Ruthenium(II)-Catalyzed ortho-C–H Chalcogenation of Benzoic Acids via Weak O-Coordination: Synthesis of Chalcogenoxanthones

Abstract

A general protocol for direct chalcogenation of inert C-H bonds of (hetero)aromatic carboxylic acids is developed with a ruthenium(II) catalyst using readily available starting materials, offering densely substituted ortho-chalcogenyl aromatic acids in high yields (up to 96%). The strategy avoids the installation of an external directing group, use of metallic oxidants, and features operational simplicity with ample substrate scope. Synthetic application en route to biologically important chalcogenoxanthones is also demonstrated. This work represents the first example of ruthenium(II)-catalyzed direct C-H chalcogenation of benzoic acids.

Rhodium‐Catalyzed Direct and Selective ortho C−H Chalcogenation of N‐(Hetero)aryl‐7‐azaindoles

“…Recently, various transition metal catalyzed chelation‐assisted C−H chalcogeno‐ether formation reactions has emerged as a powerful and alternative tool . Such synthetic protocols have been devised employing various directing groups such as pyridine, amide, oxime, pyrimidine, acid and various bidentate auxiliaries. Considering the outstanding importance of pharmacophore nature of azaindole and organo‐chalcogen compounds, we envisaged that a catalytic approach for the direct and selective C−H thiolation/selenylation of azaindole could be highly attractive.…”

“…As part of our program to develop metal catalyzed C−H bond functionalization of 7‐azaindoles,, we wish to report N‐directed selective and efficient C−H ortho ‐sulfenylation/selenylation, of the pharmaceutically important scaffold N ‐aryl‐7‐azaindole using [Cp*RhCl 2 ] 2 catalyst in presence of additives AgOTf, Ag 2 CO 3 in 1,4‐dioxane and easily accessible disulfide as the sulfur source.…”

BINOL accelerated Ru(II)-catalyzed regioselective C-H functionalization of arenes with disulfides and diselenides

“…6 In 2006, Yu and co-workers demonstrated a Cu-catalyzed C-H thiolation of 2-phenylpyridines utilizing disulfides. 7a Since then, efforts are made on the directing group assisted C-H functionalization of arenes with disulfides using Cu, 7 Co, 8 Ni, 9 Rh, 10 Ru 11 and Pd 12 -based catalytic systems. 7-Azaindoles are important structural scaffolds found in a plethora of bioactive natural products and marketed drugs.…”

Ruthenium(II)‐Catalyzed C−H Chalcogenation of Anilides

“…While these protocols provided efficient and convenient routes to access various chalcogenated arenes, there are still some restrictions, such as long reaction time as well as harsh reaction conditions that may limit further applications. [15] Anilides are useful building blocks in organic synthesis, medicinal chemistry, natural products and drug discovery. [15] Anilides are useful building blocks in organic synthesis, medicinal chemistry, natural products and drug discovery.…”