Correction to: Regioselective synthesis of pyridines by redox alkylation of pyridine N-oxides with malonates

Correction to: Monatsh Chem https://doi.org/10.1007/s00706-017-2081-y

The original version of this article unfortunately contained mistakes. In section “General procedure” some numbers were missing. The corrected text is given below.

General procedure

All flasks and stirrer bars were flame dried before use. To the N-oxide (0.2 mmol, 1.0 equiv.), dissolved in 2 cm³ dichloromethane was added Tf₂O (0.3 mmol, 1.5 equiv.) at 0 °C. In another flask, a suspension of NaH (0.7 mmol, 3.5 equiv.) in 1 cm³ tetrahydrofuran was cooled to 0 °C and the malonate (0.7 mmol, 3.5 equiv.) was added. After 15 min, the malonate solution was added to the activated N-oxide solution and the mixture was stirred at room temperature for 1 h. The reaction was quenched with NH₄Cl solution and the aqueous phase was extracted with dichloromethane. The combined organic layers were washed with brine before being dried over MgSO₄. The solvents were removed under reduced pressure and the crude product was purified by column chromatography.

Dibenzyl 2-(2,6-dimethylpyridin-4-yl)malonate (6a, C24H23NO4)

The product was prepared according to the general procedure. Purification by column chromatography (EtOAc:heptane = 1:1) yielded the product (41.0 mg, 53%) as a pale yellow solid. ¹H NMR (400 MHz, CDCl₃): δ = 7.28–7.20 (m, 10H), 6.88 (s, 2H), 5.11 (dd, J = 12.0, 18.1 Hz, 4H), 4.56 (s, 1H), 2.43 (s, 6H) ppm; ¹³C NMR (101 MHz, CDCl₃): δ = 167.0, 158.4, 141.5, 135.1, 128.7, 128.7, 128.4, 120.9, 67.9, 57.3, 24.6 ppm; IR: $\bar{\nu }$ = 3064, 3033, 2955, 2922, 1732, 1605, 1569, 1497, 1453, 1375, 1297, 1140 cm⁻¹; HRMS (ESI): m/z calculated for [M + H]⁺ 390.1700, found 390.1701.

Diethyl 2-(2,6-dimethylpyridin-4-yl)-2-fluoromalonate (6b, C₁₄H₁₈FNO₄)

The product was prepared according to the general procedure. Purification by column chromatography (EtOAc:heptane = 1:3) yielded the product (34.3 mg, 61%) as a pale yellow liquid. ¹H NMR (400 MHz, CDCl₃): δ = 7.19 (s, 2H), 4.33 (q, J = 7.1, 4H), 2.56 (s, 6H), 1.32 (t, J = 7.1 Hz, 6H) ppm; ¹³C NMR (101 MHz, CDCl₃): δ = 164.9 (d, J = 25.0 Hz), 158.3, 142.4 (d, J = 22.4 Hz), 116.8 (d, J = 9.0 Hz), 93.2 (d, J = 202.9 Hz), 63.4, 24.8, 14.0 ppm; ¹⁹F NMR (659 MHz, CDCl₃): − 165.2 ppm; IR: $\bar{\nu }$ = 2983, 2927, 1753, 1604, 1569, 1445, 1412, 1369, 1270, 1230, 1174, 1105, 1044, 1010 cm⁻¹; HRMS (ESI): m/z calculated for [M + H]⁺ 284.1293, found 284.1292.

Diethyl 2-(2-cyanoethyl)-2-(2,6-dimethylpyridin-4-yl)malonate (6c, C₁₇H₂₂N₂O₄)

The product was prepared according to the general procedure. Purification by column chromatography (EtOAc:heptane = 1:1) yielded the product (48.4 mg, 76%) as a pink liquid. ¹H NMR (400 MHz, CDCl₃): δ = 6.90 (s, 2H), 4.32–4.24 (m, 4H), 2.61–2.57 (m, 2H), 2.54 (s, 6H), 2.37–2.33 (m, 2H), 1.28 (t, J = 7.1 Hz, 6H) ppm; ¹³C NMR (125 MHz, CDCl₃): δ = 168.8, 158.6, 145.0, 119.0, 118.9, 62.6, 61.3, 32.0, 24.8, 14.0, 13.5 ppm; IR: $\bar{\nu }$ = 2982, 2937, 2249, 1728, 1603, 1564, 1445, 1368, 1254, 1188, 1079, 1016 cm⁻¹; HRMS (ESI): m/z calculated for [M + H]⁺ 319.1652, found 319.1651.

Diethyl 2-(2,6-dimethylpyridin-4-yl)-2-methylmalonate (6d, C₁₅H₂₁NO₄)

The product was prepared according to the general procedure. Purification by column chromatography (EtOAc:heptane = 1:1) yielded the product (33.6 mg, 60%) as a pale yellow liquid. ¹H NMR (400 MHz, CDCl₃): δ = 6.94 (s, 2H), 4.25 (m, 4H), 2.52 (s, 6H), 1.81 (s, 3H), 1.26 (t, J = 7.2 Hz, 6H) ppm; ¹³C NMR (101 MHz, CDCl₃): δ = 170.7, 157.9, 147.8, 119.1, 62.1, 58.6, 24.8, 22.2, 14.1 ppm; IR: $\bar{\nu }$ = 2982, 1728, 1604, 1564, 1447, 1414, 1377, 1253, 1181, 1105, 1017 cm⁻¹; HRMS (ESI): m/z calculated for [M + H]⁺ 280.1543, found 280.1543.

Diethyl 2-allyl-2-(2,6-dimethylpyridin-4-yl)malonate (7a, C₁₇H₂₃NO₄)

The product was prepared according to the general procedure. Purification by column chromatography (EtOAc:heptane = 1:3) yielded the product (43.6 mg, 71%) as a pale yellow liquid. ¹H NMR (400 MHz, CDCl₃): δ = 7.01 (s, 2H), 5.75–5.64 (m, 1H), 5.08 (m, 1H), 5.04(s, 1H), 4.29–4.16 (m, 4H), 3.00 (d, J = 7.1 Hz, 2H), 2.52 (s, 6H), 1.25 (t, J = 7.1, 6H) ppm; ¹³C NMR (101 MHz, CDCl₃): δ = 169.5, 157.8, 146.3, 132.5, 119.7, 119.4, 62.4, 62.0, 40.3, 24.8, 14.1 ppm; IR: $\bar{\nu }$ = 2981, 2926, 1729, 1602, 1563, 1443, 1414, 1367, 1295, 1270, 1230, 1196, 1162 cm⁻¹; HRMS (ESI): m/z calculated for [M + H]⁺ 306.1700, found 306.1703.

Diethyl 2-allyl-2-(4-methylpyridin-2-yl)malonate (7b, C₁₆H₂₁NO₄)

The product was prepared according to the general procedure. Purification by column chromatography (EtOAc:heptane = 1:10) yielded the product (48.8 mg, 84%) as a pale yellow liquid. ¹H NMR (400 MHz, CDCl₃): δ = 8.39 (dd, J = 0.5, 5.0 Hz, 1H), 7.56 (app t, J = 0.7 Hz, 1H), 7.01–6.99 (m, 1H), 5.82–5.75 (m, 1H), 5.04–4.99 (m, 2H), 4.27–4.20 (m, 4H), 3.12 (d, J = 7.2 Hz, 2H), 2.36 (s, 3H), 1.24 (t, J = 7.1 Hz, 6H) ppm; ¹³C NMR (101 MHz, CDCl₃): δ = 169.9, 156.6, 148.6, 147.1, 133.6, 124.8, 123.5, 118.6, 65.3, 61.7, 40.4, 21.4, 14.1 ppm; IR: $\bar{\nu }$ = 2980, 2936, 1729, 1601, 1444, 1298, 1195 cm⁻¹; HRMS (ESI): m/z calculated for [M + H]⁺ 292.1543, found 292.1543.

Diethyl 2-allyl-2-(4-phenylpyridin-2-yl)malonate (7c, C₂₁H₂₃NO₄)

The product was prepared according to the general procedure. Purification by column chromatography (EtOAc:heptane = 1:10) yielded the product (48.0 mg, 68%) as a pale yellow liquid. ¹H NMR (400 MHz, CDCl₃): δ = 8.59 (dd, J = 0.7, 5.1 Hz, 1H), 7.88 (dd, J = 0.7, 1.7 Hz, 1H), 7.65–7.63 (m, 2H), 7.48–7.41 (m, 4H), 5.86–5.79 (m, 1H), 5.06–5.02 (m, 2H), 4.30–4.24 (m, 4H), 3.17 (d, J = 7.1 Hz, 2H), 1.26 (t, J = 7.1 Hz, 6H) ppm; ¹³C NMR (125 MHz, CDCl₃): δ = 169.8, 157.2, 149.2, 148.5, 138.6, 133.3, 129.2, 129.1, 127.3, 122.4, 120.7, 119.0, 65.5, 61.8, 40.5, 14.2 ppm; IR: $\bar{\nu }$ = 3062, 2980, 2935, 1729, 1594, 1547, 1467, 1225, 1036 cm⁻¹; HRMS (ESI): m/z calculated for [M + H]⁺ 354.1700, found 354.1699.

Diethyl 2-allyl-2-(4-cyanopyridin-2-yl)malonate (7d, C₁₆H₁₈N₂O₄)

The product was prepared according to the general procedure. Purification by column chromatography (EtOAc:heptane = 1:10) yielded the product (10.3 mg, 17%) as a pale yellow liquid. ¹H NMR (400 MHz, CDCl₃): δ = 8.72 (dd, J = 0.9, 5.0 Hz, 1H), 7.98 (app t, J = 1.3 Hz, 1H), 7.43 (dd, J = 1.3, 5.0 Hz, 1H), 5.74–5.63 (m, 1H), 5.04–5.01 (m, 2H), 4.29–4.22 (m, 4H), 3.12 (d, J = 7.3 Hz, 2H), 1.25 (t, J = 7.1 Hz, 6H) ppm; ¹³C NMR (101 MHz, CDCl₃): δ = 169.0, 158.5, 149.6, 132.4, 126.5, 124.0, 120.5, 119.7, 116.8, 65.3, 62.2, 40.3, 14.1 ppm; IR: $\bar{\nu }$ = 3077, 2981, 2933, 2239, 1730, 1594, 1467, 1299, 1168, 1044 cm⁻¹; HRMS (ESI): m/z calculated for [M + Na]⁺ 325.1159, found 325.1157.

The original article has been corrected.