We report the use of ruthenium–NNN‐pincer complexes of the type (R2NNN)RuCl2(PPh3) (R = tBu, iPr, Cy and Ph) for the catalytic N‐alkylation of primary amines under solvent‐free conditions. For the first time, the base that is required to promote these reactions is generated in situ from the alcohol by the use of sodium. The resulting sodium alkoxide regenerates the alcohol substrate while acting as the water scavenger thus mitigating the need of an additional base. Among the catalysts screened, (tBu2NNN)RuCl2(PPh3) (0.02 mol‐%) gives very high turnovers and good yields at 140 °C. The (tBu2NNN)RuCl2(PPh3) catalyzed N‐alkylation tolerates a variety of amine and alcohol substrates. While excellent turnover (29000) was obtained for the (tBu2NNN)RuCl2(PPh3) (0.002 mol‐%) catalyzed alkylation of aniline with cyclohexyl methanol, the turnovers obtained in the corresponding catalytic methylation of p‐anisidine was also very high (12000). The (tBu2NNN)RuCl2(PPh3) catalyzed reactions have also been accomplished under open‐vessel conditions resulting in a net dehydrogenative coupling reaction. This protocol has been used to transform benzene‐1,2‐diamines to benzimidazoles with high productivity (12000 turnovers). DFT studies indicate that while β‐hydride elimination is rate‐determining (RDTS: 24.31 kcal/mol) for the alcohol dehydrogenation segment which is endothermic, insertion of the imine is rate‐determining (RDTS: 11.26 kcal/mol) for its hydrogenation that is exothermic.

Polyacetylene bridged π-conjugated polyaromatic hydrocarbons (PAHs) have found wide applications in the fabrication of organic field-effect transistors (OFETs), organic light emitting diodes (OLEDs), solar cells, organic photovoltaic devices (OPV), liquid crystal displays and sensors. The ease with which semiconducting and/or emissive behaviour of polyacetylene bridged PAHs could be modulated by tailored functionalities via state-of-art powerful synthetic tools along with their low production cost and mechanical flexibility makes them one among the favourites for versatile optoelectronic and sensing applications. The current review sheds light on the applicability of Sonogashira coupling in the synthesis of PAHs with alkynyl bridges with particular emphasis on their photophysical properties. The review further discusses the utility of alkynyl bridged PAHs from the point of view of their applications in optoelectronic devices and in sensing nitroaromatics. The rich synthetic Sonogashira coupling that is available at one's disposal along with the promising photophysical properties demonstrated by alkynyl bridged PAHs offers great promise in design of novel πconjugated molecules that are capable of exhibiting exciting optoelectronic and sensing applications.

For the first time a direct single-step one-pot route to access nine new symmetric tetraalkynylated anthracenes via the Pd(CH3CN)2Cl2/ cataCXium®A catalyzed tetra-fold Sonogashira coupling is reported. Five of these tetraalkynylated...

Readily available and inexpensive bromide salt based on earthabundant nickel has been used to catalyze the Suzuki coupling of a variety of aryl halides (ca. 37 examples) in high yields under ambient conditions with good functional group tolerance. The reactivity of various aryl halides follows the corresponding CÀ X (X = I, Br and Cl) bond strength in the order ArÀ I > ArÀ Br > ArÀ Cl. EPR analysis, mercury-drop experiments and reactions with radical scavenger such as TEMPO point to the involvement of well-defined molecular species that operate via a Ni(0)/Ni(II) catalytic cycle where oxidative addition of the aryl halide to Ni(0) is likely to be the rate-determining-step (RDS). For the first time, valuable new polycyclic aromatic hydrocarbons (PAHs) with exciting photophysical properties have been synthesized (ca. 23 examples) via a Ni(II) catalyzed multi-fold Suzuki coupling.

The multifold Sonogashira coupling of a class of aryl halides with arylacetylene in the presence of an equivalent of Cs 2 CO 3 has been accomplished using a combination of Pd(CH 3 CN) 2 Cl 2 (0.5 mol %) and cataCXium A (1 mol %) under copperfree and amine-free conditions in a readily available green solvent at room temperature. The protocol was used to transform several aryl halides and alkynes to the corresponding coupled products in good to excellent yields. The rate-determining step is likely to involve the oxidative addition of Ar-X. The green protocol provides access to various valuable polycyclic aromatic hydrocarbons (PAHs) with exciting photophysical properties. Among them, six tetraalkynylated anthracenes have been tested for their anticancer properties on the human triple-negative breast cancer (TNBC) cell line MDA-MB-231 and human dermal fibroblasts (HDFs). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to find out the IC 50 concentration and lethal dose. The compounds being intrinsically fluorescent, their cellular localization was checked by live cell fluorescence imaging. 4′,6-Diamidino-2-phenylindole (DAPI) and propidium iodide (PI) staining was performed to check apoptosis and necrosis, respectively. All of these studies have shown that anthracene and its derivatives can induce cell death via DNA damage and apoptosis.