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DOI: 10.1055/s-2008-1078244
Synthesis of Isoxazoline-Fused Bicyclic Enediynes via Intramolecular Nitrile Oxide-Alkene Cycloaddition
Publication History
Publication Date:
31 July 2008 (online)
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Abstract
The intramolecular nitrile oxide-alkene cycloaddition has been studied in an enediyne system. It has been shown to be an efficient method for one-step synthesis of isoxazoline-fused bicyclic enediynes. The thermal reactivity of these enediynes is similar to the isoxazolidine-fused counterparts, thus ruling out any significant effect by the bridgehead double bond.
Key word
enediyne - cycloaddition - Bergman cyclization - intramolecular - activation
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References and Notes
ArgusLab version 4.0.1, Thomson and Planaria Software LLC.
12
Selected Spectroscopic
Data: Compound 11: ¹H NMR (400 MHz): δ = 1.22
(t, J = 7.0 Hz, 3 H, COOCH2CH
3), 2.64-2.76 (m,
1 H, CHCH
2COOEt), 3.20-3.22
(m, 2 H, CCCH
2CH), 3.82-3.89
(m, 2 H, CCCHCH2NO2),
4.26 (q, J = 7.2
Hz, 2 H, COOCH
2CH3),
4.55-4.66 (m, 2 H, CHCH
2NO2),
5.13 (dd, J = 1.6, 10.0 Hz,
1 H, CH2CHCH
2), 5.40
(dd, J = 2.0, 17.2 Hz, 1 H,
CH2CHCH
2), 5.84-5.
90 (m, 1 H, CH2CH=CH2),
7.12-7.19 (m, 2 H, ArH), 7.28-7.38 (m, 2 H, ArH). ¹³C
NMR (100 MHz): δ = 0.96, 14.1,
30.1, 31.7, 36.4, 61.2, 81.2, 83.3, 88.6, 90.9, 115.7, 125.1, 126.2,
126.5, 128.2, 128.7, 130.8, 140.7, 170.0. MS (ESI): m/z = 325 [M+].
Compound 1A: ¹H NMR
(400 MHz): δ = 1.29 (t, J = 6.0
Hz, 3 H, COOCH2CH
3),
2.68 (dd, J = 7.2, 12.8 Hz,
1 H, Hg), 2.74 (dd, J = 3.2,
14.8 Hz, 1 H, Hd), 2.83 (dd, J = 5.6,
12.8 Hz, 1 H, Hh), 2.91 (dd, J = 1.6,
14.8 Hz, 1 H, He), 3.20 (dd, J = 8.4, 13.2
Hz, 1 H, Hc), 3.60 (dd, J = 2.8,
13.2 Hz, 1 H, Hb), 4.20 (q, J = 5.6
Hz, 2 H, COOCH
2CH3),
4.45 (dd, J = 1.6, 5.6 Hz, 1
H, Hf), 4.93-4.97 (m, 1 H, Ha), 7.21-7.29
(m, 2 H, ArH), 7.34-7.36 (m, 2 H, ArH). ¹³C
NMR (100 MHz): δ = 14.1, 27.3, 28.7, 29.6, 35.7,
36.3, 61.2, 81.6, 85.0, 88.4, 92.0, 124.9, 127.6, 128.1, 128.2,
129.1, 130.8, 155.5, 169.7. MS (ESI): m/z = 330 [M + Na+].
HRMS: m/z calcd
for C19H18NO3 [M + H+]:
308.3512; found: 308.3510.
Compound
1B: ¹H NMR (400 MHz): δ = 1.28
(t, J = 5.6 Hz, 3 H, COOCH2CH
3), 2.72 (dd, J = 3.4, 14.6 Hz, 1 H, He),
2.91 (dd, J = 3.2, 14.6 Hz,
1 H, Hd), 2.95 (dd, J = 1.6,
14.4 Hz, 1 H, Hg), 3.23 (dd, J = 4.8,
14.4 Hz, 1 H, Hh), 3.30 (dd, J = 7.2, 14.0
Hz, 1 H, Hb), 3.63 (dd, J = 2.8,
14.0 Hz, 1 H, Hc), 3.96 (dd, J = 4.8,
7.2 Hz, 1 H, Hf), 4.20 (q, J = 2.4
Hz, 2 H, COOCH
2CH3),
4.92-4.96 (m, 1 H, Ha), 7.20-7.29 (m,
2 H, ArH), 7.34-7.36 (m, 2 H, ArH). ¹³C
NMR (100 MHz): δ = 14.1, 27.2, 28.5, 29.6, 35.6,
39.9, 60.9, 81.5, 84.9, 88.6, 92.3, 125.0, 127.6, 128.0, 128.3,
129.1, 130.8, 156.3, 171.0. MS (ESI): m/z 330 [M + Na+].
HRMS: m/z calcd
for C19H18NO3 [M + H+]:
308.3512; found: 308.3509.