A Four‐Component Domino Reaction: An Eco‐Compatible Access to Diversified Imidazo[2,1‐b][1,3]thiazin‐5‐ones

Abstract

Am ulticomponent domino reaction of thiourea, alkyl propiolates, aldehydes, and isocyanides has been established, providing direct access to 2-aryl-5 H-imidazo[2,1-b] [1,3]thiazin-5-one scaffolds. The simplicity of execution, read-ily availables ubstrates, cheap reagents, high yields, excellent functional group tolerance, scalability,a nd good scores of environmental parameters make this synthetic strategy more efficient and worthy of furtherattention.

Regioselective Synthesis of Functionalized 1,3‐Thiazine‐4‐ones via Multicomponent Click Reaction Approach

“…designed copper‐mediated annulation of N ‐arylbenzamide substrates with 2‐mercaptoimidazole to produce polycyclic fused imidazo[2,1‐ b ][1,3] thiazinones in the presence of DMSO under inert atmosphere . Recently, our group prepared substituted thiazinone utilizing thiourea, alkylpropiolates, aldehydes and isocyanides in a two‐step approach using ethanol as a solvent . Overall, factors like, pre‐functionalized starting materials, expensive reagents, poor atom economy, tedious work up, complex purification protocols, non‐benign solvents, requirement of inert atmosphere and non‐ambient temperature turn this protocol a prominent alternative for previously reported methods.…”

A Rapid One‐Pot Five Component Sequential Access to Novel Imidazo[2,1‐b]thiazinyl‐α‐aminophosphonates

“…Recently, we have reported an efficient catalyst‐free, domino four‐component strategy for the efficient construction of highly functionalized imidazo[2,1‐ b ][1,3]thiazin‐5‐ones under microwave conditions . Interestingly, we realized that the use of dialdehydes such as terephthalaldehyde and isophthalaldehyde resulted in the products with retained aldehydic component.…”

Assembly of New Heterocycles through an Effective Use of Bisaldehydes by Using a Sequential GBB/Ugi Reaction

“…This idea prompted us to plan a sequential reaction on this aldehyde, thereby performing two successive IMCRs in a consecutive manner. As part of our continued interest in IMCRs, and to unearth a new series of bisheterocyclic imidazo[2,1‐ b ][1,3]thiazinyl/benzothiazoyl‐dipeptides, herein, we report a sequential GBB reaction between 2‐amino‐4 H ‐1,3‐thiazin‐4‐ones/benzo[ d ]thiazol‐2‐amines, bisaldehydes, and isocyanides, followed by a Ugi reaction between the as‐generated imidazo[2,1‐ b ][1,3]thiazinylbenzaldehyde/imidazo[2,1‐ b ][1,3]benzothiazolyl benzaldehyde intermediates, amines, aromatic acids, and isocyanides under microwave‐assisted, catalyst‐free conditions. To the best of our knowledge, this is the first reported synthesis of new bisheterocyclic imidazo[2,1‐ b ][1,3]thiazinyl/benzothiazoyl‐dipeptide scaffolds (Scheme ).…”

“…Looking at this observation, we considered that the effective use of an intermediate aldehyde that was generated during the initial GBB reactiono nt he 1,4phthalaldehyde could act as as uitable starting material for an Ugi reaction. This idea prompted us to plan as equential reaction on this aldehyde, thereby performing two successive IMCRsi naconsecutivem anner.A sp art of our continued interest in IMCRs, [14] andt ou nearthanew series of bisheterocyclic imidazo[2,1-b] [1,3]…”