Alkenes for Cycloaddition–Retroelectrocyclization Reactions
464 (6630), 327 nm (13500 m–1 cm–1). HRMS (MALDI, 3-HPA):
(2 C, NMe2), 61.56 (1 C, CO2CH2CH3), 62.08 and 62.21 (2 C, 2
m/z (%) = 390.1424 (73) [M + Na]+, 368.1605 (100) [M + H]+, CO2CH2CH3), 99.41 (1 C, C-3), 111.01 (2 C, C-3Ј,5Ј), 117.64 (1 C,
367.1527 (62) [M]+ (calcd. for C20H21N3O4 367.1527).
CN), 121.46 (1 C, C-1Ј), 131.50 (1 C, C-5Ј), 132.50 (2 C, C-2Ј,6Ј),
144.31 (1 C, C-1), 152.94 (1 C, C-4Ј), 162.91 and 162.95 (2 C, 2
CO2CH2CH3), 163.25 (1 C, C-2), 163.92 (1 C, CO2CH2CH3) ppm.
Data for (E,Z)-18: Rf = 0.25 (SiO2; EtOAc/cyclohexane, 3:7); m.p.
1
107–111 °C. H NMR (400 MHz, CDCl3): δ = 1.16 (t, J = 7.1 Hz,
IR (ATR): ν = 2989 (w), 2211 (w), 1717 (m), 1703 (m), 1631 (w),
˜
3 H, CO2CH2CH3), 1.36 (t, J = 7.1 Hz, 3 H, CO2CH2CH3), 3.07
(s, 6 H, NMe2), 4.06 (q, J = 7.1 Hz, 2 H, CO2CH2CH3), 4.30 (q, J
= 7.1 Hz, 2 H, CO2CH2CH3), 6.66 (d, J = 9.2 Hz, 2 H, 2,6-H),
7.59 (d, J = 9.2 Hz, 2 H, 3,5-H), 8.08 (s, 1 H, 4-H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 13.95 (1 C, CO2CH2CH3), 14.29 (1 C,
CO2CH2CH3), 40.11 (2 C, NMe2), 62.57 (1 C, CH3CH2O-C1),
62.79 (1 C, C CH3CH2O-C6), 97.68 (1 C, C-2), 109.75 (1 C, CN),
111.32 (2 C, C-3Ј,5Ј), 115.32 (1 C, C-1Ј), 117.13 (1 C, CN), 120.54
(1 C, C-1Ј), 131.78 (2 C, C-2Ј,6Ј), 153.07 (1 C, C-4Ј), 157.08 (1 C,
C-2), 159.92 (1 C, CO2CH2CH3), 161.43 (1 C, CO2CH2CH3),
1602 (m), 1542 (w), 1508 (m), 1464 (w), 1441 (w), 1377 (w), 1365
(w), 1322 (w), 1243 (s), 1207 (s), 1135 (m), 1106 (m), 1096 (m),
1066 (m), 1021 (m), 943 (w), 890 (w), 860 (w), 835 (w), 820 (w),
797 (w), 764 (s), 749 (s), 709 (w), 670 (w), 643 (w), 620 (w) cm–1.
UV/Vis (CHCl3): λmax (ε) = 449 (17500), 298 nm (19700 m–1 cm–1).
HRMS (MALDI, 3-HPA): m/z (%) = 437.1683 (100) [M + Na]+,
415.1868 (23) [M + H]+, 414.1788 (60) [M]+ (calcd. for C22H26N2O6
414.1785).
Data for Compound 22: Rf = 0.15 (SiO2; EtOAc/cyclohexane, 3:7);
m.p. 143–145 °C. 1H NMR (400 MHz, CDCl3): δ = 1.20 (t, J =
7.1 Hz, 3 H, OCH2CH3), 1.32 (t, J = 7.1 Hz, 3 H, CO2CH2CH3),
1.39 (t, J = 7.1 Hz, 3 H, CO2CH2CH3), 3.10 (s, 6 H, NMe2), 4.08
(q, J = 7.1 Hz, 2 H, OCH2CH3), 4.33 (m, 4 H, CO2CH2CH3), 6.65
(d, J = 9.2 Hz, 2 H, 3Ј,5Ј-H), 7.88 (d, J = 9.2 Hz, 2 H, 2Ј,6Ј-H),
8.10 (s, 1 H, 4-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 14.21
and 14.24 (2 C, CO2CH2CH3), 14.89 (1 C, OCH2CH3), 40.19 (2 C,
NMe2), 61.29 and 62.60 (2 C, CO2CH2CH3), 67.95 (1 C,
OCH2CH3), 86.32 (1 C, C-1), 111.07 (2 C, C-3Ј,5Ј), 114.74 (1 C,
CN), 124.27 (1 C, C-1Ј), 131.66 (2 C, C-2Ј,6Ј), 133.77 (1 C, C-3),
136.69 (1 C, C-2), 154.40 (1 C, C-4Ј), 162.96 and 163.54 (1 C, 2
CO2CH2CH3), 178.56 (1 C, C-4), 185.37 (1 C, C-5) ppm. IR
163.27 (1 C, C-3) ppm. IR (ATR): ν = 2984 (w), 2216 (w), 1732
˜
(m), 1708 (m), 1603 (s), 1514 (s), 1443 (w), 1368 (m), 1326 (m),
1255 (s), 1226 (s), 1204 (s), 1172 (w), 1109 (s), 1018 (w), 946 (w),
852 (w), 822 (w), 778 (w), 748 (w), 711 (w) cm–1. UV/Vis (CHCl3):
λmax (ε) = 448 (17100) 343 nm (7600 m–1 cm–1). HRMS (MALDI,
3-HPA): m/z (%) = 390.1424 (70) [M + Na]+, 368.1605 (100) [M +
H]+, 367.1527 (62) [M]+ (calcd. for C20H21N3O4 367.1527).
Synthesis of Compounds 20–22 Starting from Triester 19: A solution
of alkyne 2 (50 mg, 0.34 mmol) in MeCN (3.4 mL) was treated with
alkene 19 (60 mg, 0.34 mmol) and the mixture was stirred for 5 h
at reflux. Evaporation and flash column chromatography (SiO2;
EtOAc/cyclohexane, 1:4) afforded two fractions, A and B. Evapora-
tion of fraction A gave a red solid that was dissolved in warm
cyclohexane and the solid that formed was collected to give 20
(29 mg, 21%) as a yellow solid. The filtrate was concentrated under
reduced pressure to afford compound 21 (87 mg, 63%) as a red
solid. Evaporation of fraction B yielded compound 22 (6 mg, 4%)
as yellow crystals.
(ATR): ν = 2986 (w), 2217 (w), 1722 (s), 1651 (w), 1616 (w), 1562
˜
(s), 1541 (m), 1480 (w), 1441 (w), 1416 (w), 1396 (w), 1378 (m),
1318 (w), 1275 (s), 1260 (s), 1195 (m), 1169 (m), 1128 (m), 1105 (s),
1088 (s), 1034 (m), 1012 (m), 941 (w), 917 (w), 895 (w), 882 (w),
855 (w), 833 (m), 800 (w), 764 (s), 749 (s), 711 (w), 680 (w), 631
(w), 610 (w) cm–1. UV/Vis (CHCl3): λmax (ε) = 423 (13200), 271 nm
(20700 m–1 cm–1). HRMS (MALDI, 3-HPA): m/z (%) = 437.1683
(100) [M + Na]+, 415.1865 (13) [M + H]+ (calcd. for C22H27N2O6
415.1864).
Data for 20: Rf = 0.30 (SiO2; EtOAc/cyclohexane, 3:7); m.p. 154–
1
155 °C. H NMR (400 MHz, CDCl3): δ = 1.32 (t, J = 7.1 Hz, 6 H,
2 CO2CH2CH3), 1.45 (t, J = 7.1 Hz, 3 H, CO2CH2CH3), 3.00 (s, 6
H, NMe2), 4.29 and 4.30 (q, J = 7.1 Hz, 4 H, CO2CH2CH3), 4.42
(q, J = 7.1 Hz, 2 H, CO2CH2CH3), 5.58 (s, 1 H, 5-H), 6.68 (d, J =
9.0 Hz, 2 H, 3Ј,5Ј-H), 7.41 (d, J = 9.0 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 14.16 (2 C, 2 CO2CH2CH3), 14.97
(1 C, CO2CH2CH3), 40.32 (2 C, NMe2), 54.75 (1 C, C-4), 61.79 (1
C, CO2CH2CH3), 62.75 (2 C, 2 CO2CH2CH3), 65.85 (1 C,
CO2CH2CH3), 93.36 (1 C, C-5), 111.78 (2 C, C-3Ј,5Ј), 116.52 (1 C,
CN), 118.55 (1 C, C-1Ј), 126.14 (2 C, C-2Ј,6Ј), 148.67 (1 C, C-6),
Synthesis of Compounds 37–39 Starting from Tetraester 36: A solu-
tion of alkyne 2 (63 mg, 0.43 mmol) in (CH2Cl)2 (4.3 mL) was
treated with alkene 36 (146 mg, 0.43 mmol) and the mixture was
stirred for 36 h at reflux. Evaporation and flash column chromatog-
raphy (SiO2; EtOAc/cyclohexane, 1:4) afforded two fractions, A
and B. Evaporation of fraction B afforded compound 39 (33 mg,
16%) as a red sticky oil. Fraction A [Rf = 0.44 (SiO2; EtOAc/cyclo-
hexane, 3:7)] was re-subjected to flash column chromatography
(SiO2; EtOAc/CH2Cl2, 1:9), which give two fractions, C and D.
Evaporation of fraction C delivered 38 (80 mg, 38%) as a red sticky
oil. Evaporation of fraction D afforded 37 (24 mg, 11%) as a yellow
solid.
151.49 (1 C, C-4Ј), 163.53 (1 C, C-2), 168.81 (2 C,
2
CO CH CH ) ppm. IR (ATR): ν = 2982 (w), 2906 (w), 2211 (m),
˜
2
2
3
1754 (m), 1725 (s), 1686 (s), 1608 (s), 1530 (m), 1474 (w), 1443 (w),
1401 (w), 1374 (m), 1341 (w), 1322 (w), 1285 (m), 1251 (s), 1198
(s), 1160 (m), 1122 (w), 1074 (w), 1028 (s), 982 (w), 950 (w), 890
(w), 865 (w), 851 (w), 812 (s), 758 (w), 727 (w), 716 (w), 683 (w),
653 (w), 639 (w), 623 (w) cm–1. UV/Vis (CHCl3): λmax (ε) = 319 nm
(22500 m–1 cm–1). HRMS (MALDI, 3-HPA): m/z (%) = 437.1682
(100) [M + Na]+, 415.1864 (33) [M + H]+ (calcd. for C22H27N2O6
415.1864).
Data for 37: Rf = 0.41 (SiO2; EtOAc/CH2Cl2, 1:9); m.p. 98–102 °C.
1H NMR (400 MHz, CDCl3): δ = 1.30 (t, J = 7.1 Hz, 6 H, 2
CO2CH2CH3), 3.01 (s, 6 H, NMe2), 4.26 (q, J = 7.1 Hz, 4 H, 2
CO2CH2CH3), 4.78 (s, 2 H, OCH2CN), 4.96 (s, 2 H, 2-OCH2CN),
5.65 (s, 1 H, 5-H), 6.70 (d, J = 9.0 Hz, 2 H, 3Ј,5Ј-H), 7.45 (d, J =
9.0 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 14.13
Data for Compound 21: Rf = 0.30 (SiO2; EtOAc/cyclohexane, 3:7); (2 C, 2 CO2CH2CH3), 40.29 [2 C, N(CH3)2], 48.42 (1 C, OCH2CN),
1
m.p. 85 °C. H NMR (400 MHz, CDCl3): δ = 1.05 (t, J = 7.1 Hz,
3 H, CO2CH2CH3), 1.31 and 1.34 (t, J = 7.1 Hz, 6 H, 2
53.01 (1 C, 2-OCH2CN), 55.84 (1 C, C-4), 62.66 (2 C, 2
CO2CH2CH3), 83.38 (1 C, C-3), 95.39 (1 C, C-5), 111.88 (2 C, C-
CO2CH2CH3), 3.04 (s, 6 H, NMe2), 3.79 (q, J = 7.1 Hz, 2 H, 3Ј,5Ј), 114.20 and 114.59 (2 C, 2 CN), 117.90 (1 C, C-1Ј), 126.25
CO2CH2CH3), 4.32 and 4.33 (q, J = 7.1 Hz, 4 H, 2 CO2CH2CH3),
6.63 (d, J = 9.2 Hz, 2 H, 3Ј,5Ј-H), 7.51 (d, J = 9.2 Hz, 2 H, 2Ј,6Ј-
(2 C, C-2Ј,6Ј), 148.20 (1 C, C-6), 151.57 (1 C, C-4Ј), 158.66 (1 C,
C=O), 163.79 (1 C, C-2), 169.39 (2 C, C=O) ppm. IR (ATR): ν =
˜
H), 8.16 (s, 1 H, C-1) ppm. 13C NMR (100 MHz, CDCl3): δ = 13.80 2983 (w), 1735 (s), 1687 (m), 1608 (s), 1526 (m), 1444 (w), 1366
(1 C, CO2CH2CH3), 14.16 and 14.23 (2 C, 2 CO2CH2CH3), 40.04 (m), 1223 (s), 1196 (s), 1170 (m), 1076 (s), 1041 (s), 946 (w), 911
Eur. J. Org. Chem. 2015, 7264–7275
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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