Tin-free Radical Cyanation of Alkyl Iodides and Alkyl Phenyl Tellurides

Abstract

As a result of much faster phenyl telluride group transfer relative to the corresponding iodine atom transfer, tin-free radical cyanation of alkyl phenyl tellurides has been achieved with p-toluenesufonyl cyanide and methyl allyl sulfone in the presence of V-40 as initiator.

Key words

radicals - tin-free - cyanation - alkyl phenyl tellurides - sulfones

References

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9

Typical procedure for Equation [2] : The degassed solution of ethyl 4-iodobutyrate (4, 48 mg, 0.20 mmol), p-toluene-sulfonyl cyanide (2, 46 mg, 0.24 mmol) and hexamethylditin (79 mg, 0.24 mmol) in benzene (1 mL) was irradiated under 300 nm UV lamp at room temperature for 2 h. The solvent was evaporated under reduced pressure and the residue was chromatographed on a silica gel column (n-hexane/ethyl acetate = 1:5) to yield ethyl 4-cyanobutyrate (5, 25 mg, 0.18 mmol, 88% yield). ¹H NMR (CDCl₃, 300 MHz) δ 1.21 (t,
J = 7.1 Hz, 3 H), 1.87-1.97 (m, 2 H), 2.38-2.44 (m, 4 H), 4.09 (q, J = 7.1 Hz, 2 H); ¹³C NMR (CDCl₃, 100 MHz) δ 14.0, 16.4, 20.6, 32.3, 60.6, 118.9, 171.8; IR (NaCl) 2994, 2950, 2880, 2365, 2344, 2252, 1734, 1458, 1378, 1222, 1198, 1028 cm^-1.

13

Typical procedure for Equation [6] : The degassed solution of 4-phenoxybutyl phenyl telluride (13, 65 mg, 0.18 mmol), p-toluenesulfonyl cyanide (2, 70 mg, 0.37 mmol), methyl allyl sulfone (6, 44 mg, 0.37 mmol) and V-40 (9 mg, 0.037 mmol) in t-butylbenzene (1 mL) was stirred at 140 °C under N₂ for 12 h. The solvent was evaporated under reduced pressure and the residue was chromatographed on a silica gel column (n-hexane/ethyl acetate = 1:10) to yield 5-phenoxy pentanenitrile (29 mg, 0.16 mmol, 89% yield). ¹H NMR (CDCl₃, 300 MHz) 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 (CDCl₃, 100 MHz) δ 16.6, 22.0, 27.8, 66.0, 113.9, 119.0, 120.4, 129.0, 158.2; IR (NaCl) 2946, 2877, 2362, 2343, 2247, 1600, 1498, 1245 cm^-1.