Chemodivergent Photocatalyzed Heterocyclization of Hydrazones and Isothiocyanates for the Selectivity Synthesis of 2-Amino-1,3,4-thiadiazoles and 1,2,4-Triazole-3-thiones

Abstract

A photocatalytic chemodivergent reaction for the selectivity formation of C–S and C–N bonds in a controlled manner was proposed. The reaction medium, either neutral or acidic, is critical to dictate the formation of 2-amino-1,3,4-thiadiazoles and 1,2,4-triazole-3-thiones from isothiocyanates and hydrazones. This is a practical protocol to achieve the chemoselectivity under mild and metal-free conditions.

Biological Evaluation of Anti‐Cholinesterase Activity, in Silico Molecular Docking Studies, and DFT Calculations of Green Synthesized Thiadiazolo[3,2‐a]pyrimidine Derivatives

“…By studying on the mechanism of the reaction and how 2amino-1,3,4-thiadiazoles behave differently from ordinary amines, we noticed that 2-amino-1,3,4-thiadiazoles, despite their aromatic character, can do electrophilic attack using their rind nitrogen atoms and this can be achieved through tautomerization of the ring, which contribute to their remarkable pathways of reactivity (Scheme 2). [59] Based on our experimental results and literature reports, [48,60] a probable mechanism is proposed for the synthesis of target compounds 4a-j in the presence of FeCl 3 catalyst (Scheme 3). The reaction is accrued via a common Knoevenagel condensation between ethyl acetoacetate 2 and aromatic aldehyde 3 to form intermediate A in the presence of FeCl 3.…”

“…By studying on the mechanism of the reaction and how 2‐amino‐1,3,4‐thiadiazoles behave differently from ordinary amines, we noticed that 2‐amino‐1,3,4‐thiadiazoles, despite their aromatic character, can do electrophilic attack using their rind nitrogen atoms and this can be achieved through tautomerization of the ring, which contribute to their remarkable pathways of reactivity (Scheme 2). [59] …”

Light-assisted green and efficient construction of thiadiazole/selenadiazole derivatives

“…As a consequence, the design and development of interesting approaches for the construction of 1,3,4-thiadiazole/selenadiazole backbones are of great significance and have attracted a great deal of attention. 14–16…”

“…17–20 The most popular strategies for constructing a 1,3,4-thiadiazole structural framework involve sulfonyl hydrazide or hydrazine and sulfur-containing substances such as CS 2 , KSCN, and Lawesson or Woollin reagents, together with carboxylic acid. 14–18 The routes for the formation of 1,3,4-selenadiazole are usually similar to those for 1,3,4-thiadiazole 12,13,19,20 by replacing sulphur-containing reactants with selenium-containing reagents.…”