Synlett 2012; 23(16): 2413-2415
DOI: 10.1055/s-0032-1317157
letter
© Georg Thieme Verlag Stuttgart · New York

Synthesis of β-Fluoro Amides Using Partially Hydrated Nickel Difluoride as Fluorine Source

Wan Xuan Zhang*
Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Hubei University, Wuhan 430062, P. R. of China   Fax: +86(27)88663043   Email: zhangwx@hubu.edu.cn
,
Li Su
Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Hubei University, Wuhan 430062, P. R. of China   Fax: +86(27)88663043   Email: zhangwx@hubu.edu.cn
,
Wei Gang Hu
Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Hubei University, Wuhan 430062, P. R. of China   Fax: +86(27)88663043   Email: zhangwx@hubu.edu.cn
,
Jie Zhou
Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Hubei University, Wuhan 430062, P. R. of China   Fax: +86(27)88663043   Email: zhangwx@hubu.edu.cn
› Author Affiliations
Further Information

Publication History

Received: 14 June 2012

Accepted after revision: 30 July 2012

Publication Date:
10 September 2012 (online)


Abstract

β-Fluoro amides were obtained from the reactions of ­activated aziridines with partially hydrated nickel difluoride (NiF2·nH2O, n <4) in good yields (47–82%) in the presence of tetra-n-butylammonium fluoride (20 mol%), while the non-activated aziridines did not react under the same conditions.

 
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  • 8 Complete dehydration of NiF2·4H2O needs vigorous condition: heating it to 500 °C under an atmosphere of HF.
  • 9 Typical Procedure for the Ring Opening of Aziridine with Partially Hydrated Nickel Difluoride: To a stirred solution of aziridine 1a (0.5 mmol) and partially hydrated nickel difluoride (NiF2·nH2O, n <4, 1.68 g, approx. 1 mmol) in i-PrOH (3.0 mL) was added Bu4NF (0.1 mmol), and the mixture was stirred at 90 °C until 1a was consumed (monitored by TLC). The mixture was filtered by short silica gel column and washed with CH2Cl2, then the solvent was removed in vacuum and the residue was purified by flash column chromatography on silica gel to yield 2a as a white amorphous solid. N-(2-Fluorocyclohexyl)-4-methylbenzenesulfonamide (2a): 82% yield; mp 95–96 °C (lit.5 95–97 °C). 1H NMR (600 MHz, CDCl3, 25 °C, TMS): δ = 1.22–1.26 (m, 4 H), 1.57–1.70 (m, 2 H), 2.01–2.13 (m, 2 H), 2.43 (s, 3 H), 3.17 (m, 1 H), 4.15, 4.25 (double multiplet, 2 J HF = 50.1 Hz, 1 H), 4.81 (d, J = 5.4 Hz, 1 H), 7.30 (d, J = 7.8 Hz, 2 H), 7.76 (d, J = 8.4 Hz, 2 H). 19F NMR (600 MHz, CDCl3, 25 °C, CF3COOH): δ = –179.3. IR (KBr): 3302, 2951, 1598, 1327, 1163, 1091, 1045, 893, 816, 667, 572, 551 cm–1.