This paper describes a new reactivity of the Pd-catalyzed coupling of 2-amino-3-bromo-aromatic and heteroaromatic compounds with sulfonylhydrazones (Barluenga reaction).The new catalyst system and modulation of the electronic nature of hydrazone that were needed for successful reaction are described herein.

Nanostructured carbon black (CB) was first employed directly in this paper for the simultaneous electrochemical determination of trace Pb(II) and Cd(II) using differential pulse anodic stripping voltammetry. The morphology and surface properties of conductive CB were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy and Raman spectroscopy. Special pore structures, as well as surface chemical functional groups, endow CB with excellent catalytic and adsorption properties. Some parameters affecting electrical analysis performance were investigated systematically including deposition time and potential, pH value of solution, volume of suspension, amount of Bi(III) and Nafion solution. CB–Nafion–glassy carbon electrode sensor linear response ranges from 6 to 1000 nM for selective and simultaneous determination. The detection limits were calculated to be 8 nM (0.9 µg l−1) for Cd(II) and 5 nM (1.0 µg l−1) for Pb(II) (S/N = 3) for the electrocatalytic determination under optimized conditions. The method was successfully used to the determination of actual samples and good recovery was achieved from different spiked samples. Low detection limits and good stability of the modified electrode demonstrated a promising perspective for the detection of trace metal ions in practical application.

Abstract:The carboxylate anion has been used as a directing group in the aromatic amination of electronically equivalent aryl bromides to afford selective ortho-substituted derivatives (> 99:1 selectivity; 60-80% yield) in the case of copper(I) catalysis. The solvent, base and equivalents of base were important factors in the success of this reaction. Complementary selectivity was achieved with palladium catalysis where the para-substituted derivatives were produced selectively (> 99% selectivity, 70-80% yield).

A novel reactivity of sulfonylhydrazones under Pd catalysis is described, where SO2 and N2 are formally extruded to afford the product of an apparent internal coupling reaction. The reaction is effective with both carbocyclic and heterocyclic aromatic precursors.

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