Cyanation of Aryl Chlorides with Potassium Hexacyanoferrate(II) Catalyzed by Cyclopalladated Ferrocenylimine Tricyclohexylphosphine Complexes

Abstract

Cyanation of aryl chlorides with potassium hexacyano­ferrate(II) catalyzed by cyclopalladated ferrocenylimine tricyclohexylphosphine complex has been described. This method is applicable to both activated and deactivated aryl chlorides. The ­corresponding aryl nitriles were isolated in good to excellent yields

Key words

cyclopalladium - cyanation - aryl chloride - catalysis - coupling

References and Notes

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19

General Procedure.
A reaction vessel was charged with 1 mmol Na₂CO₃, 0.22 mmol K₄[Fe(CN)₆]·3H₂O and 2% mol catalyst 2a. The vessel was then evacuated and backfilled with N₂ four times. Then, 1 mmol aryl chloride in 1 mL NMP was added to the vessel. The mixture was heated at 140 °C for 16-24 h. The suspension was cooled down to r.t., diluted with 5 mL CH₂Cl₂ and washed with 5 mL H₂O. The aqueous layer was extracted twice with CH₂Cl₂ (3 mL) and the combined organic layers were dried over MgSO₄. After evaporation of the solvents the residue was subjected to TLC (hexane-EtOAc). All prepared compounds were known and identified by ¹H NMR, ¹³C NMR and MS.
Selected Data.
Compound 4c: ¹H NMR (400 MHz, CDCl₃): δ = 2.53 (s, 6 H), 7.11 (d, J = 7.7 Hz, 2 H), 7.34 (dd, J = 7.7 Hz, 1 H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 20.8, 113.3, 117.3, 127.3, 132.1, 142.1 ppm. MS (ESI): m/z = 154.1 [M + Na]⁺.
Compound 4e: ¹H NMR (400 MHz, CDCl₃): δ = 3.87 (s, 3 H), 6.95 (d, J = 8.9 Hz, 2 H), 7.58 (d, J = 8.9 Hz, 2 H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 55.3, 103.7, 114.5, 119.0, 133.7, 162.6 ppm. MS (ESI): m/z = 156.0 [M + Na]⁺.
Compound 4i: ¹H NMR (400 MHz, CDCl₃): δ = 1.42 (t, J = 7.2 Hz, 3 H), 4.42 (q, J = 7.1 Hz, 2 H), 7.74 (d, J = 8.3 Hz, 2 H), 8.14 (d, J = 8.3 Hz, 2 H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 14.0, 61.6, 116.0, 117.8, 129.8, 131.9, 134.1, 164.7 ppm. MS (ESI): m/z = 197.8 [M + Na]⁺.
Compound 4j: ¹H NMR (400 MHz, CDCl₃): δ = 7.45 (m, 1 H), 7.98 (m, 1 H), 8.83 (m, 1 H), 8.91 (s, 1 H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 110.3, 116.5, 123.6, 139.3, 152.5, 153.0 ppm. MS (ESI): m/z = 105.0 [M + H]⁺.