Synlett 2008(2): 221-224  
DOI: 10.1055/s-2007-1000878
LETTER
© Georg Thieme Verlag Stuttgart · New York

Highly Efficient Copper-Catalyzed O-Arylation Using Readily Available (S)-N-Methylpyrrolidine-2-Carboxamide as the Ligand

Xianghao Liua, Hua Fu*a, Yuyang Jianga,b, Yufen Zhaoa
a Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, P. R. of China
e-Mail: fuhua@mail.tsinghua.edu.cn;
b Key Laboratory of Chemical Biology, Guangdong Province, College of Shenzhen, Tsinghua University, Shenzhen 518057, P. R. of China
Fax: +86(10)62781695;
Further Information

Publication History

Received 14 September 2007
Publication Date:
21 December 2007 (online)

Abstract

A highly efficient and readily available catalyst system for O-arylation of various phenols using CuI and (S)-N-methylpyrrolidine-2-carboxamide (Pro-NHMe) was developed. The reaction is widely applicable to the synthesis of diaryl ethers

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General Procedure for the Preparation of Compounds 3a-m: Aryl halide (2 mmol for entries 1-8 and 10-14, 1 mmol for entry 9 in Table [1] ), substituted phenol (3 mmol) and (S)-N-methylpyrrolidine-2-carboxamide hydrochloride (66 mg, 0.4 mmol) were added to a flask with potassium phosphate (607 mg, 4.4 mmol) and DMF containing 3% H2O (3 mL), and the mixture was stirred for 30 min at r.t. Under a nitrogen atmosphere CuI (40 mg, 0.2 mmol) was added to the flask. The flask was immersed in an oil bath, and the reaction mixture was stirred at 110 °C for the reaction time shown in Table [1] . The reaction mixture was then allowed to cool to r.t., diluted with EtOAc (10 mL) and filtered, and the filtrate was concentrated under vacuum to give the crude product. Purification by column chromatography on silica gel (hexane-EtOAc, 15:1 → 50:1) afforded the desired pure product.
1-Methoxy-4- o -tolyloxybenzene (3d):17 colorless oil. 1H NMR (300 MHz, CDCl3): δ = 7.18 (m, 1 H), 7.07 (m, 1 H), 6.97 (m, 1 H), 6.79 (m, 5 H), 3.73 (s, 3 H), 2.26 (s, 3 H). 13C NMR (75 MHz, CDCl3): δ = 156.03, 155.51, 151.26, 131.49, 129.21, 127.18, 123.28, 119.53, 118.18, 114.98, 55.76, 16.42. HRMS (EI): m/z [M+] calcd for C14H14O2: 214.0994; found: 214.0986.
1-Bromo-4-(4-methoxyphenoxy)benzene (3g): white solid; mp 84-86 °C. 1H NMR (300 MHz, CDCl3): δ = 7.36 (d, J = 8.25 Hz, 2 H), 6.86-6.97 (dd, J = 8.94, 25.08 Hz, 4 H), 6.80 (d, J = 8.91 Hz, 2 H), 3.79 (s, 3 H). 13C NMR (75 MHz, CDCl3): δ = 157.9, 156.3, 149.7, 132.6, 121.0, 119.3, 115.1, 114.8, 55.7. HRMS (EI): m/z [M+] calcd for C13H11BrO2: 277.9942; found: 277.9948.