912. Metal ions and complexes in organic reactions. Part IV. Copper-promoted preparations of diaryl ethers and completing hydrogen-transfer processes

Abstract

Bacon and Stewart 4953 912. Metal Ions and Complexes in Organic Reactions. Part I V.l Copper-promoted Preparations of Diaryl Ethers and Competing Hydrogen-transfer Processes By R. G. R. BACON and 0. J. STEWART Diaryl ethers have been prepared, e.g. in collidine or dimethylacetamide solution at -170", by the reaction: 2ArHal-t 2Ar'OH + Cu,Oin which a suspension of copper(1) oxide functions as reagent and catalyst; copper or copper(I1) oxide may also be used. The process has preparative value and may be superior to the conventional Ullmann condensation. With an alkali-metal phenoxide the copper oxide is not consumed and reaction may be faster than with the phenol, particularly in dimethylacetamide. Pronounced solvent effects were observed. Halide reactivity was in the order ArI > ArBr > ArCl. Substituent effects were studied.Copper-catalysed substitutive reduction, &Hal --+ ArH, was a common competing reaction] and was sometimes a major effect with an efficient hydrogen acceptor, e.g., o-bromonitrobenzene, or with an efficient hydrogen donor, e.g., o-nitrophenol. Sources of transferred hydrogen may be a substituent group, e.g., OH or NH,, or an aromatic or heterocyclic nucleus. Other side-reactions included decarboxylation, halogen exchange] coupling of the halide to a biaryl, and substitution of the halide by a nucleophile other than the phenol.ULLMANN and his co-workers discovered2 that small amounts of copper catalyse the formation of diary1 ethers in the reaction:

Synthesis of an acyclic diselenodithioether ligand tethered with bulky substituents and its application to the synthesis of a distorted octahedral palladium(II) complex

“…Coupling reaction of 4 with 1,2-diiodobenzene using Cu 2 O in refluxing 2,4,6-trimethylpyridine [6,13] afforded sulfide 5 in 63% yield. Further coupling reaction of 5 with 0.5 equivalents of 1,2-benzenedithiol under the conditions similar to those for the transformation of 4 to 5 gave the expected diselenodithioether 3 in a good yield.…”

“…(1)). The structure of 6 was fully established by 1 H, 13 C, and 77 Se NMR spectrometry, MS, elemental analysis, and single crystal X-ray diffraction.…”

“…Diselenodithioether ligand 3 was characterized on the basis of the 1 H, 13 C, and 77 Se NMR spectroscopic data together with the results of MS measurement and elemental analysis. The molecular structure of 3 in the crystalline state was definitively determined by X-ray structural analysis.…”

“…Short column chromatography was performed with Nacalai Tesque Silica Gel 60. The 1 H NMR (300 MHz) and 13 C NMR (75 MHz) spectra were measured in CDCl 3 with a JEOL AL-300 spectrometer using CHCl 3 (7.25 ppm) as internal standards for 1 H NMR spectroscopy, and CDCl 3 (77.0 ppm) as those for 13 C NMR spectroscopy. The 77 Se NMR (95 MHz) spectra were measured in CDCl 3 or C 2 D 2 Cl 4 with a JEOL JNM AL-300 spectrometer using diphenyl diselenide (460 ppm) as an external standard.…”

Substituent effects on benzyl radical hyperfine coupling constants. Part 2. The effect of sulphur substituents

“…This ether was prepared by the metbod of Bacon and Stewart (23). A mixture of 4-cresol (10.8 g, 0.1 mol), bromobenzene (7.85 g, 0.05 mol), and cuprous oxide (7.15 g. 0.05 mol) in 2,4,6-trimethylpyridine (25 mL) was refluxed for 48 h. The mixture was poured into 6 M HCI (200 mL) and extracted with ether (2 X 200 mL).…”