RESUMO
Quinoxalinones are a privileged class of compounds, and their structural framework is found in many bioactive compounds, natural compounds, and pharmaceuticals. Quinoxalinone is a promising scaffold for different types of functionalization, and the slight modification of the quinoxalinone skeleton is known to offer a wide range of compounds for drug discovery. Owing to the importance of the quinoxalinone scaffold, we have developed a base-mediated protocol for the C3-alkylation of quinoxalinone followed by tandem cyclization to access novel types of strenuous and fused dihalo-aziridino-quinoxalinone heterocycles via the construction of C-C and C-N bonds. The protocol proved to be simple and practical to access desired fused quinoxalinone heterocycles in excellent yields (up to 98% yield). As an application, the highly functionalized fused dihalo-aziridino-quinoxalinone molecule has been further utilized for mono-dehalogenation under visible light irradiation and selective amide reduction. Moreover, the protocol has also been demonstrated on a gram scale.
Assuntos
Descoberta de Drogas , Ciclização , AlquilaçãoRESUMO
The cyanation of organic compounds is an important synthetic transformation and mainly relies on a toxic CN source. Undeniably, thiocyanate salt has emerged as a very mild and environmentally benign CN source, yet its synthetic utility for cyanation is highly limited to very few types of organic compounds. Herein, we report the direct cyanation of cyclic thioacetals for accessing compounds with two different functional groups (thiocyano-thioesters) in one pot using sodium thiocyanate via photoredox catalysis. The protocol has been further extended for the direct cyanation of disulfides and diselenide to access aryl thiocyanates and aryl selenocyanate. A plausible mechanism has been proposed based on a series of control experiments, cyclic voltammetry and Stern-Volmer studies.
Assuntos
Nitrilas , Tiocianatos , Catálise , Cianatos/química , Dissulfetos , Compostos de Selênio/químicaRESUMO
A visible light-mediated, metal-free, regioselective dihydrothionation of terminal aromatic as well as heteroaromatic alkynes has been achieved using Eosin Y as a photoredox catalyst at room temperature. The protocol gives direct access to different 1,3-dithiolanes under neutral and mild reaction conditions without the use of any base or additives. The electron-donating, electron-withdrawing and electron-deactivating groups tolerated the photocatalytic reaction conditions. The control experiments, cyclic voltammetry, and Stern-Volmer experiment were carried out to gain an insight into the mechanistic pathway. The protocol proved to be scalable at the gram level and also for practicality the deprotection of 1,3-dithiolanes has been demonstrated. The method uses clean energy under sustainable conditions.