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Synlett 2013; 24(11): 1443-1447
DOI: 10.1055/s-0033-1338939
letter
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Aryl Thiocyanates via Copper-Catalyzed Aerobic Oxidative Cross-Coupling between Arylboronic Acids and KSCN

Nan Sun
a   College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, P. R. of China   Fax: +86(571)88320103   Email: xinquan@zjut.edu.cn
,
Han Zhang
a   College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, P. R. of China   Fax: +86(571)88320103   Email: xinquan@zjut.edu.cn
,
Weimin Mo
a   College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, P. R. of China   Fax: +86(571)88320103   Email: xinquan@zjut.edu.cn
,
Baoxiang Hu
a   College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, P. R. of China   Fax: +86(571)88320103   Email: xinquan@zjut.edu.cn
,
Zhenlu Shen
a   College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, P. R. of China   Fax: +86(571)88320103   Email: xinquan@zjut.edu.cn
,
Xinquan Hu*
a   College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou 310014, P. R. of China   Fax: +86(571)88320103   Email: xinquan@zjut.edu.cn
b   State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, P. R. of China
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Further Information

Publication History

Received: 16 March 2013

Accepted after revision: 17 April 2013

Publication Date:
15 May 2013 (online)

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Abstract

A new protocol for the preparation of aryl thiocyanates by the cross-coupling reaction of arylboronic acids with KSCN salt is described. The coupling reaction was catalyzed by 20 mol% of copper acetate in the presence of 2.0 equivalents 4-methylpyridine serving both as ligand and base under 0.2 MPa of molecular oxygen. A variety of arylboronic acids, including those with substituents at ortho position, were suitable under the reaction conditions.

Key words

aryl thiocyanates - arylboronic acids - potassium thio­cyanate - copper acetate - oxidative cross-coupling reaction

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  • References and Notes

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  • 18 General Procedure for the Preparation of Aryl Thiocyanates To a Teflon-lined stainless steel autoclave (250 mL) was added aryl boronic acid (10 mmol), KSCN (1.07 g, 11 mmol), Cu(OAc)2 (0.36 g, 2 mmol), 3 Å MS (2.5 g), and MeCN (25 mL). The autoclave was closed and charged with oxygen to 0.2 MPa. The autoclave was then set into the preheated (80 °C) oil bath. After the reaction proceeded within 12 h, the autoclave was cooled to r.t. and carefully depressurized. The mixture in the autoclave was filtered to remove the catalyst and 3 Å MS and washed with MeCN. The combined filtrate was concentrated under reduced pressure. The residual was purified by flash chromatography through a silica column using PE–EtOAc as the eluent under the protection of N2 to afford the desired products. The products were characterized by IR, 1H NMR, 13C NMR, and HRMS. Phenyl Thiocyanate (2a) Yellowish oil. IR (neat): ν = 2173 cm–1. 1H NMR (500 MHz, CDCl3): δ = 7.43–7.56 (m, 5 H). 13C NMR (125 MHz, CDCl3): δ = 110.5, 124.4, 129.5, 130.06, 130.23. HRMS (EI): m/z calcd for C7H5NS [M]+: 135.0143; found: 135.0140. CAS Reg. No. 5285-87-0. 2-Methoxyphenyl Thiocyanate (2c) Yellow oil. IR (neat): ν = 2153 cm–1. 1H NMR (500 MHz, CDCl3): δ = 3.94 (s, 3 H), 6.94–7.59 (m, 4 H). 13C NMR (125 MHz, CDCl3): δ = 56.2, 110.5, 111.4, 113.1, 122.1, 129.9, 130.5, 156.5. HRMS (EI): m/z calcd for C8H7NOS [M]+: 165.0248; found: 165.0252. CAS Reg. No. 14372-66-8. 4-Fluorophenyl Thiocyanate (2i) Colorless oil. IR (neat): ν = 2153 cm–1. 1H NMR (500 MHz, CDCl3): δ = 7.15–7.59 (m, 4 H). 13C NMR (125 MHz, CDCl3): δ = 110.6, 117.6 (d, J = 22.7 Hz), 119.2 (d, J = 3.3 Hz), 133.2 (d, J = 8.9 Hz), 163.6 (d, J = 250.1 Hz). HRMS (EI): m/z calcd for C7H4NSF [M]+: 153.0048; found: 153.0048. CAS Reg. No. 2924-02-9. 2-Bromophenyl Thiocyanate (2k) Pink oil. IR (neat): ν = 2161 cm–1. 1H NMR (500 MHz, CDCl3): δ = 7.25–7.74 (m, 4 H). 13C NMR (125 MHz, CDCl3): δ = 109.6, 121.8, 127.1, 129.07, 129.44, 130.1, 133.6. HRMS (EI): m/z calcd for C7H4NSBr [M]+: 212.9248; found: 212.9238. CAS Reg. No. 55757-32-9. 4-(Methoxycarbonyl)phenyl Thiocyanate (2n) White soild; mp 62.7 °C. IR (KBr): ν = 2153, 1708 cm–1. 1H NMR (500 MHz, CDCl3): δ = 3.96 (s, 3 H), 7.57–8.12 (m, 4 H). 13C NMR (125 MHz, CDCl3): δ = 52.6, 109.1, 128.5, 130.47, 130.93, 131.21, 165.8. HRMS (EI): m/z calcd for C9H7NO2S [M]+: 193.0198; found: 193.0203. CAS Reg. No. 1879-22-7.