Substrate-Directed C-H Functionalization of 2-Aryl Pyridines by Transition Metal Complexes

International audienceTransition metal mediated C-H activation is a powerful synthetic tool for the total synthesis of complex natural products and biologically active molecules. The strategy involves mainly C-H activation, nucleophilic addition and regeneration of the catalyst. It proceeds through a C-H bond cleavage by ligand coordination to transition metal. Transition metals like Pd, Rh, Ru, Co, and Ir are the most often used catalysts, which form a complex with 2-aryl pyridine and facilitates the functionalization of various C-H bonds to generate diverse C-C and C-X bonds under typically mild reaction conditions with low catalyst loading. In particular, the chelation-assisted cleavage of C-H bonds at ortho-position of the pyridine directing group has been recognized as one of the most powerful strategies for the functionalization of unreactive C-H bonds. Recently, transition metal catalyzed C-H bond activation has received significant interest because it does not require the prefunctionalization of the substrate. Therefore, the metal-catalyzed C-H activation and functionalization is currently considered as atom economy and simplified procedure in comparison with the traditional strategies

Green protocol for conjugate addition of amines to p-quinones accelerated by water

Amines undergo smooth conjugate addition to p-quinones in H2O at ambient temperature in the absence of a catalyst to produce 2-aminoquinones in excellent yields. Significant rate acceleration of this reaction is observed in H2O compared to organic solvents. H2O played a dual role in simultaneously activating the p-quinone and amine. This new methodology constitutes an easy, highly efficient, and green synthesis of substituted p-quinones

Iodine/EtOH: a novel and versatile catalyst for the synthesis of β-amino ketones via three component reaction

A variety of β-amino ketones are readily prepared in high yields and with good to excellent anti selectivity under extremely mild conditions by means of three component coupling of aromatic aldehydes, aryl amines and ketones using 10 mol% of molecular iodine in ethanol. The use of readily available iodine makes this process quite simple, more convenient and cost-effective