldehydes.…”