Synthesis of thiazolidinimines/thiazinan-2-imines via three-component coupling of amines, vic-dihalides and isothiocyanates under metal-free conditions

Copper-Catalyzed One-Pot Synthesis of Thiazolidin-2-imines

The synthesis of thiazolines, thiazolidines, and thiazolidinones has been extensively studied, due to their biological activity related to neurodegenerative diseases, such as Parkinson's and Alzheimer's, as well as their antiparasitic and antihypertensive properties. The closely related thiazolidin-2-imines have been studied less, and efficient strategies for synthesizing them, mainly based on the reaction of propargylamines with isothiocyanates, have been explored less. The use of one-pot approaches, providing modular, straightforward, and sustainable access to these compounds, has also received very little attention. Herein, we report a novel, one-pot, multicomponent, copper-catalyzed reaction among primary amines, ketones, terminal alkynes, and isothiocyanates, toward thiazolidin-2-imines bearing quaternary carbon centers on the five-membered ring, in good to excellent yields. Density functional theory calculations, combined with experimental mechanistic findings, suggest that the copper(I)-catalyzed reaction between the in situ-formed propargylamines and isothiocyanates proceeds with a lower energy barrier in the pathway leading to the S-cyclized product, compared to that of the N-cyclized one, toward the chemo- and regioselective formation of 5-exo-dig S-cyclized thiazolidin-2-imines.

Light-Driven Access to Selenium-Substituted Thiazole-2-imine Derivatives

The thiazole-2-imine derivatives with interesting pharmacological activities have attracted significant attention. However, previously reported synthesis strategies usually suffered from some drawbacks, such as the use of metals/additive and harsh reaction conditions. Herein, we developed a metal- and photoinitiator-free photocatalytic strategy for the synthesis of various selenium-substituted thiazole-2-imine derivatives for the first time. The reaction displayed mild reaction conditions, simple operation, a broad substrate scope (37 examples), and good to excellent yields.

BF3·Et2O catalyzed transannulation of pyridotriazoles with isothiocyanates: synthesis of thiazolo[3,4-a]pyridin-3-imines

The synthesis of thiazolo[3,4-a]pyridin-3-imines, through denitrogenative transannulation of pyridotriazoles, under transition metal-free conditions is described.