An electrochemical-enabled cascaded cyclization of enaminones with potassium thiocyanate and alcohols to access 2-alkoxythiazoles

Abstract

An electrochemical enabled three-component cascaded cyclization of enaminones with potassium thiocyanate and alcohols to access 2-alkoxythiazoles has been developed under external oxidant-free conditions. The reaction proceeded smoothly through the electrochemical...

HFIP-Mediated Multicomponent Reactions: Synthesis of Pyrazole-Linked Thiazole Derivatives

“…Very recently, Li et al reported synthesis of disubstituted thiazole derivatives from a three-component reaction of enaminones with potassium thiocyanate and alcohols using electro-organic synthesis (Scheme 1, eq f). 32 In this method also, excess amount of LiClO 4 is required. Although all these methods are very useful for the synthesis of substituted thiazoles, they suffer from one or another limitation such as the use of harsh reaction conditions, the use of a base or strong acid or additive, long reaction time, as well as use of excess amount of reagents, which are considered as detrimental in terms of green chemistry.…”

“…In this electro-organic synthesis, strong acid HCl is required. Very recently, Li et al reported synthesis of disubstituted thiazole derivatives from a three-component reaction of enaminones with potassium thiocyanate and alcohols using electro-organic synthesis (Scheme , eq f) . In this method also, excess amount of LiClO 4 is required.…”

NBS-Promoted Synthesis of Thiocyanated Aminomaleimides and Site-Selective Intramolecular Cyclization Access to 1,4-Benzothiazepines via S–CN Bond Cleavage

“…As a result, the development of efficient protocols that allow the introduction of -SCN onto different substrates and the subsequent thiocyano transformation cascades enabling the construction of diverse organic compounds would be highly desirable. On the other hand, enaminones, as valuable and easily available synthons, have been recently investigated extensively in thiocyanation reactions for the synthesis of structurally diverse thiocyanates or derived heterocycles . Various progress such as NBS, oxidants, visible light, electricity, and ultrasound have been employed to promote thiocyanation of different enaminones, leading to thiocyanated enaminones and S/N-heterocycles.…”

“…On the other hand, enaminones, as valuable and easily available synthons, have been recently investigated extensively in thiocyanation reactions for the synthesis of structurally diverse thiocyanates or derived heterocycles . Various progress such as NBS, oxidants, visible light, electricity, and ultrasound have been employed to promote thiocyanation of different enaminones, leading to thiocyanated enaminones and S/N-heterocycles. However, most of the above methods remained in the thiocyanation stage or further annulation of thiocyanated enaminones based on the nucleophilic site (N1) with S–CN for accessing various thiazole products (Scheme b) .…”

Self‐ or Acridinium‐Catalyzed Electrophotosynthesis of Thiocyanato Heterocycles from Activated Alkenes

“…They are also versatile synthons which could be converted with ease to other sulfur-containing molecules such as thiols, thioethers, carbamothioates, thiotetrazole, perfluoromethylsulfanes and phosphinothioates. [23] Over the past decades, a wide range of methodologies have been developed to construct organic thiocyanates using an N-SCN agent, [24] TMSSCN [25] or KSCN, [26][27][28][29][30][31][32][33][34] or through sulfur cyanation. [35] The inexpensive and benchtop-stable KSCN is a particularly versatile thiocyanating agent, which might undergo a nucleophilic, [26][27][28][29] electrophilic [30,31] or radical coupling [32][33][34] under the conditions of an oxidant, [26,30,32] visible-light irradiation [27,33] or electrolysis.…”