Radical Alkylations of Alkyl
Halides and Unactivated C-H Bonds Using Vinyl Triflates

Jin Young Lee; Kyoung-Chan Lim; Xiangjian Meng; Sunggak Kim

doi:10.1055/s-0029-1219960

LETTER

Radical Alkylations of Alkyl Halides and Unactivated C-H Bonds Using Vinyl Triflates

Jin Young Lee^a, Kyoung-Chan Lim^a, Xiangjian Meng^b, Sunggak Kim*^a,b
^a Department of Chemistry, Korea Advanced Institute of Science & Technology, Daejeon 305-701, Korea
^b Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
Fax: +65(6791)1961; e-Mail: sgkim@ntu.edu.sg;

Abstract

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Abstract

Radical alkylations of activated alkyl iodides and bromides were achieved using vinyl triflates in the presence of hexadimethyltin, whereas those of unactivated C-H bonds using vinyl triflates proceeded cleanly under tin-free conditions.

Key words

alkylation - radical reaction - ketone - vinyl triflate

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References

References and Notes

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Typical procedure for radical alkylation of a carbonyl compound: A solution of iodomethyl phenylsulfone (56 mg, 0.2 mmol), vinyl triflate 7 (76 mg, 0.3 mmol), and hexamethylditin (33 mg, 0.1 mmol) in benzene (1 mL; 0.2 M in iodide) was degassed with nitrogen for 10 min, and the solution was then irradiated in a photochemical reactor (300 nm) for 5 h. The solvent was evaporated under reduced pressure and the residue was purified by silica gel column chromatography (EtOAc-hexane, 1:10) to give 1-phenyl-3-(phenylsulfonyl)propan-1-one (38 mg, 69%) as a colorless oil. ^¹H NMR (CDCl₃, 400 MHz): δ = 3.45-3.49 (m, 2 H), 3.52-3.56 (m, 2 H), 7.42-7.46 (m, 2 H), 7.55-7.57 (m, 3 H), 7.63-7.64 (m, 1 H), 7.88-7.94 (m, 4 H); ^¹³C NMR (CDCl₃, 100 MHz): δ = 31.3, 51.0, 127.9 (C2), 128.0 (C2), 128.7 (C2), 129.4 (C2), 133.7, 133.9, 135.8, 139.0, 195.3

Typical procedure for radical alkylation of an unactivated C-H bond: A solution of vinyl triflate 9 (76 mg, 0.3 mmol) and AIBN (5 mg, 0.03 mmol) in THF (1 mL) was degassed with nitrogen for 10 min, and the solution was heated at reflux (80 ˚C) for 9 h under nitrogen. The solvent was evaporated under reduced pressure and the residue was purified by silica gel column chromatography (EtOAc-hexane, 1:50) to give 16 (41 mg, 65%) as a colorless oil. ^¹H NMR (CDCl₃, 400 MHz): δ = 1.33 (t, J = 7.2 Hz, 3 H), 1.48-1.55 (m, 1 H), 1.84-1.92 (m, 2 H), 2.06-2.14 (m, 1 H), 2.94 (dd, J = 16.5, 5.7 Hz, 1 H), 3.10 (dd, J = 16.5, 7.1 Hz, 1 H), 3.67-3.73 (m, 1 H), 3.80-3.85 (m, 1 H), 4.29 (q, J = 7.2 Hz, 2 H), 4.26-4.32 (m, 1 H); ^¹³C NMR (CDCl₃, 100 MHz): δ = 13.9, 25.4, 31.4, 45.1, 62.4, 67.9, 74.3, 160.8, 192.6