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Volumn , Issue 16, 2007, Pages 2579-2583

Palladium-doped mixed oxides as 'slow-release' catalysts for suzuki couplings

Author keywords

Boronic acids; Cross couplings; Microwave irradiation; Sol gel catalysts; Suzuki couplings

Indexed keywords

BORONIC ACID DERIVATIVE; OXIDE; PALLADIUM;

EID: 35348969025     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-2007-986639     Document Type: Article
Times cited : (23)

References (48)
  • 4
    • 11244296859 scopus 로고    scopus 로고
    • 2nd ed, de Meijere, A, Diederich, F, Eds, Wiley-VCH: Weinheim, and references cited therein
    • (d) Miyaura, N. In Metal-Catalyzed Cross-Coupling Reactions, 2nd ed.; de Meijere, A.; Diederich, F., Eds.; Wiley-VCH: Weinheim, 2004, 41; and references cited therein.
    • (2004) Metal-Catalyzed Cross-Coupling Reactions , pp. 41
    • Miyaura, N.1
  • 22
    • 33846893890 scopus 로고    scopus 로고
    • and references cited therein
    • (d) Yin, L.; Liebscher, J. Chem. Rev. 2007, 107, 133; and references cited therein.
    • (2007) Chem. Rev , vol.107 , pp. 133
    • Yin, L.1    Liebscher, J.2
  • 32
    • 35349008727 scopus 로고    scopus 로고
    • Preparation of Catalysts: The catalysts were prepared by a modified sol-gel method. The following precursors, Cu(N03) 2·3H2O, Fe(NO3)3· 9H2O, La(NO3)3·6H2O, Ni(NO3)2·6H2O, and Pd(NO 3)2·H2O, were dissolved in distilled H2O and mixed with ethylene glycol and nitric acid. The molar ratio was M/H2O/ethylene glycol/HNO3, 1:40:20:4 M as the sum of metal ions, The solutions were dried and calcined in air for 12 h at 80°C, for 60 h at 105°C and for 5 h at 400°C with a heating rate of 6°C/h each. After calcination the powders were ground and sieved
    • 3 = 1:40:20:4 (M as the sum of metal ions). The solutions were dried and calcined in air for 12 h at 80°C, for 60 h at 105°C and for 5 h at 400°C with a heating rate of 6°C/h each. After calcination the powders were ground and sieved.
  • 36
    • 35349007123 scopus 로고    scopus 로고
    • General Procedure for Suzuki Couplings in EtOH-Toluene: To a two-phase system of toluene (4 mL, EtOH (1.3 mL) and 2 M K2CO 3 (2 mL, aryl halide (1.0 mmol, boronic acid (1.1 mmol) and catalyst (for mol% of Pd see Table 1) were added and the mixture was heated to reflux for the specified time. After cooling to r.t, H2O was added and the aqueous layer was extracted with Et2O (3 x, After drying (Na2SO4) and evaporation of the solvent, the crude product was purified by column chromatography (silica gel, hexanes-EtOAc, 4-Benzyloxy-4′-methoxybiphenyl (3, According to this general procedure 3 was obtained from 4-bromoanisole (187 mg) and 4- benzyloxyphenylboronic acid (251 mg) as a white solid; mp 170°C. 1H NMR (500 Hz, CDCl3, δ, 7.45 (m, 6 H, 7.40 (dd, J, 7.3, 7.7 Hz, 2 H, 7.34 (t, J, 7.3 Hz, 1 H, 7.04 (d, J, 8.7 Hz, 2 H, 6.96 d, J
    • 2: 290.1307; found: 290.1340.
  • 41
    • 35348985068 scopus 로고    scopus 로고
    • General Procedure for Suzuki-Couplings in Water under Microwave Irradiation: In a glass tube were placed aryl halide (1 mmol, phenylboronic acid (183 mg, 1.5 mmol, catalyst (1.2 mol, 2 M K2CO3 (2 mL) and H2O (4 mL, The sealed vessel was placed into the microwave. The mixture was irradiated in a sealed tube at 150°C (initial power 100 W, After 60 min the reaction was cooled to r.t. Then H2O was added and the aqueous layer was extracted with Et2O (3 x, After drying (Na2SO4) and evaporation of the solvent, the crude product was purified by column chromatography (silica gel, hexanes-EtOAc, 4-Nitrobiphenyl (8a, yellow solid; mp 112°C 1H NMR (500 Hz, CDCl3, δ, 8.30 (d, J, 8.9 Hz, 2 H, 7.74 (d, J, 8.9 Hz, 2 H, 7.63 (d, J, 7.1 Hz, 2 H, 7.50 (dd, J, 7.1, 7.5 Hz, 2 H, 7.45 (t, J, 7.5 Hz, 1 H, 13C NMR 500
    • 3): δ =191.8, 147.1, 139.6, 135.1, 130.2, 128.9, 128.4, 127.6, 127.3.
  • 43
    • 35348939274 scopus 로고    scopus 로고
    • 139La. Calibration was carried out with external standards of 10 ppt, 100 ppt, 1 ppb, 2 ppb, 5 ppb, 10 ppb and 100 ppb palladium and lanthanum. The freshly irradiated (100 W, 150°C, 1 h) and filtered solution of catalyst C was diluted to 1:20, 1:30, 1:100 and 1:200. A 3% nitric acid solution was added to all samples. The average of the Pd and La concentrations in solution was calculated from these acquired concentrations.
    • 139La. Calibration was carried out with external standards of 10 ppt, 100 ppt, 1 ppb, 2 ppb, 5 ppb, 10 ppb and 100 ppb palladium and lanthanum. The freshly irradiated (100 W, 150°C, 1 h) and filtered solution of catalyst C was diluted to 1:20, 1:30, 1:100 and 1:200. A 3% nitric acid solution was added to all samples. The average of the Pd and La concentrations in solution was calculated from these acquired concentrations.


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