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Synlett 2007(15): 2420-2424  
DOI: 10.1055/s-2007-985607
LETTER
© Georg Thieme Verlag Stuttgart · New York

Microwave-Assisted Solvent-Free Synthesis of Enol Carbamates

Julio A. Seijas*, M. Pilar Vázquez-Tato*, José Crecente-Campo
Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Santiago de Compostela, Aptdo 280, 27080 Lugo, Spain
Fax: +34(982)285872; e-Mail: qoseijas@lugo.usc.es; e-Mail: pilarvt@lugo.usc.es;
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Publication History

Received 20 June 2007
Publication Date:
23 August 2007 (online)

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Abstract

An efficient and simple method for the synthesis of enol carbamates by irradiation with microwaves under solvent-free ­conditions has been developed. The method has been applied to substituted acetophenones, cyclic aryl ketones and α-aryl ketones. Its main advantages are short reaction times, good conversions ­except for nitro acetophenones, and the environmentally friendly nature of the process. For α-aryl ketones the reaction shows regio­selectivity to afford conjugated products.

Key words

solvent-free - microwave - enol carbamates

19

It has been described that 1-phenylvinyl N,N-diisopropyl-carbamate was obtained in 73% yield; however, we have never been able to get yields higher than 50%, even with longer reaction times or higher temperatures.

32

Longer reaction times did not improve the yield significantly.

34

General Procedure for the Synthesis of 1-Arylalkenyl N , N- Diisopropylcarbamates 2; Synthesis of 1-Phenyl-vinyl N , N -Diisopropylcarbamate (2a): A stirred mixture of acetophenone (1a) (120 mg, 1 mmol), N,N-diisopropyl-carbamoyl chloride (163 mg, 1.5 mmol) and 2,4,6-collidine (121 mg, 1.5 mmol) was irradiated in an open vessel with microwaves in a monomode oven (Discover CEM, 50 W and temperature control set at 150 °C measured with an IR sensor) for 60 min. The crude was dissolved in CH2Cl2 (30 mL) and washed with 10% aq HCl (2 × 20 mL), dried (Na2SO4) and evaporated to give 1-phenylvinyl N,N-diiso-propylcarbamate (2a). Further purification by distillation (160 °C, 1 mm Hg) gave 155 mg (63%) of 2a; mp 61-63 °C (hexane), lit.13 mp 60-62 °C.

35

Enol carbamates and parent ketones show very similar R f values, making it very difficult to separate them by chromatography. When purification by distillation is not possible, a very easy way to remove the starting material is to reduce it to the corresponding alcohol with sodium borohydride followed by column chromatography. This very method must also have been used in previously described literature procedures as we confirmed in our laboratory.

36

Data of previously undescribed compounds:
1-(4-Methoxyphenyl)vinyl N , N -Diisopropylcarbamate (2b): Oil. 1H NMR (300 MHz, CDCl3): δ = 1.28-1.32 [m, 12 H, 2 × CH(CH 3)2], 3.80 (s, 3 H, OMe), 3.99-4.03 [m, 2 H, 2 × CH(CH3)2], 4.87 (d, J = 1.8 Hz, 1 H, C=CH2), 5.28 (d, J = 1.8 Hz, 1 H, C=CH2), 6.87 (d, J = 8.8 Hz, 2 H, ArH), 7.41 (d, J = 8.8 Hz, 2 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.8, 46.4, 46.8, 55.5, 99.7, 114.0, 126.5, 128.4, 153.5, 153.7, 160.1. MS (EI): m/z (%) = 278 (9) [M+ + 1], 277 (22) [M+], 135 (45), 128 (100). IR (KBr, film): 1713, 1512, 1252, 1041, 837 cm-1. Anal. Calcd for C16H23NO3: C, 69.29; H, 8.36; N, 5.05. Found: C, 68.95; H, 8.76; N, 4.72.
1-(4-Benzyloxyphenyl)vinyl N , N -Diisopropylcarbamate (2c): mp 94-95 °C (hexane). 1H NMR (300 MHz, CDCl3): δ = 1.24-1.33 [m, 12 H, 2 × CH(CH 3)2], 4.02 [br s, 2 H, 2 × CH(CH3)2], 4.90 (d, J = 1.8 Hz, 1 H, C=CH2), 5.07 (s, 2 H, OCH 2Ph), 5.30 (d, J = 1.8 Hz, 1 H, C=CH2), 6.93 (d, J = 8.8 Hz, 2 H, ArH), 7.32-7.42 (m, 7 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 20.8, 46.4, 46.9, 70.3, 99.8, 115.0, 126.6, 127.7, 128.2, 128.6, 128.8, 137.1, 153.5, 153.7, 159.4. MS (EI): m/z (%) = 353 (50) [M+], 128 (100). IR (KBr, film): 1705, 1246, 1215, 1011, 841 cm-1. Anal. Calcd for C22H27NO3: C, 74.76; H, 7.70; N, 3.96. Found: C, 75.12; H, 8.07; N, 3.91.
1-(4-Isopropoxyphenyl)vinyl N , N -Diisopropylcarbamate (2d): Oil. 1H NMR (300 MHz, CDCl3): δ = 1.29-1.33 [m, 18 H, 3 × CH(CH 3)2], 4.01 [sept, J = 6.8 Hz, 2 H, 2 × CH(CH3)2], 4.54 [sept, J = 6.0 Hz, 1 H, CH(CH3)2], 4.86 (d, J = 2.2 Hz, 1 H, C=CH2), 5.27 (d, J = 1.8 Hz, 1 H, C=CH2), 6.8 (d, J = 8.8 Hz, 2 H, ArH), 7.39 (d, J = 8.8 Hz, 2 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.8, 22.2, 46.3, 46.8, 70.1, 99.5, 115.7, 115.9, 126.5, 153.6, 153.7, 158.5. MS (EI): m/z (%) = 305 (8) [M+], 128 (100), 86 (36). IR (KBr, film): 2975, 1712, 1509, 1248 cm-1. Anal. Calcd for C18H27NO3: C, 70.79; H, 8.91; N, 4.59. Found: C, 71.07; H, 8.94; N, 4.76.
1-(4-{[(Diisopropylamino)carbonyl]oxy}phenyl)vinyl N , N -Diisopropylcarbamate (2e): mp 59-61 °C. 1H NMR (300 MHz, CDCl3): δ = 1.30 [m, 24 H, 4 × CH(CH 3)2], 4.00 [hept, J = 6.6 Hz, 4 H, 4 × CH(CH3)2], 4.95 (d, J = 2.2 Hz, 1 H, CH=CH 2), 5.33 (d, J = 2.2 Hz, 1 H, CH=CH 2), 7.10 (d, J = 8.8 Hz, 2 H, ArH), 7.46 (d, J = 8.8 Hz, 2 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.6, 21.8, 46.4, 46.8, 101.2, 121.9, 126.2, 132.6, 151.9, 153.2, 153.5, 153.8. MS (EI): m/z (%) = 390 (4) [M+], 128 (100), 86 (44). IR (KBr, film): 1715, 1315, 1258, 1214, 1154 cm-1. Anal. Calcd for C22H34N2O4: C, 67.66; H, 8.78; N, 7.17. Found: C, 67.36; H, 8.89; N, 7.05.
1-(4-Fluorophenyl)vinyl N , N -Diisopropylcarbamate (2f): Oil. 1H NMR (300 MHz, CDCl3): δ = 1.25-1.33 [m, 12 H, 2 × CH(CH 3)2], 4.00 [sept, J = 6.6 Hz, 2 H, 2 × CH(CH3)2], 4.96 (d, J = 2.2 Hz, 1 H, C=CH 2), 5.33 (d, J = 2.2 Hz, 1 H, C=CH 2), 7.02 (t, J = 8.8 Hz, 2 H, ArH), 7.44 (dd, J = 5.3, 9.0 Hz, 2 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.8, 47.0, 101.4, 115.6 (d, 2 J CF = 22 Hz), 127.0, 131.9, 152.9, 153.5, 163.1 (d, 1 J CF = 248 Hz). MS (EI): m/z (%) = 265 (5) [M+], 128 (68), 86 (100). IR (KBr, film): 2968, 1712, 1510, 1259, 1214, 1043 cm-1. Anal. Calcd for C15H20FNO2: C, 67.90; H, 7.60; N, 5.28. Found: C, 68.07; H, 7.47; N, 5.19.
1-(4-Nitrophenyl)vinyl N , N -Diisopropylcarbamate (2g): mp 83-86 °C. 1H NMR (300 MHz, CDCl3): δ = 1.26-1.35 [m, 12 H, 2 × CH(CH 3)2], 4.01 [sept, J = 6.6 Hz, 2 H, 2 × CH(CH3)2], 5.19 (d, J = 2.2 Hz, 1 H, C=CH2), 5.56 (d, J = 2.2 Hz, 1 H, C=CH2), 7.60 (d, J = 9.2 Hz, 2 H, ArH), 8.20 (d, J = 8.8 Hz, 2 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.6, 21.8, 46.6, 47.1, 105.5, 124.1, 125.9, 142.0, 147.9, 151.9, 153.1. MS (EI): m/z (%) = 292 (1) [M+], 165 (28), 128 (94), 86 (100). IR (KBr, film): 2971, 1709, 1519, 1345, 1262 cm-1. Anal. Calcd for C15H20N2O4: C, 61.63; H, 6.90; N, 9.58. Found: C, 61.34; H, 6.41; N, 9.62.
1-(3-Benzyloxyphenyl)vinyl Diisopropylcarbamate (2h): Oil. 1H NMR (300 MHz, CDCl3): δ = 1.29-1.34 [m, 12 H, 2 × CH(CH 3)2], 4.03 [sept, J = 6.8 Hz, 2 H, 2 × CH(CH3)2], 5.00 (d, J = 1.8 Hz, 1 H, C=CH 2), 5.07 (s, 2 H, OCH 2Ph), 5.40 (d, J = 1.8 Hz, 1 H, C=CH 2), 6.93 (br d, J = 7.9 Hz, 1 H, ArH), 7.10 (m, 2 H, ArH), 7.26 (t, J = 7.9 Hz, 1 H, ArH), 7.30-7.45 (m, 5 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.8, 46.5, 46.9, 70.3, 101.9, 111.8, 115.5, 118.0, 127.7, 128.2, 128.8, 129.7, 137.1, 137.2, 153.5, 159.1. MS (EI): m/z (%) = 353 (2) [M+], 128 (100), 91 (30). IR (KBr, film): 2969, 1712, 1431, 1264, 1042 cm-1. Anal. Calcd for C22H27NO3: C, 74.76; H, 7.70; N, 3.96. Found: C, 74.38; H, 7.24; N, 3.38.
1-(3-{[(Diisopropylamino)carbonyl]oxy}phenyl)vinyl N , N -Diisopropylcarbamate (2i): mp 74-77 °C. 1H NMR (300 MHz, CDCl3): δ = 1.29 [m, 24 H, 4 × CH(CH 3)2], 4.00 [br s, 4 H, 4 × CH(CH3)2], 5.00 (d, J = 1.8 Hz, 1 H, CH=CH 2), 5.41 (d, J = 2.2 Hz, 1 H, CH=CH 2), 7.08 (dt, J = 2.2, 7.0 Hz, 1 H, ArH), 7.20 (m, 1 H, ArH), 7.28-7.34 (m, 2 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.7, 46.6, 102.2, 118.7, 121.7, 122.3, 129.4, 137.1, 151.7, 153.0. MS (EI): m/z (%) = 390 (18) [M+], 128 (100). IR (KBr, film): 1712, 1427, 1257, 1198, 1153 cm-1. Anal. Calcd for C22H34N2O4: C, 67.66; H, 8.78; N, 7.17. Found: C, 67.57; H, 8.42; N, 7.68.
1-(3-Nitrophenyl)vinyl N , N -Diisopropylcarbamate (2j): mp 85-89 °C. 1H NMR (300 MHz, CDCl3): δ = 1.27-1.39 [m, 12 H, 2 × CH(CH 3)2], 4.02 [br s, 2 H, 2 × CH(CH3)2], 5.17 (d, J = 2.6 Hz, 1 H, C=CH2), 5.54 (d, J = 2.2 Hz, 1 H, C=CH2), 7.52 (t, J = 8.1 Hz, 1 H, ArH), 7.81 (ddd, J = 0.8, 1.7, 7.9 Hz, 1 H, ArH), 8.16 (ddd, J = 1.4, 2.2, 8.2 Hz, 1 H, ArH), 8.30 (t, J = 2.0 Hz, 1 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.6, 21.7, 46.7, 47.1, 104.1, 120.0, 123.4, 129.7, 130.9, 137.6, 148.7, 151.6, 153.1. MS (EI): m/z (%) = 292 (2) [M+], 165 (40), 128 (100), 86 (32). IR (KBr, film): 2975, 1713, 1532, 1350, 1255, 1042 cm-1. Anal. Calcd for C15H20N2O4: C, 61.63; H, 6.90; N, 9.58. Found: C, 61.36; H, 7.15; N, 9.34.
1-(2-Benzyloxyphenyl)vinyl N , N -Diisopropylcarbamate (2k): mp 38-40 °C. 1H NMR (300 MHz, CDCl3): δ = 1.25 [d, J = 6.6 Hz, 12 H, 2 × CH(CH 3)2], 3.97 [sept, J = 6.6 Hz, 2 H, 2 × CH(CH3)2], 5.16 (m, 3 H, C=CH 2, OCH 2Ph), 5.60 (d, J = 0.9 Hz, 1 H, C=CH 2), 6.93-6.98 (m, 2 H, ArH), 7.20-7.46 (m, 7 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.7, 46.3, 46.7, 70.7, 106.5, 113.2, 121.0, 125.2, 127.5, 128.0, 128.7, 129.6, 137.2, 150.5, 153.8, 156.4. MS (EI): m/z (%) = 353 (40) [M+], 128 (100) [Cb], 91 (23). IR (KBr, film): 2969, 1710 (C=O), 1446, 1289, 1240 (CO), 1043, 754 cm-1. Anal. Calcd for C22H27NO3: C, 74.76; H, 7.70; N, 3.96. Found: C, 74.76; H, 7.43; N, 3.87.
1-(2-{[(Diisopropylamino)carbonyl]oxy}phenyl)vinyl N , N -Diisopropylcarbamate (2l): Oil. 1H NMR (300 MHz, CDCl3): δ = 1.23-1.32 [m, 24 H, 4 × CH(CH 3)2], 3.91 [br s, 3 H, 3 × CH(CH3)2], 4.18 [br s, 1 H, CH(CH3)2], 5.15 (s, 1 H, C=CH 2), 5.18 (s, 1 H, CH=CH 2), 7.09 (d, J = 7.9 Hz, 1 H, ArH), 7.16 (t, J = 7.5 Hz, 1 H, ArH), 7.29 (t, J = 7.7 Hz, 1 H, ArH), 7.42 (d, J = 7.9 Hz, 1 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.7, 46.7, 46.9, 105.4, 123.6, 125.1, 129.3, 129.4, 129.6, 149.0, 149.8, 153.4, 153.5. MS (EI): m/z (%) = 391 (5) [M+ + 1], 390 (1) [M+], 128 (100), 86 (81). IR (KBr, film): 2970, 1715, 1316, 1207, 1042 cm-1. Anal. Calcd for C22H34N2O4: C, 67.66; H, 8.78; N, 7.17. Found: C, 67.22; H, 9.21; N, 6.95.
1-(3,4-Dimethoxyphenyl)vinyl N , N -Diisopropyl-carbamate (2m): Oil. 1H NMR (300 MHz, CDCl3): δ = 1.26-1.32 [m, 12 H, 2 × CH(CH 3)2], 3.86 (s, 6 H, 2 × OMe), 4.01 [sept, J = 6.6 Hz, 2 H, 2 × CH(CH3)2], 4.89 (d, J = 1.8 Hz, 1 H, C=CH2), 5.28 (d, J = 1.8 Hz, 1 H, C=CH2), 6.81 (d, J = 8.4 Hz, 1 H, ArH), 6.98 (d, J = 1.8 Hz, 1 H, ArH), 7.04 (dd, J = 2.2, 8.3 Hz, 1 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.8, 46.4, 46.8, 55.9, 56.1, 100.0, 108.4, 111.2, 118.0, 128.6, 148.9, 149.7, 153.4, 153.5. MS (EI): m/z (%) = 307 (7) [M+], 180 (13), 128 (100), 86 (65). IR (KBr, film): 1712, 1516, 1265, 1221, 1143 cm-1. Anal. Calcd for C17H25NO4: C, 66.43; H, 8.20; N, 4.56. Found: C, 66.41; H, 7.79; N, 4.63.
1-(4-Benzyloxy-3-methoxyphenyl)vinyl N , N -Diiso-propylcarbamate (2n): mp 75-77 °C. 1H NMR (300 MHz, CDCl3): δ = 1.26-1.33 [m, 12 H, 2 × CH(CH 3)2], 3.89 (s, 3 H, OMe), 4.02 [m, 2 H, 2 × CH(CH3)2], 4.90 (d, J = 1.8 Hz, 1 H, C=CH 2), 5.16 (s, 2 H, OCH 2Ph), 5.30 (d, J = 2.2 Hz, 1 H, C=CH2), 6.84 (d, J = 8.4 Hz, 1 H, ArH), 6.98-7.03 (m, 2 H, ArH), 7.25-7.44 (m, 5 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.8, 21.8, 46.4, 46.9, 56.1, 71.2, 100.2, 109.0, 113.9, 117.9, 127.4, 128.1, 128.8, 129.1, 137.2, 148.9, 149.6, 153.4, 153.6. MS (EI): m/z (%) = 383 (5) [M+], 128 (100), 91 (94), 86 (66). IR (KBr, film): 1712, 1520, 1272, 1222, 1147, 1020 cm-1. Anal. Calcd for C23H29NO4: C, 72.04; H, 7.62; N, 3.65. Found: C, 71.95; H, 7.93; N, 3.60.
1-(4-{[(Diisopropylamino)carbonyl]oxy}-3-methoxy-phenyl)vinyl N , N -Diisopropylcarbamate (2o): Oil. 1H NMR (300 MHz, CDCl3): δ = 1.30 [m, 24 H, 4 × CH(CH 3)2], 3.80 (s, 3 H, OMe), 4.00 [sept, J = 6.4 Hz, 4 H, 4 × CH(CH3)2], 4.96 (s, 1 H, CH=CH 2), 5.32 (s, 1 H, CH=CH 2), 7.03-7.05 (m, 3 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.3, 20.7, 21.6, 46.8, 56.0, 101.3, 109.6, 117.8, 123.4, 133.8, 135.3, 141.3, 151.7, 153.3. MS (EI): m/z (%) = 420 (2) [M+], 293 (1), 128 (100), 86 (44). IR (KBr, film): 1716, 1316, 1281, 1267, 1204, 1154, 1126 cm-1. Anal. Calcd for C23H36N2O5: C, 65.69; H, 8.63; N, 6.66. Found: C, 65.63; H, 8.74; N, 6.54.
1-(2-Naphthyl)vinyl N , N -Diisopropylcarbamate (2p): mp 58-59 °C. 1H NMR (300 MHz, CDCl3): δ = 1.26-1.40 [m, 12 H, 2 × CH(CH 3)2], 4.07 [m, 2 H, 2 × CH(CH3)2], 5.09 (d, J = 2.0 Hz, 1 H, C=CH2), 5.55 (d, J = 2.0 Hz, 1 H, C=CH2), 7.44-7.48 (m, 2 H, ArH), 7.63 (dd, J = 1.8, 8.8 Hz, 1 H, ArH), 7.79-7.82 (m, 3 H, ArH), 7.90 (d, J = 1.7 Hz, 1 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.8, 46.5, 46.9, 102.1, 123.2, 124.3, 126.5, 126.6, 127.8, 128.4, 128.7, 133.0, 133.4, 133.6, 153.6, 153.7. MS (EI): m/z (%) = 298 (11) [M+ + 1], 297 (42) [M+], 170 (39), 128 (90), 86 (100). IR (KBr, film): 2968, 1707 (C=O), 1645, 1429, 1323, 1265, 1041, 864, 760 cm-1. Anal. Calcd for C19H23NO2: C, 76.73; H, 7.80; N, 4.71. Found: C, 77.11; H, 7.47; N, 5.13.
1 H -Inden-3-yl N , N -Diisopropylcarbamate (2q):33 Oil. 1H NMR (300 MHz, CDCl3): δ = 1.31 [d, J = 7.0 Hz, 12 H, 2 × CH(CH 3)2], 3.62 (s, 2 H, CH2), 3.90 [br s, 1 H, CH(CH3)2], 4.11 [br s, 1 H, CH(CH3)2], 6.53 (s, 1 H, CHCH2), 7.12 (td, J = 1.8, 7.0 Hz, 1 H, ArH), 7.20-7.29 (m, 2 H, ArH), 7.32 (d, J = 7.2, 1 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.8, 38.3, 46.4, 47.1, 113.3, 120.7, 123.5, 124.0, 126.8, 137.6, 143.7, 152.8, 156.8. MS (EI): m/z (%) = 260 (2) [M+ + 1], 132 (54), 128 (84), 86 (100). IR (KBr, film): 2970, 1711, 1606, 1272, 1132, 748, 715 cm-1.
2 H -Chromen-4-yl N , N-Diisopropylcarbamate (2s): mp 74.1-77.4 °C (hexane). 1H NMR (300 MHz, CDCl3): δ = 1.30-1.32 [m, 12 H, 2 × CH(CH 3)2], 4.02 [sept, J = 6.8 Hz, 2 H, 2 × CH(CH3)2], 4.96 (d, J = 3.5 Hz, 2 H, CH2O), 5.49 (t, J = 3.7 Hz, 1 H, C=CHCH2), 6.79 (dd, J = 0.9, 8.0 Hz, 1 H, ArH), 6.87 (td, J = 0.9, 7.5 Hz, 1 H, ArH), 7.06 (dd, J = 1.6, 7.7 Hz, 1 H, ArH), 7.13 (td, J = 1.6, 7.9 Hz, 1 H, ArH). 13C NMR (75 MHz, CDCl3): δ = 20.7, 21.7, 46.7, 47.0, 65.7, 108.0, 116.1, 120.5, 121.3, 121.9, 130.0, 143.4, 152.9, 155.4. MS (EI): m/z (%) = 276 (4) [M+ + 1], 275 (19) [M+], 147 (69), 128 (83), 86 (100). IR (KBr, film): 2970, 1716 (C=O), 1306, 1207, 755 cm-1. Anal. Calcd for C16H21NO3: C, 69.79; H, 7.69; N, 5.09. Found: C, 69.89; H, 8.05; N, 5.06.
1-(4-Methoxyphenyl)prop-1-en-2-yl N , N -Diisopropyl-carbamate (2t); mixture of E- and Z-isomers (2:1): oil. 1H NMR (300 MHz, CDCl3): δ = 1.22-1.26 [m, 12 H, 2 × CH(CH 3)2], 2.04 (d, J = 0.9 Hz, 3 H, Me, E-isomer), 2.09 (d, J = 0.9 Hz, 3 H, Me, Z-isomer), 3.73 (s, 3 H, OMe, E-isomer), 3.75 (s, 3 H, OMe, Z-isomer), 3.85-4.00 [m, 2 H, 2 × CH(CH3)2], 5.83 (s, 1 H, C=CH, E-isomer), 6.19 (s, 1 H, C=CH, Z-isomer), 6.77 (d, J = 8.8 Hz, 2 H, ArH, E-isomer), 6.83 (d, J = 8.8 Hz, 2 H, ArH, Z-isomer), 7.18 (d, J = 8.4 Hz, 2 H, ArH, Z-isomer), 7.26 (d, J = 8.8 Hz, 2 H, ArH, E-isomer). 13C NMR (75 MHz, CDCl3): δ = 17.7, 20.8, 21.1, 21.7, 46.6, 55.3, 113.7, 113.9, 115.7, 117.7, 127.9, 128.2, 129.5, 130.1, 145.2, 147.2, 152.7, 154.1, 158.5. MS (EI): m/z (%) = 292 (6) [M+ + 1], 291 (16) [M+], 164 (27), 163 (23), 135 (29), 128 (90), 121 (43), 86 (100). IR (KBr, film): 2970, 1707, 1512, 1252, 1041, 837, 757 cm-1. Anal. Calcd for C17H25NO3: C, 70.07; H, 8.65; N, 4.81. Found: C, 70.55; H, 8.74; N, 4.79.