Iron-Catalyzed Oxidative Coupling Reaction of N-Acyl Glycine Esters and Malonates

Abstract

An iron-catalyzed direct C–C double-bond formation process is described in this paper. Using DTBP as the oxidant and FeCl₃·6H₂O (20 mol%) as the catalyst, N-2-pyridinecarbonyl glycine esters were coupled with malonates to provide amido acrylates in moderate to good yields. A possible reaction pathway for the formation of the products is also discussed in this paper.

Key words

iron catalysis - glycine esters - malonates - DTBP - oxidative coupling

• References and Notes

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• 10 Typical Experimental Procedure the Synthesis of 3a To a mixture of 2a (0.2 mmol), FeCl₃·6H₂O (0.04 mmol), Cs₂CO₃ (0.10 mmol) in DCE (1.5 mL) were added malonic acid diethyl ester (0.40 mmol) and DTBP (0.40 mmol). The reaction vessel was capped and allowed to stir at 90 °C overnight. The volatiles were removed under reduced pressure, and the crude product was purified by flash chromatography on silica gel with (PE–EtOAc, 8:1) to give the product 3a (54 mg, 74%) as a yellow liquid. ¹H NMR (400 MHz, CDCl₃): δ = 12.77 (s, 1 H), 8.74 (s, 1 H), 8.19 (d, J = 7.8 Hz, 1 H), 7.91 (td, J = 7.7, 1.5 Hz, 1 H), 7.54 (ddd, J = 7.5, 4.8, 0.8 Hz, 1 H), 4.43 (q, J = 7.2 Hz, 2 H), 4.37 (q, J = 7.1 Hz, 2 H), 4.28 (q, J = 7.1 Hz, 2 H), 1.40 (d, J = 7.2 Hz, 3 H), 1.35 (d, J = 6.7 Hz, 3 H), 1.32 (d, J = 7.1 Hz, 3 H). ¹³C NMR (101 MHz, CDCl₃): δ = 165.70, 164.20, 162.72, 162.28, 148.89, 147.87, 145.07, 137.53, 127.40, 123.35, 107.15, 62.49, 61.68, 14.01, 13.71. ESI-HRMS: m/z calcd for C₁₇H₂₀N₂NaO₇: 387.1170; found: 387.1168 [M + Na]⁺.