Efficient construction of C–N and C–S bonds in 2-iminothiazoles via cascade reaction of enaminones with potassium thiocyanate

Abstract

A novel and highly efficient protocol has been developed for the regioselective synthesis of 2-iminothiazole derivatives with potential biochemical interest by the reaction of enaminones, potassium thiocyanate (KSCN), and N-bromo succinimide (NBS) under mild conditions. The reaction proceeds via the formation of α-bromo enaminones as a versatile intermediate followed by thiocyanation/intramolecular cyclization in a one pot manner. The developed method is particularly attractive due to various advantages including operational simplicity, mild conditions, being catalyst free, and high bond-forming efficiency. The proposed protocol explores the synthetic routes of thiazoles by using various functional enaminones.

I2 Promoted Synthesis of 2‐Aminothiadiazoles Employing KSCN as a Sulfur Source Under Metal‐Free Conditions

“…According to the results of these control experiments and previous studies, a plausible mechanism for the synthesis of 2‐aminothiadiazoles was outlined in Scheme . Firstly, the N ‐tosylhydrazones A was formed and then transformed into iodonium salt B in the presence of I 2 .…”

N-Halo Reagents: Modern Synthetic Approaches for Heterocyclic Synthesis

“…Chen, Huang, Liu, and co-workers developed a one-pot NBS-induced cascade reaction for the synthesis of 2-iminothiazoles 308 from enaminones 307 (Scheme 75). 138 The optimal conditions for this cyclization were the combination of 307, NBS (2 equiv), and KSCN (1 equiv) as a thiocyanating reagent in acetonitrile at room temperature. It is proposed that the reaction occurs via tandem double nucleophilic substitution/N-cyclization.…”

Three-Component One-Pot Synthesis of Highly Functionalized Bis-Indole Derivatives

“…Recently, our group has developed several novel MCRs based on enaminones that can offer convenient and efficient access to heterocycles and fused heterocycles. 17 For the purpose of continuing our previous endeavors in and furthering our knowledge of the fabrication of aza heterocycles, we set out to develop a new synthetic protocol for efficient synthesis of polycyclic bis-indoles through a one-pot, two-step, three-component reaction of enaminones 1 and indoles 2 , with acenaphthylene-1,2-dione 3 , and report it herein (Scheme 1).…”