Synlett 2013; 24(10): 1221-1224
DOI: 10.1055/s-0033-1338955
cluster
© Georg Thieme Verlag Stuttgart · New York

N-Heterocyclic Carbene (NHC) Catalyzed Synthesis of α,α-Difluoro Esters

Xiuqin Dong
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, P. R. of China   Fax: +852(2358)1549   Email: sunjw@ust.hk
,
Yu-Ming Zhao
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, P. R. of China   Fax: +852(2358)1549   Email: sunjw@ust.hk
,
Jianwei Sun*
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, P. R. of China   Fax: +852(2358)1549   Email: sunjw@ust.hk
› Author Affiliations
Further Information

Publication History

Received: 02 May 2013

Accepted after revision: 09 May 2013

Publication Date:
28 May 2013 (online)

Abstract

A process for the synthesis of α,α-difluoro esters by NHC-catalyzed fluorination is described. The internal redox process exhibits good efficiency, selectivity, and functional-group compatibility. It provides an alternative strategy for the formation of the useful gem-difluoromethylene unit in organic molecules.

Supporting Information

 
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  • 9 Typical Procedure In a glove box, an oven-dried 4 mL vial was charged with triazolium salt A (10.9 mg, 0.04 mmol), anhyd CHCl3 (2 mL), K3PO4 (169.8 mg, 0.8 mmol), and enal 1a (0.2 mmol). Selectfluor (248 mg, 0.7 mmol) was then added, and the vial was capped and removed from the glove box. The reaction mixture was stirred at 50 °C for 17 h. The solvent was removed in vacuo, and the product 2a was purified by silica gel chromatography (10% EtOAc in hexanes) as colorless oil (68%). 1H NMR (400 MHz, CDCl3): δ = 7.44–7.40 (m, 2 H), 7.39–7.35 (m, 3 H), 7.11–7.06 (dt, J 1 = 16.0 Hz, J 2 = 2.4 Hz, 1 H), 6.35–6.26 (dt, J 1 = 16.4 Hz, J 2 = 11.6 Hz, 1 H), 3.91 (s, 3 H). 13C NMR (100 MHz, CDCl3): δ = 164.4 (t, J = 35.0 Hz), 136.9 (t, J = 9.0 Hz), 134.0, 129.7, 128.8, 127.4, 118.7 (t, J = 25.0 Hz), 112.8 (t, J = 244.0 Hz), 53.5.