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Synlett 2009(15): 2457-2460  
DOI: 10.1055/s-0029-1217822
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Copper(I)-Catalyzed C-C and C-O Coupling Reactions Using Hydrazone ­Ligands

Takashi Mino*, Fumitoshi Yagishita, Masanori Shibuya, Kenji Kajiwara, Hiroaki Shindo, Masami Sakamoto, Tsutomu Fujita
Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, ­Chiba 263-8522, Japan
Fax: +81(43)2903401; e-Mail: tmino@faculty.chiba-u.jp;
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Publikationsverlauf

Received 29 May 2009
Publikationsdatum:
17. August 2009 (online)

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Abstract

Copper-catalyzed C-C coupling reaction of aryl iodides with diethylmalonate in toluene at 90 ˚C gave arylated malonates using 5 mol% of CuI with hydrazone 1a as a ligand in good yields under an aerobic atmosphere. We also found CuI/hydrazone 1b in toluene to be an efficient catalytic system for C-O coupling reactions of aryl bromides with phenols to give aryl ethers in good yields at 110 ˚C under an aerobic atmosphere.

Key words

copper catalyst - hydrazone - C-C coupling - C-O coupling - malonate - aryl ether

8

We tried the reaction at 110 ˚C in toluene for 24 h, however, the yield of 2a decreased to 28% and ethyl phenylacetate was also obtained (8% NMR yield).

9

General procedure for copper-catalyzed C-arylation of diethyl malonate with aryl iodides (Table 2): Under an atmosphere of air, aryl iodide (2.0 mmol) was added to a mixture of diethyl malonate (4.0 mmol), Cs2CO3 (4.0 mmol), ligand 1a (0.20 mmol), and CuI (0.10 mmol) in toluene (2 mL) at r.t. The mixture was stirred at 90 ˚C for 24 h, then diluted with EtOAc and H2O. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. The resulting residue was purified by silica gel chromatography (hexane-EtOAc) to provide the desired product. All prepared compounds 2, except 2f, were previously known and identified by ¹H NMR, ¹³C NMR and MS.
Compound 2f (Table  [²] , entry 6): Yield: 53%; brown liquid; ¹H NMR (CDCl3): δ = 1.26 (t, J = 7.1 Hz, 6 H), 2.35 (s, 3 H), 4.16-4.27 (m, 4 H), 4.57 (s, 1 H), 7.13-7.28 (m, 4 H); ¹³C NMR (CDCl3): δ = 14.0, 21.4, 57.9, 61.7, 126.3, 128.4, 128.9, 129.9, 132.6, 138.2, 168.2; EI-MS: m/z (%) = 250 (25) [M+]; HRMS (FAB-MS): m/z calcd for C14H19O4: 251.1283; found: 251.1284.

11

General procedure for copper-catalyzed O-arylation of phenols with aryl bromides (Table 4): Under an atmosphere of air, aryl bromide (0.5 mmol) was added to a mixture of phenol (1.0 mmol), K3PO4 (1.0 mmol), ligand 1b (0.025 mmol), and CuI (0.025 mmol) in toluene (1 mL) at r.t. The mixture was stirred at 110 ˚C for either 5 h or 18 h, then the mixture was diluted with EtOAc and H2O. The organic layer was washed with brine, dried over MgSO4, and concentrated under reduced pressure. The resulting residue was purified by silica gel chromatography (hexane-EtOAc) to provide the desired product. All prepared compounds 3, except 3g and 3h, were known and identified by ¹H NMR, ¹³C NMR and MS.
Compound 3g (Table  [4] , entry 7): Yield: 74%; colorless oil; ¹H NMR (CDCl3): δ = 2.34 (s, 3 H), 6.88 (d, J = 7.6 Hz, 2 H), 6.94-6.97 (m, 2 H), 7.15 (d, J = 8.6 Hz, 2 H), 7.35 (t, J = 8.0 Hz, 1 H), 7.45-7.54 (m, 2 H), 7.58 (d, J = 8.2 Hz, 1 H), 7.84-7.87 (m, 1 H), 8.22-8.25 (m, 1 H); ¹³C NMR (CDCl3): δ = 20.7, 112.6, 118.8, 122.1, 122.9, 125.8, 125.8, 126.5, 126.7, 127.7, 130.3, 132.8, 134.9, 153.6, 155.3; EI-MS: m/z (%) = 234 (100) [M+]; HRMS (FAB-MS): m/z calcd for C17H14O: 234.1045; found: 234.1027.
Compound 3h (Table  [4] , entry 8): Yield: 78%; colorless oil; ¹H NMR (CDCl3): δ = 2.31 (s, 3 H), 2.33 (s, 3 H), 6.77-6.80 (m, 2 H), 6.87-6.93 (m, 3 H), 7.12-7.21 (m, 3 H); ¹³C NMR (CDCl3): δ = 20.7, 21.4, 115.3, 119.0, 119.1, 123.6, 129.3, 130.2, 132.7, 140.0, 154.8, 157.7; EI-MS: m/z (%) = 198 (100) [M+]; HRMS (FAB-MS): m/z calcd for C14H14O: 198.1045; found: 198.1046.