4.1.3. General method II: Preparation of 2-azetidinones 7a–7u, 8a–8k
To a stirring, refluxing solution of the imine (5 mmol) and triethylamine (6 mmol) in anhydrous dichloromethane (40 mL), a solution of crotonyl chloride (6 mmol) in anhydrous dichloromethane (10 mL) was injected dropwise through a rubber septum over 45 min under nitrogen. The reaction was heated at reflux for 5 h and stirred at room temperature overnight, continuously under nitrogen. The reaction mixture coled and washed with water (2 × 100 mL), with the organic layer being retained each time. The reaction was dried over anhydrous sodium sulfate and the solvent was then removed under reduced pressure. The crude product was purified by flash chromatography over silica gel (eluent: n-hexane: ethyl acetate, 4:1).
4-(4-Fluorophenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7a)
Preparation as described above from crotonyl chloride and (4-fluorobenzylidene)-3,4,5-trimethoxyphenylamine (5a). The product was obtained as yellow solid, yield 36%, Mp 147–149 °C. IR (KBr) νmax: 1749 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.73 (s, 6H), 3.74–3.75 (m, 1H), 3.78 (s, 3H), 4.78 (d, J = 2.52 Hz, 1H), 5.35–5.43 (m, 2H), 5.99–6.08 (m, 1H), 6.53 (s, 2H), 7.09–7.13 (m, 2H), 7.36–7.38 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 55.57, 60.51, 60.51, 63.51, 94.20, 115.76, 115.97, 119.74, 127.18, 127.25, 129.81, 132.63, 133.16, 134.09, 153.10, 161.10, 164.56. HRMS: found 356.1303 (M+-H); C20H19FNO4 requires 356.1298.
4-(4-Chlorophenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7b)
Preparation as described above from crotonyl chloride and (4-chlorobenzylidene)-(3,4,5-trimethoxyphenyl)amine (5b) to afford the product as a yellow solid, yield 30%, Mp 104 °C. IR (KBr) νmax: 1754 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.70–3.71 (m, 1H), 3.72 (s, 6H), 3.77 (s, 3H), 4.77 (d, J = 2.48 Hz, 1H), 5.33–5.41 (m, 2H), 5.97–6.06 (m, 1H), 6.51 (s, 2H), 7.32 (d, J = 6.52 Hz, 2H), 7.38 (d, J = 8.56 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 56.06, 60.88, 60.95, 63.93, 94.64, 120.30, 127.28, 129.50, 130.19, 133.55, 134.54, 134.59, 135.89, 153.58, 164.89. HRMS: found 372.1017 (M+-H); C20H1935ClNO4 requires 372.1003.
4-(4-Bromophenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7c)
Preparation as described above from crotonyl chloride and (4-bromobenzylidene)-3,4,5-trimethoxyphenylamine (5c) to afford the product as a brown oil, yield 48%. IR (NaCl) νmax: 1751 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.71–3.72 (m, 1H), 3.74 (s, 6H), 3.79 (s, 3H), 4.76 (d, J = 2.52 Hz, 1H), 5.35–5.43 (m, 2H), 5.99–6.08 (m, 1H), 6.53 (s, 2H), 7.27 (d, J = 8.52 Hz, 2H), 7.55 (d, J = 8.52 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 55.63, 60.50, 60.52, 63.43, 94.19, 119.88, 122.19, 127.08, 129.69, 132.01, 133.06, 135.95, 139.98, 153.13, 164.42. HRMS: found 418.0643 (M++H); C20H2179BrNO4 requires 418.0654.
4-(4-Nitrophenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7d)
Preparation as described above from crotonyl chloride and (4-nitrobenzylidene)-3,4,5-trimethoxyphenylamine (5d) to afford the product as a brown solid, yield 28%, Mp 132–133 °C. IR (KBr) νmax: 1754 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.73 (s, 6H), 3.75–3.76 (m, 1H), 3.78 (s, 3H), 4.92 (d, J = 2.48 Hz, 1H), 5.39–5.45 (m, 2H), 6.01–6.06 (m, 1H), 6.50 (s, 2H), 7.56 (d, J = 9.04 Hz, 2H), 8.28 (d, J = 9.04 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 55.68, 60.03, 60.52, 63.53, 94.16, 120.46, 124.14, 126.26, 129.24, 132.75, 134.44, 144.28, 147.61, 153.27, 163.83. HRMS: found 385.1389 (M++H); C20H21N2O6 requires 385.1400.
4-(4-Dimethylaminophenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7e)
Preparation as described above from crotonyl chloride and (4-(dimethylamino)benzylidene)-3,4,5-trimethoxyphenylamine (5e) to afford the product as a brown oil, yield 61%. IR (NaCl) νmax: 1746 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 2.98 (s, 6H), 3.73 (s, 6H), 3.77 (s, 3H), 3.78–3.92 (m, 1H), 4.70 (d, J = 2.00 Hz, 1H), 5.30–5.40 (m, 2H), 5.99–6.08 (m, 1H), 6.60 (s, 2H), 6.74 (d, J = 8.04 Hz, 2H), 7.27 (d, J = 9.04 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 40.01, 55.55, 60.49, 61.27, 63.30, 94.27, 112.20, 119.15, 126.67, 130.38, 133.58, 134.62, 137.93, 147.60, 152.95, 165.25. HRMS: found 381.1819 (M+-H); C22H25N2O4 requires 381.1814.
4-Phenyl-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7f)
Preparation as described above from crotonyl chloride and benzylidene-(3,4,5-trimethoxyphenyl)amine (5f) to afford the product as a yellow solid, yield 29%, Mp 109–111 °C. IR (KBr) νmax: 1750 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.72 (s, 6H), 3.78 (s, 3H), 3.80–3.81 (m, 1H), 4.79 (d, J = 2.52 Hz, 1H), 5.35–5.43 (m, 2H), 6.01–6.06 (m, 1H), 6.56 (s, 2H), 7.39–7.41 (m, 5H). 13C NMR (100 MHz, CDCl3): δ 55.54, 60.51, 61.22, 63.35, 94.22, 119.57, 125.44, 125.53, 128.31, 128.80, 130.02, 133.34, 133.97, 136.85, 153.04, 164.75. HRMS: found 338.1383 (M+-H); C20H20NO4 requires 338.1392.
4-p-Tolyl-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7g)
Preparation as described above from crotonyl chloride and (4-methylbenzylidene)-(3,4,5-trimethoxyphenyl)amine (5g) to afford the product as a yellow solid, yield 35%, Mp 106–107 °C. IR (KBr) νmax: 1746 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 2.37 (s, 3H), 3.72 (s, 6H), 3.75 (m, 1H), 3.77 (s, 3H), 4.76 (d, J = 2.04 Hz, 1H), 5.32–5.41 (m, 2H), 5.99–6.08 (m, 1H), 6.56 (s, 2H), 7.21 (d, J = 8.00 Hz, 2H), 7.28 (d, J = 8.00 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 20.76, 55.54, 60.49, 61.07, 63.39, 94.22, 119.44, 125.48, 129.45, 130.11, 133.40, 133.78, 133.92, 138.18, 153.01, 164.87. HRMS: found 354.1706 (M++H); C21H24NO4 requires 354.1705.
4-(4-Methoxyphenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7h)
Preparation as described above from crotonyl chloride and (4-methoxybenzylidene)-3,4,5-trimethoxyphenylamine (
5h) to afford the product as a brown oil, yield 34% [
98]. IR (NaCl) ν
max: 1747 (C=O) cm
−1.
1H NMR (400 MHz, CDCl
3): δ 3.64 (s, 6H), 3.67–3.68 (m, 1H), 3.69 (s, 3H), 3.72 (s, 3H), 4.70 (d,
J = 2.00 Hz, 1H), 5.22–5.32 (m, 2H), 5.91–6.00 (m, 1H), 6.51 (s, 2H), 6.85 (d,
J = 8.52 Hz, 2H), 7.26 (d,
J = 8.52 Hz, 2H).
13C NMR (100 MHz, CDCl
3): δ 55.37, 56.03, 60.97, 61.37, 63.92, 94.70, 114.61, 119.90, 127.31, 129.14, 130.58, 133.86, 133.93, 153.48, 159.90, 165.39. HRMS: found 370.1658 (M
++H); C
21H
24NO
5 requires 370.1654.
4-(4-Ethoxyphenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7i)
Preparation as described above from crotonyl chloride and (4-ethoxybenzylidene)-(3,4,5-trimethoxyphenyl)amine (
5i) to afford a colourless solid, yield 33%, Mp 92–93 °C. [
98] IR (KBr) ν
max: 1749 (C=O) cm
−1.
1H NMR (400 MHz, CDCl
3): δ 1.43 (t,
J = 6.84 Hz, 3H), 3.73 (s, 6H), 3.75–3.76 (m, 1H), 3.78 (s, 3H), 4.05 (q,
J = 6.86 Hz, 2H), 4.73 (d,
J = 2.48 Hz, 1H), 5.33–5.42 (m, 2H), 6.00–6.08 (m, 1H), 6.57 (s, 2H), 6.93 (d,
J = 8.80 Hz, 2H), 7.31 (d,
J = 8.80 Hz, 2H).
13C NMR (100 MHz, CDCl
3): δ 14.33, 55.55, 60.50, 60.94, 63.11, 63.43, 94.22, 114.65, 119.40, 126.83, 128.49, 130.14, 133.42, 133.90, 153.01, 158.81, 164.94 (C=O). HRMS: found 384.1819 (M
++H); C
22H
26NO
5 requires 384.1811.
4-(4-Butoxyphenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7j)
Preparation as described above from crotonyl chloride and (4-butoxybenzylidene)-3,4,5-trimethoxyphenylamine (5j) to afford a yellow solid, yield 40%, Mp 100–102 °C. IR (KBr) νmax: 1749 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 0.98 (t, J = 7.32 Hz, 3H), 1.45–1.54 (m, 2H), 1.74–1.81 (m, 2H), 3.72 (s, 6H), 3.73-3.74 (m, 1H), 3.77 (s, 3H), 3.97 (t, J = 6.84 Hz, 2H), 4.73 (d, J = 1.96 Hz, 1H), 5.31–5.40 (m, 2H), 6.00–6.05 (m, 1H), 6.56 (s, 2H), 6.92 (d, J = 7.84 Hz, 2H), 7.30 (d, J = 8.80 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 13.39, 18.77, 30.78, 55.53, 60.48, 60.93, 63.43, 67.33, 94.22, 114.66, 119.36, 126.80, 128.40, 130.15, 133.42, 133.89, 153.00, 159.03, 164.93. HRMS: found 412.2129 (M++H); C24H30NO5 requires 412.2124.
4-(4-Phenoxyphenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7k)
Preparation as described above from crotonyl chloride and (4-phenoxylbenzylidene)-(3,4,5-trimethoxyphenyl)amine (5k) to afford a pale yellow solid, yield 37%, Mp 128–130 °C. IR (KBr) νmax: 1749 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.75 (s, 6H), 3.77–3.78 (m, 1H), 3.79 (s, 3H), 4.78 (d, J = 2.52 Hz, 1H), 5.35–5.44 (m, 2H), 6.01–6.10 (m, 1H), 6.57 (s, 2H), 7.02–7.05 (m, 4H), 7.14–7.17 (m, 1H), 7.35–7.39 (m, 4H). 13C NMR (100 MHz, CDCl3): δ 55.58, 60.52, 60.77, 63.42, 94.26, 118.73, 118.77, 119.58, 123.37, 127.03, 129.44, 130.00, 131.27, 133.29, 134.18, 153.07, 156.09, 157.40, 164.74. HRMS: found 454.1610 (M++Na); C26H25NO5Na requires 454.1630.
4-(4-Benzyloxyphenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7l)
Preparation as described above from crotonyl chloride and (4-benzyloxybenzylidene)-3,4,5-trimethoxyphenylamine (5l) to afford a cream solid, yield 37%, Mp 148–149 °C. IR (KBr) νmax: 1746 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.72 (s, 6H), 3.75–3.76 (m, 1H), 3.78 (s, 3H), 4.74 (d, J = 2.52 Hz, 1H), 5.09 (s, 2H), 5.33–5.42 (m, 2H), 5.99–6.08 (m, 1H), 6.56 (s, 2H), 7.02 (d, J = 8.56 Hz, 2H), 7.31–7.46 (m, 7H). 13C NMR (100 MHz, CDCl3): δ 56.03, 60.97, 61.36, 63.89, 70.08, 94.69, 115.57, 119.92, 127.36, 127.48, 128.14, 128.67, 129.44, 130.58, 133.86, 136.61, 139.50, 153.49, 159.05, 165.37. HRMS: found 468.1774 (M++Na); C27H27NO5Na requires 468.1787.
4-Naphthalen-1-yl-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7m)
Preparation as described above from crotonyl chloride and naphthalen-1-ylmethylene-(3,4,5-trimethoxyphenyl)amine (5m) to afford the product as a yellow solid, yield 34%, Mp 121–122 °C. IR (KBr) νmax: 1754 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.71 (s, 6H), 3.76–3.78 (m, 1H), 3.82 (s, 3H), 5.44–5.49 (m, 2H), 5.60 (d, J = 2.00 Hz, 1H), 6.22–6.31 (m, 1H), 6.67 (s, 2H), 7.44–8.04 (m, 7H). 13C NMR (100 MHz, CDCl3): δ 55.69, 58.42, 60.54, 63.11, 94.49, 120.72, 122.29, 125.10, 125.74, 126.28, 127.86, 128.22, 128.75, 129.96, 130.67, 132.21, 133.45, 133.62, 134.13, 153.19, 164.82. HRMS: found 390.1715 (M++H); C24H24NO4 requires 390.1705.
4-Naphthalen-2-yl-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7n)
Preparation as described above from crotonyl chloride and naphthalen-2-ylmethylene-(3,4,5-trimethoxyphenyl)amine (5n) to afford the product as a yellow solid, yield 30%, Mp 145–146 °C. IR (KBr) νmax: 1749 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.69 (s, 6H), 3.77 (s, 3H), 3.84–3.87 (m, 1H), 4.97 (d, J = 2.52 Hz, 1H), 5.37–5.45 (m, 2H), 6.06–6.12 (m, 1H), 6.62 (s, 2H), 7.47–7.92 (m, 7H). 13C NMR (100 MHz, CDCl3): δ 55.58, 60.50, 61.38, 63.44, 94.25, 119.71, 122.47, 124.97, 126.13, 126.34, 127.39, 127.42, 129.01, 130.00, 132.86, 132.94, 133.45, 134.05, 134.33, 153.08, 164.80. HRMS: found 390.1714 (M++H); C24H24NO4 requires 390.1705.
4-(4-Methoxy-3-nitrophenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7p)
Preparation as described above from crotonyl chloride and (4-methoxy-3-nitrobenzylidene)-(3,4,5-trimethoxyphenyl)amine (5p) to afford a brown oil, yield 14%. IR (NaCl) νmax: 1754 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.75 (s, 6H), 3.78 (s, 3H), 3.85–3.86 (m, 1H), 3.99 (s, 3H), 4.80 (d, J = 2.00 Hz, 1H), 5.37–5.43 (m, 2H), 5.98–6.07 (m, 1H), 6.52 (s, 2H), 7.14–7.16 (m, 1H), 7.54–7.57 (m, 1H), 7.90 (br s, 1H). 13C NMR (100 MHz, CDCl3): δ 55.61, 56.27, 59.66, 60.52, 63.43, 94.23, 114.14, 120.19, 123.18, 129.23, 129.38, 130.74, 132.80, 134.36, 138.76, 152.65, 153.23, 164.19. HRMS: found 437.1326 (M++Na); C21H22N2O7Na requires 437.1325.
4-[4-Oxo-1-(3,4,5-trimethoxyphenyl)-3-vinyl-azetidin-2-yl]benzonitrile (7q)
Preparation as described above from 4-[(3,4,5-trimethoxyphenylimino)methyl]benzonitrile (5q) and trans-crotonyl chloride to afford the product as a colourless oil (31%). IR νmax 1756.1(CO), 2312.0 (CN) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.76 (s, br, 10H), 4.86 (d, J = 2.52 Hz, 1H), 5.40 (m, 2H), 5.90–6.08 (m, 1H), 6.48 (s, 2H), 7.49 (d, 2H), 7.71 (d, 2H). HRMS: Found: 387.1335 (M++Na); C21H20N2O4Na requires 387.1321.
4-(4-Methylsulfanylphenyl)-1-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (7r)
Preparation as described above from crotonyl chloride and
N-(3,4,5-trimethoxybenzylidene)-4-methylsulfanylphenylamine (
5r), yield 17%, brown oil [
98]. IR (NaCl ν max): 1744 (C=O) cm
−1.
1H NMR (400 MHz, CDCl
3): δ 2.48 (s, 3H), 3.72–3.76 (m, 10H, OMe), 4.75 (d,
J = 2.33Hz, 1H), 5.31–5.40 (m, 2H), 5.98–6.05 (m, 1H), 6.54 (s, 2H), 7.25–7.31 (m, 4H).
13C NMR (100 MHz, CDCl
3): δ15.55, 55.88, 55.61, 60.77, 60.47, 63.39, 94.23, 119.59, 125.98, 126.09, 129.96, 133.25, 133.49, 139.00, 141.19, 153.05, 164.70. HRMS: found 408.1230 (M
++Na); C
21H
23NO
4SNa, requires 408.1245.
1-(3,5-Dimethoxyphenyl)-4-(4-methoxyphenyl)-3-vinylazetidin-2-one (7u)
Preparation as described above from imine 5s and crotonyl chloride to afford the product as brown oil; Yield: 17%, IR νmax: 1748.72 cm−1 (C=O, β- lactam). δ 1H NMR (400 MHz, CDCl3): 3.69 (s, 7 H), 3.79 (s, 3 H), 4.68 (s, 1 H), 5.27–5.39 (m, 2 H), 5.94–6.06 (m, 1 H), 6.15 (s, 1 H), 6.48 (s, 2 H), 6.89 (d, J = 7.93 Hz, 2 H), 7.27 (d, J = 8.54 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ 55.31, 55.49, 61.24, 63.97, 95.66, 96.27, 114.58, 119.77, 127.14, 129.16, 130.54, 139.23, 159.79, 161.06, 165.63. HRMS: found 340.1540 (M+ + H); C20H22NO4 requires 340.1549.
4-(3,4,5-Trimethoxyphenyl)-1-(4-fluorophenyl)-3-vinylazetidin-2-one (8a)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)-4-fluorophenylamine (6a) as a yellow oil, yield 18%. IR (NaCl) νmax: 1751 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.77–3.79 (m, 1H), 3.83 (s, 6H), 3.86 (s, 3H), 4.71 (d, J = 2.48 Hz, 1H), 5.35–5.43 (m, 2H), 6.00–6.09 (m, 1H), 6.54 (s, 2H), 6.96–7.00 (m, 2H), 7.29–7.32 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 55.76, 60.43, 61.39, 63.73, 101.99, 115.34, 115.57, 117.98, 118.06, 119.84, 129.87, 132.18, 133.36, 137.63, 153.54, 159.88, 164.74. HRMS: found 358.1454 (M++H); C20H21FNO4 requires 358.1455.
4-(3,4,5-Trimethoxyphenyl)-1-(4-chlorophenyl)-3-vinylazetidin-2-one (8b)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)-4-chlorophenylamine (6b) as a yellow solid, yield 32%, Mp 131–133 °C. IR (KBr) νmax: 1753 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.78–3.79 (m, 1H), 3.83 (s, 6H), 3.87 (s, 3H), 4.71 (d, J = 1.00 Hz, 1H), 5.36–5.43 (m, 2H), 6.02–6.08 (m, 1H), 6.54 (s, 2H), 7.24 (d, J = 5.88 Hz, 2H), 7.28 (d, J = 5.88 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 56.11, 60.70, 61.67, 64.09, 102.43, 118.11, 120.10, 129.04, 130.08, 130.24, 132.33, 135.94, 138.15, 153.91, 165.18. HRMS: found 396.0966 (M++Na); C20H2035ClNO4Na requires 396.0979.
4-(3,4,5-Trimethoxyphenyl)-1-(4-bromophenyl)-3-vinylazetidin-2-one (8c)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxy benzylidene)-4-bromophenylamine (6c) as a colourless solid, yield 32%, Mp 120–122 °C. IR (KBr) νmax: 1754 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.77–3.79 (m, 1H), 3.83 (s, 6H), 3.86 (s, 3H), 4.71 (d, J = 2.48 Hz, 1H), 5.36–5.44 (m, 2H), 6.00–6.07 (m, 1H), 6.53 (s, 2H), 7.22 (d, J = 8.56 Hz, 2H), 7.40 (d, J = 8.52 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 55.79, 60.43, 61.33, 63.82, 101.97, 116.38, 118.16, 119.93, 129.72, 131.67, 132.00, 136.05, 137.70, 153.58, 164.96. HRMS: found 440.0466 (M++Na); C20H2079BrNO4Na requires 440.0473.
4-(3,4,5-Trimethoxyphenyl)-1-(4-nitrophenyl)-3-vinylazetidin-2-one (8d)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)-4-nitrophenylamine (6d) as a yellow oil, yield 42%. IR (NaCl) νmax: 1762 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.85 (s, 6H), 3.87 (s, 3H), 3.89–3.91 (m, 1H), 4.81 (d, J = 2.52 Hz, 1H), 5.40–5.47 (m, 2H), 6.01–6.10 (m, 1H), 6.54 (s, 2H), 7.45 (d, J = 9.04 Hz, 2H), 8.19 (d, J = 9.04 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 55.83, 60.45, 61.77, 64.16, 101.95, 116.45, 120.38, 124.85, 129.10, 131.32, 137.97, 142.11, 143.00, 153.73, 165.55. HRMS: found 383.1234 (M+-H); C20H19N2O6 requires 383.1243.
4-(3,4,5-Trimethoxyphenyl)-1-(4-tert-butylphenyl)-3-vinylazetidin-2-one (8e)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)-4-tert-butylphenylamine (6e) as a yellow solid, yield 22%, Mp 172–174 °C. IR (KBr) νmax: 1746 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 1.29 (s, 9H), 3.76–3.78 (m, 1H), 3.84 (s, 6H), 3.87 (s, 3H), 4.69 (d, J = 2.48 Hz, 1H), 5.33–5.42 (m, 2H), 6.98–6.07 (m, 1H), 6.58 (s, 2H), 7.27 (d, J = 9.04 Hz, 2H), 7.31 (d, J = 9.04 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 30.86, 33.96, 55.78, 60.43, 61.25, 63.56, 102.13, 116.27, 119.58, 125.45, 130.15, 132.77, 134.69, 137.51, 146.63, 153.45, 164.84. HRMS: found 396.2182 (M++H); C24H30NO4 requires 396.2175.
4-(3,4,5-Trimethoxyphenyl)-1-phenyl-3-vinylazetidin-2-one (8f)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)phenylamine (6f) as a colourless solid, yield 34%, Mp 150–151 °C. IR (KBr) νmax: 1752 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.77–3.79 (m, 1H), 3.83 (s, 6H), 3.86 (s, 3H), 4.74 (d, J = 2.48 Hz, 1H), 5.35–5.44 (m, 2H), 6.01–6.10 (m, 1H), 6.56 (s, 2H), 7.07–7.11 (m, 1H), 7.27–7.33 (m, 4H). 13C NMR (100 MHz, CDCl3): δ 55.76, 60.43, 61.19, 63.57, 102.01, 116.60, 119.72, 123.67, 128.65, 130.02, 132.54, 137.12, 137.53, 153.49, 165.02. HRMS: found 362.1371 (M++Na); C20H21NO4Na requires 362.1368.
4-(3,4,5-Trimethoxyphenyl)-1-p-tolyl-3-vinylazetidin-2-one (8g)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)-4-methylphenylamine (6g) as a yellow oil, yield 16%. IR (NaCl) νmax: 1749 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 2.30 (s, 3H), 3.75–3.77 (m, 1H), 3.83 (s, 6H), 3.86 (s, 3H), 4.71 (d, J = 2.48 Hz, 1H), 5.34–5.43 (m, 2H), 6.00–6.09 (m, 1H), 6.55 (s, 2H), 7.09 (d, J = 8.04 Hz, 2H), 7.23 (d, J = 8.56 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 20.48, 55.75, 60.42, 61.16, 63.54, 102.03, 116.54, 119.62, 129.12, 130.15, 132.66, 133.29, 134.69, 137.48, 153.45, 164.76. HRMS: found 376.1534 (M++Na); C21H23NO4Na requires 376.1525.
4-(3,4,5-Trimethoxyphenyl)-1-(4-ethylphenyl)-3-vinylazetidin-2-one (8h)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)-4-ethylphenylamine (6h) as yellow crystals, yield 15%, Mp 110–112 °C. IR (KBr) νmax: 1749 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 1.21 (t, J = 7.48 Hz, 3H), 2.57–2.63 (q, J = 7.52 Hz, 2H), 3.75–3.78 (m, 1H), 3.84 (s, 6H), 3.87 (s, 3H), 4.71 (d, J = 2.52 Hz, 1H), 5.34–5.43 (m, 2H), 6.00–6.09 (m, 1H), 6.57 (s, 2H), 7.12 (d, J = 8.76 Hz, 2H), 7.25–7.29 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 15.62, 28.34, 56.23, 60.89, 61.67, 64.00, 102.54, 117.07, 120.07, 128.42, 130.63, 133.18, 135.37, 137.98, 140.20, 153.93, 165.25. HRMS: found 390.1666 (M++Na). C22H25NO4Na requires 390.1681.
4-(3,4,5-Trimethoxyphenyl)-1-(4-methoxyphenyl)-3-vinylazetidin-2-one (8i)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)-4-methoxyphenylamine (6i) as a yellow oil, yield 18%. IR (NaCl) νmax: 1744 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 3.78 (s, 3H), 3.80–3.82 (m, 1H), 3.83 (s, 6H), 3.86 (s, 3H), 4.69 (d, J = 2.48 Hz, 1H), 5.34–5.43 (m, 2H), 6.03–6.05 (m, 1H), 6.55 (s, 2H), 6.83 (d, J = 9.00 Hz, 2H), 7.28 (d, J = 9.00 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 54.99, 55.75, 60.42, 61.30, 63.59, 102.06, 113.85, 117.92, 119.62, 130.20, 130.68, 132.62, 137.49, 153.46, 155.67, 164.44. HRMS: found 392.1479 (M++Na); C21H23NO5Na requires 392.1474.
N-(4-(2-(3,4,5-Trimethoxyphenyl)-4-oxo-3-vinylazetidin-1-yl)phenyl)acetamide (8j)
Preparation as described above from crotonyl chloride and N-((E)-4-(3,4,5-trimethoxybenzylideneamino)phenyl)acetamide (6j) as a colourless solid, yield 14%, Mp 223–224 °C. IR (KBr) νmax: 1742 (C=O) 1689 (C=O) cm−1. 1H NMR (400 MHz, CDCl3): δ 2.16 (s, 3H), 3.76–3.78 (m, 1H), 3.82 (s, 6H), 3.86 (s, 3H), 4.71 (d, J = 2.52 Hz, 1H), 5.34–5.42 (m, 2H), 6.00–6.09 (m, 1H), 6.54 (s, 2H), 7.27 (d, J = 8.56 Hz, 2H), 7.43 (d, J = 8.56 Hz, 2H), 7.49 (s, 1H). 13C NMR (100 MHz, CDCl3): δ 23.99, 55.75, 60.43, 61.26, 63.63, 102.04, 117.16, 119.80, 120.27, 129.99, 132.36, 133.41, 133.70, 137.52, 153.49, 164.76, 167.92. HRMS: found 419.1579 (M++Na); C22H24N2O5Na requires 419.1583.
1-(4-(Methylthio)phenyl)-4-(3,4,5-trimethoxyphenyl)-3-vinylazetidin-2-one (8k)
Preparation as described above from crotonyl chloride and N-(3,4,5-trimethoxybenzylidene)-4-thiomethylphenylamine (6k) as a colourless solid, yield 41%, Mp 104–106 °C. IR (NaCl, film) νmax: 1748.72 cm−1 (C=O, β-lactam). 1H NMR (400 MHz, CDCl3): δ ppm 2.41 (s, 3 H), 3.73 (d, J = 7.93, 1.22 Hz, 1 H), 3.77–3.85 (m, 9 H), 4.67 (d, J = 2.44 Hz, 1 H), 5.30–5.40 (m, 2 H), 5.98 (d, J = 10.07, 7.63 Hz, 1 H), 6.50 (s, 2 H), 7.13–7.18 (m, 2 H), 7.23 (d, J = 7.32 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ ppm 16.50, 56.21, 60.83, 61.70, 64.07, 102.52, 117.59, 120.12, 127.90, 130.40, 132.77, 133.52, 135.16, 153.95, 165.19. HRMS: found 408.1255 (M++Na); C21H23NNaO4S requires 408.1246.