Z.-W. Chen et al. / Tetrahedron 69 (2013) 6116e6120
6119
coordinates with the triple bond of the terminal alkyne and forms
-complex A. In route I, the nucleophile eOH attacks the complex
NMR (100 MHz, CDCl3):
31.0, 26.5. MS (EI) m/z: 176, 161, 133, 118, 91, 77.
d
¼197.9, 156.8, 134.6, 128.2, 125.5, 35.1,
a
p
to generate enol intermediate B, which subsequently undergoes
ketoeenol tautomerism to produce C, and the intermediate C
would generate methyl ketone 2 by protonation. In route II, the
nucleophile acetic anion attacks the complex to provide in-
termediate D, and then protonation to form enol acetate E, which
subsequently undergoes successive hydrolysis and ketoeenol tau-
tomerism to generate methyl ketone 2.
4.2.5. 1-([1,10-Biphenyl]-4-yl)ethanone (2e). 1H NMR (400 MHz,
CDCl3):
7.45e7.49 (m, 2H), 7.38e7.42 (m, 1H), 2.64 (s, 3H). 13C NMR
(100 MHz, CDCl3):
¼197.8, 145.7, 139.8, 135.8, 128.9, 128.9, 128.2,
127.2, 127.2, 26.6. MS (EI) m/z: 196, 181, 152, 76, 43.
d¼8.02e8.05 (m, 2H), 7.67e7.70 (m, 2H), 7.61e7.64 (m, 2H),
d
4.2.6. 1-(40-Propyl-[1,10-biphenyl]-4-yl)ethanone (2f). 1H
NMR
(400 MHz, CDCl3):
d
¼8.00e8.03 (m, 2H), 7.66e7.69 (m, 2H),
7.54e7.56 (m, 2H), 7.28 (d, J¼8.4 Hz, 2H), 2.64 (t, J¼7.6 Hz, 2H),
3. Conclusions
2.63 (s, 3H), 1.64e1.73 (m, 2H), 0.98 (t, J¼7.2 Hz, 3H). 13C NMR
(100 MHz, CDCl3):
d
¼197.7, 145.7, 143.0, 137.1, 135.5, 129.1, 128.9,
In conclusion, we have presented a general and facile method for
the synthesis of methyl ketones from the simple terminal alkynes in
high yields with excellent regioselectivity. The silver-catalyzed func-
tionalization reaction tolerated a variety of functional groups. The
proposed mechanism indicates that enol acetate may be the in-
termediate in this transformation. Further utilization of this pro-
cedure and understanding the mechanism will continue in our
laboratory.
127.1, 126.9, 37.7, 26.6, 24.5, 13.8. MS (EI) m/z: 238, 223, 209, 165,
152, 115, 76, 43.
4.2.7. 1-(4-Methoxyphenyl)ethanone (2g). 1H NMR (400 MHz,
CDCl3):
d
¼7.91 (d, J¼8.8 Hz, 2H), 6.90 (d, J¼8.8 Hz, 2H), 3.84 (s,
3H), 2.52 (s, 3H). 13C NMR (100 MHz, CDCl3):
d
¼196.7, 163.4,
130.5, 130.3, 113.6, 55.4, 26.3. MS (EI) m/z: 150, 135, 107, 92, 77,
63.
4.2.8. 1-(3-Methoxyphenyl)ethanone (2h). 1H NMR (400 MHz,
4. Experimental
4.1. General
CDCl3):
d
¼7.41e7.47 (m, 2H), 7.26e7.31 (m, 1H), 7.02e7.04 (m, 1H),
3.77 (s, 3H), 2.51 (s, 3H). 13C NMR (100 MHz, CDCl3):
d
¼197.7, 159.7,
138.4, 129.5, 121.0, 119.4, 112.3, 55.3, 26.6. MS (EI) m/z: 150, 135, 107,
92, 77, 63.
1H and 13C NMR spectra were obtained on a 400 MHz NMR
spectrometer. The chemical shifts are referenced to signals at 7.26
and 77.0 ppm, respectively, chloroform is solvent with TMS as the
internal standard. Mass spectra were recorded on a GCeMS spec-
trometer at an ionization voltage of 70 eV equipped with a DB-WAX
capillary column (internal diameter: 0.25 mm, length: 30 m). All
the other chemicals were purchased from Aldrich Chemicals.
4.2.9. 1-(2-Methoxyphenyl)ethanone (2i). x1H NMR (400 MHz,
CDCl3):
d
¼7.69e7.72 (m, 1H), 7.41 (m, 1H), 6.93e6.98 (m, 2H), 3.88
(s, 3H), 2.59 (s, 3H). 13C NMR (100 MHz, CDCl3):
d
¼199.8, 158.9,
133.6, 130.3, 128.2, 120.5, 111.6, 55.4, 31.8. MS (EI) m/z: 150, 135, 105,
92, 77, 63.
4.2.10. 1-(Naphthalen-1-yl)ethanone (2j). 1H NMR (400 MHz,
CDCl3):
J¼7.2 Hz, 1H), 7.86 (d, J¼7.6 Hz, 1H), 7.58e7.62 (m, 1H), 7.45e7.54
(m, 2H), 2.72 (s, 3H). 13C NMR (100 MHz, CDCl3):
d
¼8.78 (d, J¼8.4 Hz, 1H), 7.97 (d, J¼8.0 Hz, 1H), 7.91 (d,
4.2. General procedure for the synthesis of methyl ketones
(2aex)
d¼201.8, 135.4,
134.0, 133.0, 130.1, 128.7, 128.4, 128.0, 126.4, 126.0, 124.3, 29.9. MS
To the mixture of terminal alkyne (1 mmol), water (2.0 equiv),
and acetic acid (2 mL), silver tetrafluoroborate (5 mol %) was added.
The mixture was stirred at 110 ꢀC for 10 h. Water (10 mL) was added
and the solution was extracted with ethyl acetate (3ꢁ8 mL), the
combined extract was dried with anhydrous MgSO4. The solvent
was removed and the crude product was separated by column
chromatography to give the pure sample.
(EI) m/z: 170, 155, 127, 101, 77, 51.
4.2.11. 1-(4-Fluorophenyl)ethanone (2k). 1H NMR (400 MHz,
CDCl3):
NMR (100 MHz, CDCl3):
130.8, 115.7, 115.4, 26.4. MS (EI) m/z: 138, 123, 95, 75.
d
¼7.92e7.95 (m, 2H), 7.06e7.10 (m, 2H), 2.54 (s, 3H). 13C
d
¼196.4, 166.9, 164.4, 133.6, 133.5, 130.9,
4.2.12. 1-(4-Chlorophenyl)ethanone (2l). 1H NMR (400 MHz,
4.2.1. Acetophenone (2a). 1H NMR (400 MHz, CDCl3):
(m, 2H), 7.53e7.58 (m, 1H), 7.44e7.47 (m, 2H), 2.60 (s, 3H). 13C NMR
d¼7.94e7.96
CDCl3):
13C NMR (100 MHz, CDCl3):
MS (EI) m/z: 154, 139, 111, 74.
d
¼7.82 (d, J¼8.4 Hz, 2H), 7.36 (d, J¼8.4 Hz, 2H), 2.52 (s, 3H).
d
¼196.7, 139.4, 135.4, 129.6, 128.8, 26.4.
(100 MHz, CDCl3):
z: 120, 105, 71, 51.
d¼198.1,137.1,133.1, 128.5, 128.3, 26.6. MS (EI) m/
4.2.13. 1-(4-Bromophenyl)ethanone (2m). 1H NMR (400 MHz,
CDCl3):
¼7.80 (d, J¼8.4 Hz, 2H), 7.58 (d, J¼8.4 Hz, 2H), 2.56 (s, 3H).
13C NMR (100 MHz, CDCl3):
4.2.2. 1-(p-Tolyl)ethanone (2b). 1H NMR (400 MHz, CDCl3):
d
¼7.84
d
(d, J¼8.0 Hz, 2H), 7.24 (d, J¼8.0 Hz, 2H), 2.56 (s, 3H), 2.39 (s, 3H). 13C
d
¼196.9, 135.8, 131.8, 129.8, 128.2, 26.5.
NMR (100 MHz, CDCl3):
d¼197.8, 143.8, 134.7, 129.2, 128.4, 26.4,
MS (EI) m/z: 198, 183, 155, 104, 75.
21.5. MS (EI) m/z: 134, 119, 91, 65.
4.2.14. 1-(2-Bromophenyl)ethanone (2n). 1H NMR (400 MHz,
4.2.3. 1-(m-Tolyl)ethanone (2c). 1H NMR (400 MHz, CDCl3):
d
¼7.75
CDCl3):
d
¼7.59e7.61 (m, 1H), 7.44e7.46 (m, 1H), 7.34e7.38 (m, 1H),
(d, J¼10.8 Hz, 2H), 7.33 (t, J¼8.0 Hz, 2H), 2.58 (s, 3H), 2.40 (s, 3H). 13C
7.26e7.30 (m, 1H), 2.62 (s, 3H). 13C NMR (100 MHz, CDCl3):
d
¼201.3,
NMR (100 MHz, CDCl3):
d¼198.4, 138.3, 137.4, 133.8, 128.7, 128.4,
141.5, 133.8, 131.7, 128.9, 127.4, 118.9, 30.3. MS (EI) m/z: 198, 183,
155, 104, 75, 51.
125.5, 26.6, 21.3. MS (EI) m/z: 134, 119, 91, 65, 51.
4.2.4. 1-(4-(tert-Butyl)phenyl)ethanone (2d). 1H NMR (400 MHz,
4.2.15. 1-(4-(Trifluoromethyl)phenyl)ethanone (2o). 1H NMR (40
CDCl3):
d
¼7.91 (t, J¼3.0 Hz, 1H), 7.89 (t, J¼3.0 Hz, 1H), 7.49 (t,
0 MHz, CDCl3):
d
¼8.06 (d, J¼8.0 Hz, 2H), 7.73 (d, J¼8.0 Hz, 2H), 2.65
J¼3.0 Hz, 1H), 7.46 (t, J¼3.0 Hz, 1H), 2.58 (s, 3H), 1.34 (s, 9H). 13C
(s, 3H). 13C NMR (100 MHz, CDCl3):
d
¼196.9, 139.6, 134.2, 134.2, 128.6,