Ruthenium(ii)-catalyzed C–O/C–S cyclization for the synthesis of 5-membered O-containing and S-containing heterocycles

Abstract

An efficient and convenient method for the synthesis of oxazole derivatives from enamides has been established via a ruthenium-catalyzed C–O cyclization.

Reactivity of (Z)-4-Aryliden-5(4H)-thiazolones: [2 + 2]-Photocycloaddition, Ring-Opening Reactions, and Influence of the Lewis Acid BF3

“…In that case, the reaction was performed using NaOH in water to afford the corresponding carboxylic acid . Dihydrothiazoles are interesting materials due to their properties, and different synthetic methods have been reported for their preparation, most of them starting from aminothiols. − Dihydrothiazoles are versatile intermediates for the synthesis of high-value-added compounds, for instance β-cysteine and derivatives, − are present in flavours and in natural products, − and show a remarkable pharmacological activity. − For all of these reasons, we decided to explore this almost unprecedented synthesis of dihydrothiazoles from thiazolones 2 in more detail. The results are presented in Figure .…”

Ruthenium Catalyzed Intramolecular C−X (X=C, N, O, S) Bond Formation via C−H Functionalization: An Overview

“…Hu and co‐workers in 2019 disclosed an efficient protocol for the preparation of substituted oxazoles via ruthenium‐catalyzed C−H functionalization (Scheme 42). [61] This oxidative annulation strategy allows an extensive functional group tolerance, broad substrate scope with operational simplicity. Apart from the oxazole ring, other 5‐member heterocycles, such as furan and thiazole scaffolds, could also be obtained using an appropriate substrate(s) via C−O/C−S bond cyclization with the ruthenium catalyst in the presence of an oxidant.…”

Copper-Catalyzed Chemodivergent Synthesis of Oxazoles and Imidazolidones by Selective C–O/C–N Cyclization

“…Recently, transition-metal-catalyzed reactions have emerged as a more step- and atom-economical strategy for the synthesis of molecular entities, providing an efficient approach to access oxazole and imidazole compounds . For example, Pd-catalyzed oxidative cyclization of O -acyl cyanohydrins/ N -acyl enamides, Rh-catalyzed annulation of oximes and diazo esters, Co-catalyzed radical aza-Heck amination of allyl alcohols, Cu-mediated aerobic oxidative reactions, ,, Au-catalyzed cyclization synthesis of trisubstituted oxazoles, and other reactions. − In imidazole synthesis, the classic method uses the Debus–Radziszewski reaction . Recent progress has been published in the synthesis of imidazoles by cyclization reaction of oxime esters, ketones, − and azides. − …”

“…Notwithstanding the major advances that have been achieved in the synthesis of derivatives of oxazole and imidazole, the methods reported typically rely on noble-metal catalysts, multistep synthesis, harsh reaction conditions, low atom economy, or relatively inaccessible starting materials. ,, Therefore, development of a versatile and practical strategy to construct heterocyclic molecules efficiently and economically from readily available and commercial building blocks is desirable. Herein, we report a copper-catalyzed oxidative method for the chemodivergent synthesis of diverse heterocyclic core scaffolds derived from phenylalanine or its derivatives (Figure b).…”