β‑Arylation of Carboxamides via Iron-Catalyzed C(sp³)–H Bond Activation

A 2,2-disubstituted propionamide bearing an 8-aminoquinolinyl group as the amide moiety can be arylated at the β-methyl position with an organozinc reagent in the presence of an organic oxidant, a catalytic amount of an iron salt, and a biphosphine ligand at 50 °C. Various features of selectivity and reactivity suggest the formation of an organometallic intermediate via rate-determining C–H bond cleavage rather than a free-radical-type reaction pathway

Pyrophosphate-Induced Intramolecular Excimer Formation in Dinuclear Zinc(II) Complexes with Tetrakisquinoline Ligands

Dinuclear Zn²⁺ complexes with HTQHPN (<i>N,N,N</i>′<i>,N</i>′-tetrakis­(2-quinolylmethyl)-2-hydroxy-1,3-propanediamine) derivatives have been prepared, and their pyrophosphate (PPi, P₂O₇^4–) sensing properties were examined. The ligand library includes six HTQHPN derivatives with electron-donating/withdrawing substituents, an extended aromatic ring, and six-membered chelates upon zinc binding. Complexation of ligand with 2 equiv of Zn²⁺ promotes small to moderate fluorescence enhancement around 380 nm, but in the cases of HTQHPN, HT­(6-FQ)­HPN (<i>N,N,N</i>′<i>,N</i>′-tetrakis­(6-fluoro-2-quinolylmethyl)-2-hydroxy-1,3-propanediamine), and HT­(8Q)­HPN (<i>N,N,N</i>′<i>,N</i>′-tetrakis­(8-quinolylmethyl)-2-hydroxy-1,3-propanediamine), subsequent addition of PPi induced a significant fluorescence increase around 450 nm. This fluorescence enhancement in the long-wavelength region is attributed to the conformational change of the bis-(quinolylmethyl)­amine moiety which promotes intramolecular excimer formation between adjacent quinolines upon binding with PPi. The structures of PPi- and phosphate-bound dizinc complexes were revealed by X-ray crystallography utilizing phenyl-substituted analogues. The zinc complex with HT­(8Q)­HPN exhibits the highest signal enhancement (<i>I</i>_PPi/<i>I</i>₀ = 12.5) and selectivity toward PPi sensing (<i>I</i>_ATP/<i>I</i>_PPi = 20% and <i>I</i>_ADP/<i>I</i>_PPi = 25%). The fluorescence enhancement turned to decrease gradually after the addition of more than 1 equiv of PPi due to the removal of zinc ion from the ligand–zinc–PPi ternary complex, allowing the accurate determination of PPi concentrations at the fluorescence maximum composition. The practical application of the present method was demonstrated monitoring the enzymatic activity of pyrophosphatase

Asymmetric Autocatalysis Initiated by Finite Single-Wall Carbon Nanotube Molecules with Helical Chirality

An asymmetric autocatalysis reaction was initiated by a finite single-wall carbon nanotube molecule with helical chirality. The asymmetric induction was initiated by the chiral environment arising from the planar chirality of the tubular polyaromatic hydrocarbons