Synthesis of dioxin-like monofluorinated PCBs: for the use as internal standards for PCB analysis

Recent trends in the chemistry of Sandmeyer reaction: a review

Metal-catalyzed reactions play a vital part to construct a variety of pharmaceutically important scaffolds from past few decades. To carry out these reactions under mild conditions with low-cost easily available precursors, various new methodologies have been reported day by day. Sandmeyer reaction is one of these, first discovered by Sandmeyer in 1884. It is a well-known reaction mainly used for the conversion of an aryl amine to an aryl halide in the presence of Cu(I) halide via formation of diazonium salt intermediate. This reaction can be processed with or without copper catalysts for the formation of C-X (X = Cl, Br, I, etc.), C-CF₃/CF₂, C-CN, C-S, etc., linkages. As a result, corresponding aryl halides, trifluoromethylated compounds, aryl nitriles and aryl thioethers can be obtained which are effectively used for the construction of biologically active compounds. This review article discloses various literature reports about Sandmeyer-related transformations developed during 2000-2021 which give different ideas to synthetic chemists about further development of new and efficient protocols for Sandmeyer reaction. An updated compilation of new approaches for Sandmeyer reaction is described in this review to construct a variety of carbon-halogen, carbon-phosphorous, carbon-sulfur, carbon-boron etc. linkages.

Complex of 2-(methylthio)aniline with palladium(II) as an efficient catalyst for Suzuki-Miyaura C-C coupling in eco-friendly water

2-(Methylthio)aniline (L1), a bidentate (S,N) ligand synthesized by the reaction of o-aminothiophenol with methyl iodide, on reacting with Na2PdCl4 in acetone and water gives a complex [PdL1Cl2] (1). Single crystal X-ray diffraction studies have revealed that the geometry of palladium in 1 is nearly square-planar and the ligand L1 is bound to the palladium through S and N in a bidentate coordination mode forming a five membered chelate ring. This complex functions as a thermally and air stable catalyst of high efficiency for Suzuki-Miyaura CC coupling reactions in water. It catalyzes CC coupling between various aryl bromides and phenylboronic acid under mild reaction conditions in water. TON value up to 93,000 has been obtained.

Efficient catalysis of Suzuki-Miyaura C-C coupling reactions with palladium(II) complexes of partially hydrolyzed bisimine ligands: a process important in environment context

Potentially hexadentante [O(-),N,E:E,N,O(-)] chalcogenated bisimine ligands L1-L3 have been synthesized by reaction of 1,1'-(4,6-dihydroxy-1,3-phenylene)bisethanone with H2N(CH2)2SPh, H2N(CH2)2SePh and H2N(CH2)2TeC6H4-4-OMe respectively. The L1-L3 react with Na2PdCl4 resulting in their partial hydrolysis, which appears to be metal-promoted. Of the two [(CH3)CN(CH2)2EAr] fragments of L1-L3, one is converted to (CH3)CO and H2N(CH2)2EAr eliminated. The hydrolysis products 1-[C(CH3)N(CH2)2SPh]-3-[C(CH3)O]-4,6-[OH]2C6H2 (L1'), 1-[C(CH3)N(CH2)2SePh]-3-[C(CH3)O]-4,6-[OH]2C6H2 (L2') and 1-[C(CH3)N(CH2)2TeC6H4-4-OMe]-3-[C(CH3)O]-4,6-[OH]2C6H2 (L3') have formed complexes [PdCl(L'-H)] (1, 3 and 5). The other product of hydrolysis H2N(CH2)2EAr (L″) reacted with Na2PdCl4 yielding the complexes [PdL"Cl2] (2, 4 and 6). All the complexes (1-6) were found thermally and air stable. Complexes 1, 3 and 5 have been investigated as catalysts for Suzuki-Miyaura CC coupling reactions. The catalytic activities of 1 and 3 which are palladium complexes of S- and Se-containing Schiff base derivatives respectively, were found good for the Suzuki-Miyaura cross-coupling of aryl bromides with phenylboronic acid under mild reaction conditions. The Pd(II) complex (3) of selenated ligand was found active to catalyze the coupling of 2-chlorobenzaldehyde and 3-chlorotoluene. The activity of Te analog was found to be the lowest one as it failed in catalyzing the coupling of electronically deactivated aryl bromides.

The analysis of dioxins and related compounds

The analysis of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, polychlorinated biphenyls, and other related compounds requires complex sample preparation and analytical procedures using highly sensitive and selective state-of-the-art instrumentation to meet very stringent data quality objectives. The analytical procedures (extraction, sample preparation), instrumentation (chromatographic separation and detection by mass spectrometry) and screening techniques for the determination of dioxins, furans, dioxin-like polychlorinated biphenyls and related compounds with a focus on new approaches and alternate techniques to standard regulatory methods are reviewed.