The reaction of copper(I) halides with 2-thiouracil (TUC), 6-methyl-2-thiouacil (MTUC), and 4-methyl-2-mercaptopyrimidine (MPMTH) in the presence of triphenylphosphine (tpp) in a 1:1:2 molar ratio results in a mixed-ligand copper(I) complex with the formulas [Cu2(tpp)4(TUC)Cl] (1), [Cu2(tpp)4(MTUC)Cl] (2), [Cu(tpp)2(MPMTH)Cl]·(1)/2CH3OH (3), [Cu(tpp)2(MTUC)Br] (4), and [Cu(tpp)2(MTUC)I]·(1)/2CH3CN (5). The complexes have been characterized by FT-IR, (1)H NMR, and UV-vis spectroscopic techniques and single-crystal X-ray crystallography. Complexes 1 and 2 are binuclear copper(I) complexes. Two phosphorus atoms from tpp ligands are coordinated to the copper(I) ions, forming two units that are linked to each other by a deprotonated TUC or MTUC chelating ligand through a sulfur bridge. A linear Cu-S-Cu moiety is formed. The tetrahedral geometry around the metal centers is completed by the nitrogen-donor atom from the TUC or MTUC ligand for the one unit, while for the other one, it is completed by the chloride anion. Two phosphorus atoms from two tpp ligands, one sulfur atom from MPMTH or MTUC ligand, and one halide anion (Cl, Br, and I) form a tetrahedron around the copper ion in 3-5 and two polymorphic forms of 4 (4a and 4b). In all of the complexes, either mono- or binuclear intramolecular O-H···X hydrogen bonds enhance the stability of the structures. On the other hand, in almost all cases of mononuclear complexes (with the exception of a symmetry-independent molecule in 4a), intermolecular NH···O hydrogen-bonding interactions lead to dimerization. Complexes 1-5 were studied for their catalytic activity for the intermolecular cycloaddition of iodonium ylides toward dihydrofuran formation by HPLC, (1)H NMR, and LC-HRMS spectroscopic techniques. The results show that the geometry and halogen and ligand types have a strong effect on the catalytic properties of the complexes. The highest yield of dihydrofurans was obtained when "linear" complexes 1 and 2 were used as the catalysts. The activity of the metal complexes on the copper(I)-catalyzed and uncatalyzed intramolecular cycloaddition of iodonium ylide is rationalized through electronic structure calculation methods, and the results are compared with the experimental ones.
A cyclic β-dicarbonyl phenyliodonium ylide reacted with various substituted styrenes under Rh2(OAc)4 catalysis to give cyclopropanes and dihydrofurans in a highly regioselective fashion. When styrenes with electron-donating substituents or disubstituted were employed, only dihydrofurans were isolated instead. A mechanism involving two competing pathways rationalizes the results.
Oxindoles bearing ketone side chains in the 3-position can be synthesized by Brønsted acid catalysis from N-aryl methacrylamides, ketones, and hydroperoxides. The cyclized products are presumably formed in a radical cascade reaction, initiated by decay of intermediate alkenyl peroxides. In the case of acrylic substrates that do not undergo cyclization, γ-peroxyketones were isolated instead, indicating that the final cyclization step of the cascade does not take place in these cases.
Synthesis of Oxindoles by Broensted Acid Catalyzed Radical Cascade Addition of Ketones. -N-alkylated methacrylic acid anilides react with ketones via tBuOOH--mediated radical cascade Michael addition/cyclization to the title compounds in good to high yields. Non-alkylated anilide (XIIb) or methacrylic acid phenyl ester (XIIa) do not undergo cyclization but give the peroxylated Michael adducts (XIV). -(BOESS, E.; KARANESTORA, S.; BOSNIDOU, A.-E.; SCHWEITZER-CHAPUT, B.; HASENBECK, M.; KLUSSMANN*, M.; Synlett 26 (2015) 14, 1973-1976, http://dx.doi.org/10.1055/s-0034-1381052 ; MPI Kohlenforsch., D-45470 Muelheim/Ruhr, Germany; Eng.) -M. Tismer 02-112
Metal-Catalyzed Thermal Reactions of Cyclic -Dicarbonyl Phenyliodonium Ylide with Styrenes. -Under conditions B), exclusive formation of dihydrofuran structures takes place in a highly regioselective manner. The product formation under thermal conditions A) depends on the substitution pattern. With styrenes (IIb,d-f), mixtures of dihydrofurans and cyclopropanes are obtained. If the styrene educt is disubstituted or bears electron-donating substituents, only the benzofuran products are formed. -(BOSNIDOU, A.-E.; KALPOGIANNAKI, D.; KARANESTORA, S.; NIXAS, J. A.; HADJIARAPOGLOU*, L. P.; J. Org. Chem. 80 (2015) 2, 1279-1283, http://dx.
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