Iodoarene-Mediated α-Tosyloxylation of Ketones with MCPBA and p-Toluenesulfonic Acid

Abstract

Alkyl aryl ketones and dialkyl ketones could be converted into the corresponding α-tosyloxy ketones by the reaction with MCPBA and p-toluenesulfonic acid monohydrate (PTSA˙H₂O) in the presence of a catalytic amount of molecular iodine (I₂) in a mixture of acetonitrile and 2,2,2-trifluoroethanol, although the yields were dependent on the ketones (method A). The same conversion of alkyl aryl ketones and dialkyl ketones into the corresponding α-­tosyloxy ketones could be smoothly carried out by the reaction with MCPBA and PTSA˙H₂O in the presence of catalytic amounts of ­iodine and tert-butylbenzene in a mixture of acetonitrile and 2,2,2-trifluoroethanol (method B). In those reactions, p-iodotoluene and 4-tert-butyl-1-iodobenzene were formed at first in method A and method B, respectively, and then they were converted into p-[(hydroxy)(tosyloxy)]iodotoluene and 4-tert-butyl-1-[(hydroxy)(tosyloxy)iodo]benzene by the reaction with MCPBA and PTSA˙H₂O. p-[(Hydroxy)(tosyloxy)]iodotoluene and 4-tert-butyl-1-[(hydroxy)-(tosyloxy)iodo]benzene worked as an α-tosyloxylation reagent of ketones.

Key words

molecular iodine - tert-butylbenzene - MCPBA - α-tosyl­oxy ketone - ketone - p-toluenesulfonic acid - catalyst

References and Notes

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7

Typical Procedure for Iodoarene-Mediated α-Tosyl-oxylation of Ketones with MCPBA and p -TsOH˙H ₂ O Method A I₂ (0.1 mmol), p-TsOH˙H₂O (2.1 mmol), and MCPBA (2.2 mmol) were dissolved in a mixture of MeCN (3 mL) and 2,2,2-trifluoroethanol (3 mL) under argon atmosphere. The resulting solution was stirred at r.t. until the color of I₂ faded completely (1-2 h). Then, a solution of acetophenone (1 mmol) in MeCN (2 mL) was added, and the mixture was stirred for 3 h at 60 ˚C under argon atmosphere. After the reaction, the reaction mixture was poured into a solution of sat. aq NaHCO₃ and Na₂SO₃, and the whole was extracted with CHCl₃ (3 × 20 mL). The organic layer was dried over Na₂SO₄. After removal of the solvent under reduced pressure, α-tosyloxyacetophenone was obtained in the crude state. Pure α-tosyloxyacetophenone was obtained in 71% yield (206 mg) by short flash column chromatography on silica gel (EtOAc-hexane = 1:3). Method B To a stirred solution of tert-butylbenzene (0.2 mmol) in a mixture of MeCN (3 mL) and 2,2,2-trifluoroethanol (3 mL) under argon atmosphere were added MCPBA (1.7 mmol),
I₂ (0.1 mmol), and p-TsOH˙H₂O (1.5 mmol). The resulting solution was stirred at r.t. until the color of I₂ faded completely (1-2 h). Then, a solution of acetophenone (1 mmol) in MeCN (2 mL) was added, and the mixture was stirred for 5 h at 60 ˚C under argon atmosphere. After the reaction, the reaction mixture was poured into a solution of sat. aq NaHCO₃ and Na₂SO₃, and the whole was extracted with CHCl₃ (3 × 20 mL). The organic layer was dried over Na₂SO₄. After removal of solvent under reduced pressure, α-tosyloxyacetophenone was obtained in the crude state. Pure α-tosyloxyacetophenone was obtained in 70% yield (204 mg) by short flash column chromatography on silica gel (EtOAc-hexane = 1:3).
α-Tosyloxyacetophenone Mp 90 ˚C (lit.^¹h mp 90-91 ˚C). IR (KBr): 1180, 1360, 1715 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.45 (s, 3 H), 5.27 (s, 2 H), 7.35 (d, J = 8.5 Hz, 2 H), 7.47 (t, J = 8.2 Hz, 2 H), 7.61 (t, J = 8.2 Hz, 1 H), 7.84 (d, J = 8.2 Hz, 2 H), 7.85 (d, J = 8.2 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 21.67, 69.90, 127.97, 128.13, 128.89, 129.89, 132.57, 133.71, 134.19, 145.28, 190.26.
α-Tosyloxy- p -methylacetophenone Mp 105 ˚C (lit.^¹¹ mp 82-83 ˚C). IR (KBr): 1170, 1350, 1700 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.41 (s, 3 H), 2.45 (s, 3 H), 5.24 (s, 2 H), 7.26 (d, J = 8.1 Hz, 2 H), 7.35 (d, J = 8.2 Hz, 2 H), 7.74 (d, J = 8.1 Hz, 2 H), 7.86 (d, J = 8.2 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 21.68, 21.77, 69.85, 128.07, 128.14, 129.57, 129.87, 131.24, 132.62, 145.23, 145.28, 189.80.
α-Tosyloxy- p -chloroacetophenone
Mp 123 ˚C (lit.^¹¹ mp 125 ˚C). IR (KBr): 1190, 1360, 1710 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.46 (s, 3 H), 5.21 (s, 2 H), 7.35 (d, J = 8.4 Hz, 2 H), 7.45 (d, J = 8.6 Hz, 2 H), 7.80 (d, J = 8.6 Hz, 2 H), 7.84 (d, J = 8.4 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 21.71, 69.79, 128.14, 129.28, 129.48, 129.94, 132.05, 132.44, 140.78, 145.43, 189.55.
α-Tosyloxy- p -nitroacetophenone Mp 137 ˚C (lit.^¹¹ mp 130-131 ˚C). IR (KBr): 1180, 1340, 1710 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.47 (s, 3 H), 5.25 (s, 2 H), 7.37 (d, J = 8.3 Hz, 2 H), 7.83 (d, J = 8.3 Hz, 2 H), 8.03 (d, J = 8.9 Hz, 2 H), 8.32 (d, J = 8.9 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 21.83, 70.04, 117.70, 124.17, 128.26, 129.45, 130.15, 132.32, 138.29, 145.81, 189.87.
α-Tosyloxy- m -nitroacetophenone Mp 129-130 ˚C. IR (KBr): 1615, 1375, 1348, 1188 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.46 (s, 3 H), 5.25 (s, 2 H), 7.37 (d, J = 8.0 Hz, 2 H), 7.72 (t, J = 8.0 Hz, 1 H), 7.84 (d, J = 8.0 Hz, 2 H), 8.21 (dt, J = 8.0, 1.2 Hz, 1 H), 8.46 (dt, J = 8.0, 1.2 Hz, 1 H), 8.63 (t, J = 1.2 Hz, 1 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 30.38, 69.87, 123.05, 128.15, 128.25, 130.03, 130.25, 132.35, 133.72, 135.29, 144.70, 145.88, 188.82. ESI-HRMS: m/z calcd for C₁₅H₁₃O₆NSNa [M + Na]: 358.0356; found: 358.0347.
α-Tosyloxypropiophenone Mp 68 ˚C (lit.^¹¹ mp 68-69 ˚C). IR (KBr): 1170, 1370, 1700 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 1.60 (d, J = 7.0 Hz, 3 H), 2.41 (s, 3 H), 5.79 (q, J = 7.0 Hz, 1 H), 7.29 (d, J = 8.1 Hz, 2 H), 7.46 (t, J = 7.2 Hz, 2 H), 7.75 (d, J = 7.2 Hz, 2 H), 7.88 (d, J = 8.1 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 18.84, 21.74, 128.04, 128.84, 129.85, 133.51, 133.77, 133.93, 143.48, 143.69, 145.10, 194.93.
α-(Tosyloxy)octyl Phenyl Ketone Mp 59-61 ˚C (lit.^²d mp 59-61 ˚C). IR (neat): 1180, 1340, 1700 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 0.86 (t, J = 6.9 Hz, 3 H), 1.20-1.43 (m, 10 H), 1.84-1.91 (m, 2 H), 2.40 (s, 3 H), 5.59 (dd, J = 8.2, 4.8 Hz, 1 H), 7.24 (d, J = 8.0 Hz, 2 H), 7.45 (t, J = 7.5 Hz, 2 H), 7.59 (t, J = 7.5 Hz, 1 H), 7.74 (d, J = 8.2 Hz, 2 H), 7.86 (d, J = 8.2 Hz, 2 H).
Tosyloxymethyl Naphthyl Ketone
Oil (lit.^¹²). IR (neat): 1176, 1365, 1700 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.40 (s, 3 H), 5.27 (s, 2 H), 7.29 (d, J = 8.4 Hz, 2 H), 7.50 (t, J = 8.3 Hz, 1 H), 7.53-7.60 (m, 2 H), 7.78 (dd, J = 1.2, 7.4 Hz, 1 H), 7.81 (d, J = 8.3 Hz, 2 H), 7.87 (d, J = 7.8 Hz, 1 H), 8.04 (d, J = 8.3 Hz, 1 H), 8.48 (dd, J = 0.9, 8.3 Hz, 1 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 21.65, 70.99, 124.13, 125.35, 126.82, 128.08, 128.34, 128.44, 128.50, 129.87, 130.16, 131.28, 132.60, 133.91, 134.05, 145.24, 193.91.
2,4,6-Trimethylphenyl (Tosyloxy)methyl Ketone Mp 58 ˚C. IR (neat): 1191, 1377, 1608 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.12 (s, 6 H), 2.27 (s, 3 H), 2.45 (s, 3 H), 4.84 (s, 2 H), 6.81 (s, 2 H), 7.33 (d, J = 8.0 Hz, 2 H), 7.87 (d, J = 8.0 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 18.96, 21.08, 21.65, 72.28, 128.05, 128.61, 129.81, 132.70, 133.83, 134.70, 139.82, 145.19, 201.17. ESI-HRMS: m/z calcd for C₁₈H₂₁O₄SNa [M + Na]: 355.0980; found: 355.0946.
2-Furyl (Tosyloxy)methyl Ketone Mp 63-64 ˚C (lit.^¹h mp 65-67 ˚C). IR (KBr): 1695, 1370, 1170, 810, 750 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.45 (s, 3 H), 5.09 (s, 2 H), 6.58 (dd, J = 3.7, 1.7 Hz, 1 H), 7.33 (dd, J = 3.7, 0.7 Hz, 1 H), 7.36 (d, J = 8.2 Hz, 2 H), 7.61 (dd, J = 1.7, 0.7 Hz, 1 H), 7.86 (d, J = 8.2 Hz, 2 H).
2-Thienyl (Tosyloxy)methyl Ketone Mp 92-93 ˚C (lit.^¹i mp 94-96 ˚C). IR (KBr): 1685, 1370, 1180, 730 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.45 (s,
3 H), 5.09 (s, 2 H), 7.16 (dd, J = 5.0, 3.9 Hz, 1 H), 7.35 (d, J = 8.1 Hz, 2 H), 7.73 (dd, J = 5.0, 1.0 Hz, 1 H), 7.79 (dd, J = 3.9, 1.0 Hz, 1 H), 7.85 (d, J = 8.1 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 21.66, 69.87, 128.17, 128.46, 129.94, 132.38, 133.13, 135.12, 140.12, 145.43, 183.64.
Ethyl α-Tosyloxybenzoylacetate Oil. IR (neat): 1440, 1590, 1690 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 1.18 (t, J = 7.0 Hz, 3 H), 2.85 (s, 3 H), 4.18 (m, 2 H), 5.59 (s, 1 H), 7.30 (d, J = 8.4 Hz, 2 H), 7.46 (t, J = 7.5 Hz, 2 H), 7.61 (t, J = 7.5 Hz, 1 H), 7.79 (d, J = 8.5 Hz, 2 H), 7.93 (d, J = 8.5 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 13.75, 21.63, 62.80, 78.03, 128.24, 128.71, 129.34, 129.82, 132.34, 133.28, 134.36, 145.68, 164.12, 188.19. HRMS-FAB: m/z calcd for C₁₈H₁₉O₆S [M + 1]: 363.0902; found: 363.0920.
Methyl α-Tosyloxyacetoacetate Oil. IR (neat): 1180, 1320, 1720 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 2.30 (s, 3 H), 2.48 (s, 3 H), 3.71 (s, 3 H), 5.20 (s, 1 H), 7.38 (d, J = 8.5 Hz, 2 H), 7.83 (d, J = 8.5 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 21.66, 26.53, 53.27, 80.34, 128.18, 129.98, 132.02, 145.90, 163.86, 196.98. HRMS-FAB: m/z calcd for C₁₂H₁₅O₆S [M + 1]: 287.0589; found: 287.0596.
2-Tosyloxy-3-pentanone Mp 45-46 ˚C (lit.^¹k mp 43-44 ˚C). IR (neat): 1190, 1360, 1720 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 1.03 (t, J = 7.3 Hz, 3 H), 1.35 (d, J = 7.0 Hz, 3 H), 2.47 (s, 3 H), 2.60 (m, 2 H), 4.80 (q, J = 7.0 Hz, 1 H), 7.37 (d, J = 8.0 Hz, 2 H), 7.81 (d, J = 8.0 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 6.96, 17.58, 21.65, 31.16, 80.68, 127.85, 129.99, 133.16, 145.29, 207.81.

5-Tosyloxy-6-undecanone Mp 72 ˚C (lit.^²d mp 72 ˚C). IR (neat): 1190, 1380, 1720 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 0.70-0.80 (m, 3 H), 0.86-1.75 (m, 15 H), 2.46 (s, 3 H), 2.51 (t, J = 7.5 Hz, 2 H), 4.64 (dd, J = 8.0, 4.6 Hz, 1 H), 7.36 (d, J = 8.0 Hz, 2 H), 7.80 (d, J = 8.0 Hz, 2 H). 1-Tosyloxy-2-octanone Oil. IR (neat): 1180, 1360, 1590, 1730 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 0.87 (t, J = 7.0 Hz, 3 H), 1.20-1.32 (m, 6 H), 1.48-1.62 (m, 2 H), 2.45 (s, 3 H), 2.49 (t, J = 7.2 Hz, 2 H), 4.49 (s, 2 H), 7.37 (d, J = 8.0 Hz, 2 H), 7.82 (d, J = 8.0 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 13.97, 21.68, 22.39, 22.76, 28.62, 31.43, 38.98, 71.78, 128.04, 130.00, 132.30, 145.44, 203.43. HRMS-FAB: m/z calcd for C₁₅H₂₃O₄S [M + 1]: 299.1317; found: 299.1295.
3-Tosyloxy-2-octanone Oil. IR (neat): 1180, 1360, 1600, 1740 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 0.80 (t, J = 7.3 Hz, 3 H), 1.00-1.30 (m,
6 H), 1.54-1.78 (m, 2 H), 2.23 (s, 3 H), 2.48 (s, 3 H), 4.58 (dd, J = 8.4, 4.6 Hz, 1 H), 7.36 (d, J = 8.7 Hz, 2 H), 7.81 (d, J = 8.7 Hz, 2 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 13.91, 21.97, 22.35, 24.17, 26.01, 31.00, 31.52, 84.62, 128.13, 130.07, 132.98, 145.48, 205.78. HRMS-FAB: m/z calcd for C₁₅H₂₃O₄S [M + 1]: 299.1317; found: 299.1315.