Novel iodine-induced sulfonylation and sulfenylation of imidazopyridines have been described using sodium sulfinates as the sulfur source. This strategy enables highly selective difunctionalization of imidazo[1,2-a]pyridine to access sulfones and sulfides in good yields. A wide range of substrates and functional groups were well-tolerated under optimized conditions. Moreover, control experiments have been conducted, indicating a radical pathway involved in the reaction mechanisms.

C−H functionalization has been established as a powerful strategy for the commercial construction of organic molecules. This review encompasses the most recent advances in C−H activation catalyzed by earth‐abundant cobalt complexes, involving two types of fundamental reaction paths, that is, the concerted metalation–deprotonation (CMD) path associated with non‐oxidative C−H activation and the intermolecular single‐electron‐transfer (SET) path. Transformations catalyzed by high‐valent cobalt based on the two mechanisms and used in organic syntheses, including those involving C−C and C−X (X=O and N) bond formation, are herein presented.

A series of novel ruthenium(II) complexes supported by a symmetrical NNN ligand were prepared and fully characterized. These complexes exhibited good performance in transfer hydrogenation to form new C-C bonds using alcohols as the alkylating agents, generating water as the only byproduct. A broad range of substrates, including (hetero)aryl- or alkyl-ketones and alcohols, were well tolerated under the optimized conditions. Notably, α-substituted methylene ketones were also investigated, which afforded α-branched steric hindrance products. A potential application of α-alkylation of methylene acetone to synthesize donepezil was demonstrated, which provided the desired product in 83% yield. Finally, this catalytic system could be applied to a one-pot double alkylation procedure with sequential addition of two different alcohols. The current protocol is featured with several characteristics, including a broad substrate scope, low catalyst (0.50 mol %) loadings, and environmental benignity.

A new cobalt(II)-catalyzed decarboxylative C-H activation/annulation of benzamides and alkynyl carboxylic acids has been described. Alkynyl carboxylic acids were first employed as the coupling partners using inexpensive Co(OAc)2·4H2O as the catalyst. This method enables a switchable cyclization to isoquinolones and isoindolinones with excellent selectivity. Moreover, a catalytic amount of Ag2O was adopted as co-catalyst and O2 (from air) as a terminal oxidant for the preparation of isoquinolones.

Co(II)-catalyzed C-H C2 selective arylation of indoles with boronic acids through monodentate chelation assistance has been achieved for the first time. The unique features of this methodology include mild reaction conditions, highly C2 regioselectivity, and employment of a Grignard reagent-free catalytic system. A wide range of substrates, including unreactive arenes, are well tolerated, which enables the construction of the coupling products efficiently. This new strategy provides an alternative and versatile approach to construct biaryls using inexpensive cobalt catalyst.

Sonogashira‐Kreuzkupplung eines Dibromcyclopenta[hi]aceanthrylens mit einem Diethinylfluoren ergibt ein Donor‐Akzeptor‐Copolymer, das ausschließlich cyclopentaanellierte polycyclische Arensysteme enthält. Das Polymer hat eine kleine Bandlücke (<1.5 eV), zeigt zwei Absorptionsbanden und wirkt als Elektronenakzeptor, wie die Fluoreszenzlöschung von Poly(3‐hexylthiophen) belegt.

As a powerful synthetic tool for the formation of aromatic C−N bonds, the reported transition-metalcatalyzed direct C−H amination has been ineffective for the synthesis of triarylamines for a long time. Herein, an elegant strategy for the preparation of triarylamines was disclosed using inexpensive Co(OAc) 2 •4H 2 O as the catalyst. It is noteworthy that unactivated arenes and simple anilines were employed as the starting materials with good functional group tolerance. In addition, an organometallic Co(III) species was isolated and identified by X-ray crystallography, thus providing some in-depth insights into the mechanism.

A series of alternating copolymers containing oligomeric bis(2-ethylhexyl)-p-phenylenevinylene (BEH-PPV) chromophores and conformational-flexible n-decyl or tetraethylene glycol chains were prepared. The polymerization was carried out using Sonogashira coupling conditions between monomers composed of an iodo-terminated PPV oligomer (trimer, pentamer, or septamer) and a bis(phenylacetylene)-containing flexible chain. Polymers containing the n-decyl chain attained higher molecular weights compared to the tetraethylene glycol-containing polymers. 4-Ethynylanisole-capped oligomers (trimer, pentamer, or septamer) were prepared, and their solution photophysical properties were compared to the analogous polymeric materials. The solution optical properties of the polymers were primarily determined by chromophore length of the constituent oligomers. In contrast, the thin film fluorescence spectra of the polymers showed substantial differences between n-decyl and tetraethylene glycol containing materials, suggesting significant changes in the degree of interchain coupling in the solid state. The control of effective conjugation length afforded by these materials makes them a promising system for understanding electronic trap states in conjugated polymers.