Solvent-Free Anti-Markovnikov Addition of Thiols to Alkenes Using Anhydrous Cerium(III) Chloride as Catalyst

Abstract

The anti-Markovnikov addition of thiols to alkenes using CeCl₃ as catalyst is described. The products were obtained in good to excellent yields. The reaction occurred under solvent-free conditions at room temperature.

Key words

anti-Markovnikov addition - cerium(III) chloride - solvent free reaction - green chemistry

References and Notes

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14

Typical procedure for the synthesis of diorganyl sulfides 3: To a mixture of alkene 1 (1.0 mmol) and CeCl₃ (0.0123 g, 0.05 mmol), was added thiol 2 (1.1 mmol). The reaction mixture was stirred at r.t. for the time indicated in Table  [²] (progress of the reaction was followed by GC). The resulting reaction mixture was extracted with EtOAc (3 × 10 mL) and the organic phase was washed with water, NaOH solution (2%) and then brine and dried over anhydrous MgSO₄. The solvent was removed under reduced pressure and the residue was purified by flash chromatography on silica gel (EtOAc-hexanes, 5:95). Spectral data of selected compounds: 3a:^{¹5 ¹}H NMR (200 MHz, CDCl₃): δ = 1.20-2.10 (m, 10 H), 3.05-3.13 (m, 1 H), 7.16-7.51 (m, 5 H); ^¹³C NMR (100 MHz, CDCl₃): δ = 25.67, 25.92, 33.24, 46.42, 126.42, 128.60, 131.73, 135.12. 3b:^{¹6 ¹}H NMR (200 MHz, CDCl₃): δ = 0.87 (t, J = 6.8 Hz, 3 H), 1.25-1.54 (m, 10 H), 1.63 (quint, J = 7.2 Hz, 2 H), 2.90 (t, J = 7.2 Hz, 2 H), 7.13-7.33 (m, 5 H); ^¹³C NMR (100 MHz, CDCl₃): δ = 14.06, 22.61, 28.81, 29.10 (2C), 29.13, 31.76, 33.50, 125.54, 128.74 (2C), 137.03. 3f:^{¹7 ¹}H NMR (200 MHz, CDCl₃): δ = 2.84 (t, J = 7.48 Hz, 2 H), 3.04 (t, J = 7.48 Hz, 2 H), 3.78 (s, 3 H), 6.87 (d, J = 8.5 Hz, 2 H), 7.13-7.38 (m, 7 H); ^¹³C NMR (100 MHz, CDCl₃): δ = 35.85, 37.16, 55.26, 114.55, 126.26, 128.38, 128.45, 133.18 (2C), 140.31, 158.89. 3i:^{¹8 ¹}H NMR (200 MHz, CDCl₃): δ = 1.61-2.07 (m, 6 H), 3.57 (m, 1 H), 4.14 (m, 1 H), 5.17 (m, 1 H), 7.21 (d, J = 8.62 Hz, 2 H), 7.37 (d, J = 8.62 Hz, H); ^¹³C NMR (100 MHz, CDCl₃): δ = 21.45, 25.36, 31.36, 64.36, 85.23, 128.81, 132.11, 132.71, 133.81.