S. Ghiassian, P. Gobbo, M. S. Workentin
FULL PAPER
propriate nitrone (5 equiv.) A–E. The mixture was then transferred
1
Isoxazolidine 4D-exo: H NMR (400 MHz, CD3CN): δH = 2.21 (s,
3 H), 3.26 (m, 5 H), 3.42–3.48 (m, 10 H), 3.99 (dd, 1 H), 4.70 (d,
1 H), 5.11 (d, 1 H), 6.31 (m, 2 H), 6.88 (d, 2 H), 7.02 (d, 2 H), 7.41
(dd, 1 H) ppm. 13C NMR (400 MHz CDCl3): δC = 38.3, 53.6, 58.9,
63.9, 66.5, 70.1, 70.4, 70.5, 71.9, 76.2, 108.9, 110.5, 116.0, 125.3,
129.2, 132.8, 142.6, 150.0, 174.7 ppm. One of the carbonyl carbons
was too weak to see. HRMS: calcd. m/z for C23H28N2O7 444.1887,
found 444.1898.
Isoxazolidine 4E-endo: 1H NMR (400 MHz, CD3CN): δH = 2.51 (s,
3 H), 3.28 (s, 3 H), 3.45 (m,2 H), 3.53–3.58 (m 10 H), 3.67 (t, 1 H),
3.75 (d, 1 H), 4.83 (d, 1 H), 5.95 (d, 2 H), 6.77 (m, 3 H) ppm. 13C
NMR (400 MHz CDCl3): δH = 38.2, 42.4, 54.2, 59.0, 66.8, 69.9,
70.5, 71.9, 75.2, 76.2, 101.2, 107.8, 108.4, 121.6, 127.0, 147.9, 173.0,
175.6 ppm. HRMS: calcd. m/z for C20H26N2O8 422.1680, found
422.1700.
1
to a NMR tube and placed in a 37 °C bath. After H NMR spec-
troscopy showed reaction completion, the reaction was stopped by
evaporating the solvent and forming a film of AuNPs. The products
2(A–E)-AuNPs were then purified by washing the film with cyclo-
hexane and then with 2-propanol to remove any unreacted nitrone.
1H NMR spectroscopy was used to characterize the resulting 2-
AuNPs. These spectra were then compared to those of the products
of the model reaction to ensure purity. All the NMR spectra are
provided in the supporting information.
Preparation of 4A–4E: Compound 3 (20 mg, 1 equiv.) and nitrones
A–E (5 equiv.) were dissolved in deuterated acetonitrile (2 mL). The
mixture was then transferred to a NMR tube and placed in a 37 °C
bath. After 1H NMR spectroscopy showed reaction completion,
the reaction was stopped and the product was purified by prepara-
tive TLC plate (20–50% gradient of hexanes to ethyl acetate). The
resulting products were then characterized by 1H and 13C NMR
spectroscopy and high resolution mass spectrometry. All the NMR
spectra are provided in the supporting information.
1
Isoxazolidine 4E-exo: H NMR (400 MHz, CD3CN): δH = 2.37 (b,
3 H), 3.28 (s, 3 H), 3.44 (m, 2 H), 3.49–3.70 (m, 12 H), 4.91 (b, 1
H), 5.98 (s, 2 H), 6.84 (m, 3 H) ppm. 13C NMR (400 MHz, CDCl3):
δC = 38.3, 42.3, 56.9, 59.0, 66.8, 70.0, 70.5 (ϫ2), 71.9, 75.8, 101.3,
108.4, 122.2, 129.7, 147.8, 148.1, 175.1 ppm. One of the carbonyl
carbons was too weak to see. HRMS: calcd. m/z for C20H26N2O8
422.1680, found 422.1692.
1
Isoxazolidine 4A-endo: H NMR (400 MHz, CD3CN): δ = 3.27 (s,
3 H), 3.43 (dd, 2 H), 3.53–3.59 (m, 12 H), 3.77 (s,3 H), 3.9 (dd, 1
H), 4.67 (d, 1 H), 5.10 (d, 1 H), 6.87 (d, 2 H), 7.10 (m, 3 H), 7.25
(m, 4 H) ppm. 13C NMR (400 MHz CD3CN): δC = 39.6, 55.7, 56.3,
59.3, 67.8, 71.3, 71.4, 71.5, 72.6, 72.9, 78.2, 115.2, 121.9, 126.8,
127.9, 130.0, 130.7, 148.8, 161.1, 174.5, 176.5 ppm. HRMS: calcd.
m/z for C25H30N2O7 470.2043, found 470.2040.
Isoxazolidine 4A-exo: 1H NMR (400 MHz, CD3CN): δH = 3.24–
3.32 (m, 5 H), 3.42–3.49 (m, 10 H), 3.75 (s,3 H), 3.87 (m, 1 H),
5.13 (d, 1 H), 5.36 (d, 1 H), 6.87 (d, 2 H), 6.90 (t, 1 H), 6.98 (d, 2
H), 7.18 (t, 2 H), 7.33 (d, 2 H) ppm. 13C NMR (400 MHz CD3CN):
δC = 39.6, 56.3, 57.9, 59.3, 67.5, 70.4, 71.3, 71.4, 72.9, 78.2, 115.2,
116.7, 123.8, 130.2, 131.8, 149.3, 160.8, 175.6, 176.6 ppm. HRMS:
calcd. m/z for C25H30N2O7 470.2043, found 470.2038.
Isoxazolidine 4B-endo: 1H NMR (400 MHz, CD3CN): δH = 2.51 (s,
3 H), 3.28 (s, 3 H), 3.45 (m, 2 H), 3.53–3.58 (m, 10 H), 3.73 (t, 1
H), 3.81 (d, 1 H), 4.87 (d, 1 H), 7.24 (m, 2 H), 7.33 (m, 3 H) ppm.
13C NMR (400 MHz CD3CN): δC = 39.6, 43.4, 55.6, 59.3, 67.9,
71.3, 71.5, 73.0, 76.5, 78.0, 129.6, 129.7, 129.8, 135.9, 174.8,
177.0 ppm. HRMS: calcd. m/z for C19H26N2O6 378.1782, found
378.1797.
Diels–Alder Reactions
Preparation of 3-AuNPs: Mal-EG4-AuNPs (10 mg, 1 equiv.) was
dissolved in deuterated acetonitrile (1 mL) and mixed the appropri-
ate diene (5 equiv.) F–J. The mixture was then transferred to a
NMR tube and placed in a 37 °C bath. After 1H NMR spec-
troscopy showed reaction completion, the reaction was stopped by
evaporating the solvent and forming a film of AuNPs. The products
3(F–J)-AuNPs were then purified by washing the film with cyclo-
hexane and then 2-propanol to remove any unreacted diene. 1H
NMR spectroscopy was used to characterize the resulting 3-
AuNPs. These spectra were then compared to those of the products
of the model reaction to ensure purity. All the NMR spectra are
provided in the supporting information.
Preparation of 5F–5J: Compound 3 (20 mg, 1 equiv.) and dienes F–
J (5 equiv.) were dissolved in 2 mL of deuterated acetonitrile. The
mixture was then transferred to a NMR tube and placed in a 37 °C
bath. After 1H NMR spectroscopy showed reaction completion,
the reaction was stopped and the product was purified by prepara-
tive TLC plate (20–50% gradient of hexanes to ethyl acetate). The
resulting products were then characterized by NMR spectroscopy.
All the NMR spectra are provided in the supporting information.
Cycloadduct 5F: 1H NMR (400 MHz, CD3CN): δH = 2.4 (m, 2 H),
3.06 (m, 1 H), 3.12 (m, 1 H), 3.22 (s, 3 H), 3.28 (s, 3 H), 3.44 (m,
2 H), 3.48–3.57 (m, 10 H), 4.14 (m, 1 H), 6.06 (m, 2 H) ppm. 13C
NMR (400 MHz CD3CN): δC = 23.5, 38.2, 39.1, 45.4, 57.1, 59.3,
68.1, 71.3, 71.4, 73.0, 73.4, 130.2, 132.0, 177.8, 181.3 ppm. HRMS:
calcd. m/z for C16H25NO6 327.1674, found 327.1692.
Cycloadduct 5G: 1H NMR (400 MHz, CD3CN): δH = 1.28 (d, 3
H), 2.16 (m, 1 H), 2.45–2.55 (m, 2 H), 3.00 (dd, 1 H), 3.10 (dt, 1
H), 3.28 (s, 3 H), 3.43–3.53 (m, 12 H), 5.71 (m, 1 H), 5.81 (m, 1
H) ppm. 13C NMR (400 MHz, CD3CN): δC = 17.0, 24.3, 30.8,
38.6, 40.9, 44.8, 58.8, 67.7, 70.9 (ϫ2), 72.5, 127.7, 135.5, 178.9,
180.7 ppm. HRMS: calcd. m/z for C16H25NO5 311.1725, found
311.1741.
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Isoxazolidine 4B-exo: H NMR (400 MHz, CD3CN): δH = 2.41 (b,
3 H), 3.28 (s, 3 H), 3.45 (m, 2 H), 3.50–3.68 (m, 11 H), 3.75 (dd, 1
H), 4.96 (b, 1 H), 7.41 (m, 5 H) ppm. 13C NMR (400 MHz CDCl3):
δC = 38.3, 58.9, 66.8, 70.0, 70.5, 71.9, 76.0, 128.3, 128.6, 128.8,
136.1, 175.1 ppm. two carbons could not be observed due to the
weakness of the signals. HRMS: calcd. m/z for C19H26N2O6
378.1782, found 378.1789.
Isoxazolidine 4C: 1H NMR (400 MHz, CD3CN): δH = 2.77 (b, 1
H), 3.28 (s, 3 H), 3.55–3.65 (m, 14 H), 3.76 (s, 3 H), 3.87 (s, 2 H),
4.76 (d, 1 H), 6.86 (d, 2 H), 7.2 (d, 2 H) ppm. 13C NMR (400 MHz
CD3CN): δC = 39.5, 56.2, 59.2, 68.0, 71.33, 71.37, 71.4, 72.9, 114.9,
130.2, 131.3, 160.4, 177.9 ppm. HRMS: calcd. m/z for C20H28N2O7
408.1887, found 408.1907.
Isoxazolidine 4D-endo: 1H NMR (400 MHz, CD3CN): δH = 2.25
(s, 3 H), 3.27 (s, 3 H), 3.43 (m, 2 H), 3.51–3.63 (m, 10 H), 3.88 (dd,
1 H), 4.70 (d, 1 H), 5.09 (d, 1 H), 6.33 (m, 2 H), 6.92 (d, 2 H), 7.08
(d, 2 H), 7.46 (dd, 1 H) ppm. 13C NMR (400 MHz CDCl3): δC
=
Cycloadduct 5H: 1H NMR (400 MHz, CD3CN): δH = 1.64 (s, 6 H),
38.1, 54.5, 55.1, 58.9, 66.6, 70.0, 70.50, 70.54, 71.1, 71.9, 76.5,
2.29 (m, 4 H), 3.02 (m, 2 H), 3.30 (s, 3 H), 3.45–3.55 (m, 12 H)
114.2, 119.4, 124.8, 126.1, 128.6, 128.7, 142.2, 159.7, 172.5, ppm. 13C NMR (400, MHz CD3CN): δC = 19.9, 31.8, 39.3, 41.1,
174.6 ppm. HRMS: calcd. m/z for C23H28N2O7 444.1887, found 59.3, 68.2, 71.2, 71.4, 73.0, 128.0, 181.5 ppm. HRMS: calcd. m/z
444.1902.
for C17H27NO5 325.1881, found 325.1883.
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Eur. J. Org. Chem. 2015, 5438–5447