Four-Component Approach to N-Substituted Phenothiazines under Transition-Metal-Free Conditions

Abstract

An efficient synthesis of N-substituted phenothiazines has been developed from readily available amines, cyclohexanones, and elemental sulfur. The combination use of KI/DMSO in an oxygen atmosphere significantly improved the reaction yields.

Recent Advances in Iodine‐Promoted C−S/N−S Bonds Formation

“…Additionally, Deng and co‐workers elegantly accomplished a KI/DMSO‐promoted four‐component example for the synthesis of N‐substituted phenothiazines 172 from readily available cyclohexanones 170 , amines 171 and elemental sulfur (Scheme 54). [131] In this reaction, the condensation, dehydrogenation, tautomerization, and double C−S bonds formation were achieved in one pot with the aid of a KI/DMSO/O 2 system. Based on the observations and the literatures, the authors proposed a possible mechanism that a radical cyclization process might be involved for the construction of intermediate 173 , which endured consecutive oxidation to afford the final product 172 .…”

One‐Pot Synthesis of 2,3,5‐Trisubstituted Thiophenes through Three‐Component Assembly of Arylacetaldehydes, Elemental Sulfur, and 1,3‐Dicarbonyls

“…In this context, multicomponent synthesis and cascade reactions show great potential to provide opportunities for rapid preparation of target compounds through predesigned routes . To develop facile synthesis of functionalized heterocycles, we have contributed a number of examples of multicomponent reactions including sulfur‐involved synthesis of phenothiazines, benzothiophenes, thiadiazoles,, and benzothiazoles. Herein, we disclose the novel self‐assembly of arylacetaldehydes, elemental sulfur, and 1,3‐dicarbonyls to access 2,3,5‐trisubstituted thiophenes under base conditions.…”

“…Also, few examples of multicomponent reactions led to the construction of thiophene rings from readily available chemicals ,. In the past years, we and others programmed on the facile synthesis of sulfur‐containing heterocycles by using nontoxic and bench‐stable elemental sulfur –,. However, to our knowledge there are few examples to use it for direct thiophene formation to date .…”

Chromatography‐Free Multicomponent Synthesis of Thioureas Enabled by Aqueous Solution of Elemental Sulfur

“…These transformations are responsible for the activation of elemental sulfur, which can then be used as efficient sulfurating reagent [17] . Recently a couple of innovative, multicomponent and one‐pot procedures have been published for the use of elemental sulfur in synthetic procedures [20–26] . Numerous methods rely on the known transformation of isocyanides to isothiocyanates with elemental sulfur in the presence of base or various metal catalysts, [19,27–35] which is utilized in particular for the synthesis of thioureas (Scheme 1).…”