Radical Cyanation of Alkyl Iodides with Diethylphosphoryl Cyanide

Abstract

The β-elimination of an organophosphoryl group from an iminyl radical is observed for the first time. On the basis of this finding, radical cyanation of alkyl iodides is achieved by using diethylphosphoryl cyanide.

Key words

radical - cyanide - elimination - alkyl halides

References and Notes

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17

Typical Procedure for Radical Cyanation
Photochemical Conditions A
A dry benzene solution (2 mL) of 4-phenoxybutyl iodide (2, 55 mg, 0.2 mmol), diethylphosphoryl cyanide (3, 90 µL, 0.6 mmol), and hexamethylditin (79 mg, 0.24 mmol) in a quartz tube was degassed with nitrogen for 10 min and then irradiated at 300 nm in Rayonet photochemical reactor for 12 h. The solvent was evaporated under reduced pressure, and the residue was separated by a silica gel column chromatography using EtOAc and n-hexane (1:5) as eluant to give 4-phenoxybutyl cyanide (28 mg, 80%).^¹¹d MW (C₁₁H₁₃NO): 175.23. ^¹H NMR (400 MHz, CDCl₃): δ = 1.85-1.95 (m, 4 H), 2.41-2.45 (t, J = 6.7 Hz, 2 H), 3.98-4.00 (t, J = 5.7 Hz, 2 H), 6.85-6.92 (d, J = 5.6 Hz, 2 H), 6.93-6.95 (t, J = 7.3 Hz, 1 H), 7.23-7.28 (m, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 16.6, 22.0, 27.8, 66.0, 113.9, 119.0, 120.4, 129.0, 158.2. IR (polymer): 2927, 1601, 1586, 1497, 1474, 1247, 757, 693 cm^-¹. HRMS: m/z calcd for C₁₁H₁₃NO [M⁺]: 175.0997; found: 175.0998.
Thermal Conditions B
A solution of 2 (110 mg, 0.4 mmol), 3 (180 µL, 1.2 mmol), and DLP (31 mg, 0.08 mmol) in chlorobenzene (4 mL) was degassed with nitrogen for 10 min, and then the solution was heated at 110 ˚C under nitrogen for 24 h. The solvent was evaporated under reduced pressure, and the residue was separated by a silica gel column chromatography using EtOAc and n-hexane (1:5) as eluant to give 4-phenoxybutyl cyanide (35 mg, 50%) with recovery of 2 (22 mg, 20%).