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Synlett 2013; 24(10): 1221-1224
DOI: 10.1055/s-0033-1338955
DOI: 10.1055/s-0033-1338955
cluster
N-Heterocyclic Carbene (NHC) Catalyzed Synthesis of α,α-Difluoro Esters
Further Information
Publication History
Received: 02 May 2013
Accepted after revision: 09 May 2013
Publication Date:
28 May 2013 (online)
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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
- for this article is available online at http://www.thieme-connect.com/ejournals/toc/synlett.
- Supporting Information
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References and Notes
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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.
For a review, see:
For selected recent examples, see:
For reviews on NHC redox catalysis, see:
For other recent reviews on NHC catalysis, see:
For NHC-catalyzed syntheses of α-fluoro acids and their derivatives, see: