10.1002/hlca.201900164
Helvetica Chimica Acta
HELVETICA
2,3-Diphenyloxirane (1m) was prepared from 1,2-diphenylethene using the
MCPBA epoxidation reaction.[17] To a solution of 1,2-diphenylethene (900
mg, 5.0 mmol) in DCM (20 mL) in a 100 mL flask was added MCPBA (1.5 g,
7.5 mmol, 85%) at 0 °C. The reaction mixture was allowed to stir at room
temperature overnight. The solution was then washed with NaHCO3 aq (20
mL) and dried over Na2SO4. After evaporation of the solvent, the crude
product was purified on silica gel column chromatography with a mixture of
petroleum ether/EtOAc (20:1, v/v) to afford the desired epoxide 1m.
Epoxide 1n is commercial available. Epoxides 1a-1e and 1i-1m are known
compounds.
2-Methyl-2-phenyloxirane (1a).[18] Colorless liquid. 482 mg, yield 72%. Rf =
0.64, 20% ethyl acetate in petroleum ether. 1H NMR (400 MHz, CDCl3) δ
7.36–7.11 (m, 5H), 2.89 (d, J = 5.4 Hz, 1H), 2.72 (d, J = 5.4 Hz, 1H), 1.64 (s, 3H).
13C NMR (101 MHz, CDCl3) δ 141.1, 128.3, 127.4, 125.3, 64.9, 57.0, 21.8.
2-(4-Bromophenyl)-2-methyloxirane (1b).[28,29] Colorless oil. 0.934 g, yield
88%. Rf = 0.71, 20% ethyl acetate in petroleum ether. 1H NMR (400 MHz,
CDCl3) δ 7.44 (d, J = 8.4 Hz, 2H), 7.22 (d, J = 8.4 Hz, 2H), 2.95 (d, J = 5.4 Hz,
1H), 2.73 (d, J = 5.3 Hz, 1H), 1.68 (s, 1H). 13C NMR (101 MHz, CDCl3) δ 140.3,
131.4, 127.1, 121.4, 56.9, 56.3, 21.5.
2,2-Diphenyloxirane (1j).[18] White crystals. m.p. 54-56 °C. (Lit.[18] M.p.
55−56 C). 1.0 g, yield 51%. Rf = 0.75, 20% ethyl acetate in petroleum ether.
1H NMR (400 MHz, CDCl3) δ 7.39–7.27 (m, 10H), 3.27 (s, 2H). 13C NMR (101
MHz, CDCl3) δ 139.6, 129.2, 129.0, 128.3, 128.0, 127.5, 61.84, 56.9.
2-Methyl-2-phenethyloxirane (1k).[28,29] Colorless liquid. 240 mg, yield
30%. Rf = 0.85, 20% ethyl acetate in petroleum ether. 1H NMR (400 MHz,
CDCl3) δ 7.27 (dd, J = 7.8, 7.3 Hz, 2H), 7.19 (d, J = 7.0 Hz, 1H), 7.18 (d, J = 7.7
Hz, 2H), 2.74–2.68 (m, 2H), 2.58 (dd, J = 11.0, 4.9 Hz, 2H), 1.97–1.77 ( m, 2H),
1.37 (s, 3H).13C NMR (101 MHz, CDCl3) δ 141.6, 128.4, 128.2, 125.9, 56.6, 53.9,
38.5, 31.4, 21.0.
(E)-2-Methyl-2-styryloxirane (1l).[34] Colorless liquid.480 mg, 60%. Rf
=
0.85, 20% ethyl acetate in petroleum ether. 1H NMR (400 MHz, CDCl3) δ
7.35–7.14 (m, 5H), 6.82–6.46 (m, 1H), 5.94 (d, J = 16.2 Hz, 1H), 2.83 (d, J = 5.2
Hz, 1H), 2.77 (d, J = 5.2 Hz, 1H), 1.50 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 136.3,
131.6, 130.6, 128.6, 127.8, 126.4, 67.9, 56.2, 19.8.
2,3-Diphenyloxirane (1m).[35] Colorless crystals. M. p. 68–70 C. (Lit.[36] M.p.
67−69 C). 0.945 g, yield 48%. Rf = 0.82, 20% ethyl acetate in petroleum
ether. 1H NMR (400 MHz, CDCl3) δ 7.50–7.14 (m, 10H), 3.87 (s, 2H). 13C NMR
(101 MHz, CDCl3) δ 137.1, 128.6, 128.3, 125.5, 62.8.
4-(2-Methyloxiran-2-yl)benzonitrile (1c).[30] Colorless liquid. 490 mg, yield
62%. Rf = 0.50, 20% ethyl acetate in petroleum ether. 1H NMR (400 MHz,
CDCl3) δ 7.63 (d, J = 8.5 Hz, 2H), 7.48 (d, J = 8.5 Hz, 2H), 3.03 (d, J = 5.3 Hz,
1H), 2.76 (d, J = 5.3 Hz, 1H), 1.74 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 146.5,
132.1, 126.0, 118.5, 111.2, 57.0, 56.1, 21.0.
2-(4-Methoxyphenyl)-2-methyloxirane (1d).[31] Colorless liquid. 400 mg,
yield 49%. Rf = 0.70, 20% ethyl acetate in petroleum ether. 1H NMR (400
MHz, CDCl3) δ 7.28 (d, J = 8.8 Hz, 2H), 6.86 (d, J = 8.8 Hz, 2H), 3.78 (s, 3H),
2.94 (d, J = 5.4 Hz, 1H), 2.78 (d, J = 5.3 Hz, 1H), 1.68 (s, 3H).13C NMR (101 MHz,
CDCl3) δ 158.9, 133.2, 126.5, 113.6, 56.9, 56.4, 55.2, 21.9.
General procedure for the retro-Corey-Chaykovsky epoxidation of
epoxides 1
Epoxide 1 (0.5 mmol) was dissolved in 2 mL of mesitylene in a 10 mL
reaction tube. After DABCO (112 mg, 1.0 mmol) was added at room
temperature, the reaction mixture was heated at 165 C for 48 h. After
cooling to room temperature, the reaction mixture was directly subjected
to flash column chromatography with ethyl acetate/petroleum ether (1:50,
v/v) to afford product 2. All ketones are known products.
2-Phenyl-2-styryloxirane (1e).[32] Colorless liquid. 1.6 g, yield 72%. Rf = 0.75,
20% ethyl acetate in petroleum ether. 1H NMR (400 MHz, CDCl3) δ 7.60–7.43
(m, 2H), 7.43–7.21 (m, 8H), 6.62–6.47 (m, 1H), 6.45–6.32 (m, 1H), 3.21 (dd, J
= 5.5, 2.0 Hz, 1H), 3.12 (dd, J = 5.5, 2.0 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ
138.3, 136.2, 133.8, 128.7, 128.6, 128.3, 128.0, 127.9, 127.1, 126.5, 60.4, 57.2.
(E)-2-(4-Chlorophenyl)-2-styryloxirane (1f). Colorless oil. 152 mg, yield
20%. Rf = 0.80, 20% ethyl acetate in petroleum ether. 1H NMR (400 MHz,
CDCl3) δ 7.41–7.26 (m, 9H), 6.53 (d, J = 16.0 Hz, 1H), 6.33 (d, J = 16.0 Hz, 1H),
3.21 (d, J = 5.6 Hz, 1H), 3.07 (d, J = 5.6 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ
136.8, 135.9, 134.2, 128.9, 128.6, 128.6, 128.2, 128.1, 127.2, 126.6, 126.5,
59.9, 57.2. HRMS (ESI) m/z: calcd. for C16H14ClO+[M+H]+: 257.0728; found:
257.0728.
Phenylethan-1-one (2a).[37] Purified by flash column chromatography
(PE/EA 50:1, v/v) on silica gel to give the desired product as colorless oil, 19
mg, 31% yield Rf = 0.27, 5% ethyl acetate in petroleum ether. 1H NMR (400
MHz, CDCl3) δ 8.02–7.92 (m, 2H), 7.57 (t, J = 7.6 Hz, 1H), 7.47 (dd, J = 7.6 7.6,
Hz, 2H), 2.61 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 198.1, 137.0, 133.0, 128.5,
128.2, 26.5.
1-(4-Bromophenyl)ethan-1-one (2b).[38] Purified by flash column
chromatography (PE/EA 50:1, v/v) on silica gel to give the desired product
as white solid, 28 mg, 28% yield. M.p. 57–58 C. (Lit.[39] M.p. 52−53 C). Rf =
1
0.30, 6.67% ethyl acetate in petroleum ether. H NMR (400 MHz, CDCl3) δ
7.82 (d, J = 8.5 Hz, 2H), 7.61 (d, J = 8.5 Hz, 2H), 2.59 (s, 3H). 13C NMR (101
MHz, CDCl3) δ 197.0, 135.8, 131.9, 129.8, 128.3, 26.5.
4-Acetylbenzonitrile (2c).[40] Purified by flash column chromatography
(PE/EA 50:1, v/v) on silica gel to give the desired product as white solid. 15
mg, 21% yield. M.p. 60–63 C. (Lit.[41] M.p. 59−60 C). Rf = 0.14, 10% ethyl
acetate in petroleum ether. 1H NMR (400 MHz, CDCl3) δ 8.05 (d, J = 8.4 Hz,
2H), 7.79 (d, J = 8.4 Hz, 2H), 2.66 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 196.4,
139.8, 132.4, 128.6, 117.8, 116.3, 26.7.
(E)-2-(2-Chlorostyryl)-2-phenyloxirane (1g). Yellow oil. 703 mg, yield 92%.
1
Rf = 0.65, 20% ethyl acetate in petroleum ether. H NMR (400 MHz, CDCl3)
δ 7.53 (d, J = 7.5 Hz, 1H), 7.48 (dd, J = 7.1, 1.2 Hz, 2H), 7.42 – 7.30 (m, 4H), 7.24
– 7.12 (m, 2H), 6.97 (d, J = 16.0 Hz, 1H), 6.38 (d, J = 16.0 Hz, 1H), 3.23 (d, J =
5.6 Hz, 1H), 3.13 (d, J = 5.6 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ 138.0, 134.5,
133.2, 131.5, 130.1, 129.7, 129.0, 128.4, 128.0, 127.0, 126.9, 126.8, 60.3, 57.3.
HRMS (ESI) m/z: calcd. for C16H14ClO+[M+H]+: 257.0728; found: 257.0726.
(E)-2-(3-Fluorostyryl)-2-phenyloxirane (1h). Colorless liquid. 697 mg, yield
97%. Rf = 0.70, 20% ethyl acetate in petroleum ether. 1H NMR (400 MHz,
CDCl3) δ 7.40–7.19 (m, 5H), 7.17–7.10 (m, 1H), 6.96 (ddd, J = 10.2, 9.2, 4.7 Hz,
2H), 6.82 (td, J = 8.3, 2.0 Hz, 1H), 6.41 (d, J = 16.0 Hz, 1H), 6.29 (d, J = 16.0
Hz, 1H), 3.08 (d, J = 5.6 Hz, 1H), 3.01 (d, J = 5.6 Hz, 1H). 13C NMR (101 MHz,
CDCl3) δ 163.0 (d, J = 245.6 Hz), 138.5 (d, J = 7.7 Hz), 137.9, 132.5 (d, J = 1.9
Hz), 130.0 (d, J = 8.4 Hz), 128.4, 128.0, 127.1, 122.4 (d, J = 2.2 Hz), 114.8 (d, J
= 21.4 Hz), 112.9 (d, J = 21.9 Hz), 60.2, 57.2. 19F NMR (377 MHz, CDCl3) δ -
113.23.HRMS (ESI) m/z: calcd. for C16H14FO+[M+H]+: 241.1023; found:
241.1021.
1-(4-Methoxyphenyl)ethan-1-one (2d).[42] Purified by flash column
chromatography (PE/EA 50:1, v/v) on silica gel to give the desired product
as colorless oil, 10 mg, 13% Rf = 0.18, 6.67% ethyl acetate in petroleum ether.
1H NMR (400 MHz, CDCl3) δ 7.94 (d, J = 8.8 Hz, 2H), 6.93 (d, J = 8.8 Hz, 2H),
3.87 (s, 3H), 2.56 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 196.8, 163.5, 130.6,
130.3, 113.7, 55.5, 26.3.
Chalcone (2e).[43] Purified by flash column chromatography (PE/EA 100:1,
v/v) on silica gel to give the desired product as white crystals. m.p. 55–57 C.
(Lit.[44] M.p. 55−56 C) 61 mg, 59% yield. Rf = 0.65, 20% ethyl acetate in
petroleum ether. 1H NMR (400 MHz, CDCl3) δ 8.02 (dd, J = 7.2, 1.4 Hz, 2H),
7.81 (d, J = 15.7 Hz, 1H), 7.64 (dd, J = 6.7, 2.8 Hz, 2H), 7.58–7.47 (m, 4H), 7.43–
7.39 (m, 3H). 13C NMR (101 MHz, CDCl3) δ 190.5, 144.8, 138.2, 134.9, 132.7,
130.5, 128.9, 128.6, 128.5, 128.4, 122.1.
2-Phenyl-2-(phenylethynyl)oxirane (1i).[33] Yellow oil. 500 mg, yield 45%.
1
Rf = 0.90, 20% ethyl acetate in petroleum ether. H NMR (400 MHz, CDCl3)
(E)-1-(4-Chlorophenyl)-3-phenylprop-2-en-1-one (2f).[45] Purified by flash
column chromatography (PE/EA 100:1, v/v) on silica gel to give the desired
product as light yellow solid m.p. 95–97 C. (Lit.[45] M.p. 93−96 C) 73mg,
yield 61%. Rf = 0.7, 20% ethyl acetate in petroleum ether. 1H NMR (400 MHz,
δ 7.59–7.54 (m, 2H), 7.51 (ddd, J = 4.9, 1.9, 0.6 Hz, 2H), 7.38 (t, J = 7.3 Hz, 2H),
7.35–7.28 (m, 4H), 3.52 (d, J = 6.1 Hz, 1H), 3.10 (d, J = 6.1 Hz, 1H). 13C NMR
(101 MHz, CDCl3) δ 137.2, 132.0, 131.8, 128.8, 128.4, 128.4, 128.3, 125.6,
121.9, 86.6, 84.3, 59.4, 51.4.
4
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