10.1002/ejoc.202100469
European Journal of Organic Chemistry
FULL PAPER
CDCl3): δ 0.19 (s, 6H, Me2Si), 0.97 (s, 9H, t-BuSi), 1.20-1.25 (m, 9H,
3×CH3), 2.56 (dd, J = 15.7, 7.6 Hz, 1H, CH2a), 2.83 (dd, J = 15.7, 7.3 Hz,
1H, CH2b), 3.48 (app sext, J = 7.3 Hz, 1H, CHMe), 4.99 (hept, J = 6.3 Hz,
1H, OCH(CH3)2), 5.35 (d, J = 11.2 Hz, 1H, =CH2cis), 5.68 (d, 1H, J = 17.7
Hz, =CH2trans), 6.33 (dd, J = 17.7, 11.2 Hz, 1H, =CH). 13C NMR (75 MHz,
DEPT, CDCl3): δ -5.3 (Me2Si), 16.5 (CHMe), 18.0 (Me3C−Si), 21.8
(2×CH3), 26.1 (Me3C), 28.8 (CHMe2), 38.3 (CH2), 67.6 (Me2CH−O),
118.0 (=CH2), 133.0 (=CH), 163.6 (C=N), 171.9 (C=O). HRMS (ESI): m/z
calcd. for [C16H31NO3Si + H+]: 314.2146, found: 314.2154.
2-(((tert-Butyldimethylsilyl)oxy)imino)cyclopentyl acetate 2sa. Oxime
ether 2sa was obtained from nitro compound 1s (41 mg, 0.36 mmol),
acetyl chloride (30 µL, 34 mg, 0.43 mmol) and TBSOTf (0.14 mL, 0.16 g,
0.61 mmol) according to GP-4. Column chromatography (eluent: PE,
then PE/EtOAc, 50:1) afforded 80 mg (82%) of target oxime ether as
colorless oil. Rf = 0.44 (PE/EtOAc, 9:1, anisaldehyde). 1H NMR (300
MHz, CDCl3): δ 0.16 (s, 3H, MeSi), 0.17 (s, 3H, MeSi), 0.93 (s, 9H,
t-BuSi), 1.72-2.06 (m, 4H, 2×CH2), 2.06 (s, 3H, CH3CO), 2.47 (ddd, J =
19.2, 8.1, 6.3 Hz, 1H, CH2a), 2.54-2.65 (m, 1H, CH2b), 5.54 (t, J = 5.0 Hz,
1H, CH−O). 13C NMR (75 MHz, DEPT, HMBC, CDCl3): δ -5.29 (MeSi), -
5.27 (MeSi), 18.1 (Me3CSi), 20.6 (CH2), 21.1 (MeCO), 26.0 (Me3C), 26.3
(CH2), 32.2 (CH2), 73.8 (CH−O), 166.6 (C=N), 170.1 (C=O). HRMS (ESI):
m/z calcd. for [C13H25NO3Si + H+]: 272.1680, found: 272.1676.
rel-(7S,9R)-8-(((tert-Butyldimethylsilyl)oxy)imino)-9-(4-
methoxyphenyl)-1,4-dioxaspiro[4.5]decan-7-yl pivalate 2w. Oxime
ether 2w was obtained from nitro compound 1w (89 mg, 0.30 mmol),
pivaloyl chloride (45 µL, 43 mg, 0.36 mmol) and TBSOTf (0.12 mL, 0.14
g, 0.52 mmol) according to GP-5 with following change: silylation stage
was prolonged to 4 h. Column chromatography (eluent: PE/EtOAc, 9:1)
afforded 115 mg (76%) of target oxime ether as slightly yellow oil.
Relative configuration was assigned based on coupling constants for
CH(7) and CH(9) and NOESY specta assuming a chair-like conformation.
Rf = 0.51 (PE/EtOAc, 3:1, UV, anisaldehyde). Two conformers in a ratio
4:1.Major conformer: 1H NMR (300 MHz, COSY, NOESY, CDCl3): δ 0.00
(s, 3H, MeSi), 0.07 (s, 3H, MeSi), 0.71 (s, 9H, t-BuSi), 1.21 (s, 9H, t-Bu),
2.10 (dd, J = 13.5, 6.2 Hz, 1H, CH2ax(10)), 2.26-2.37 (m, 3H, CH2eq(10)
and CH2(6)), 3.78 (s, 3H, OMe), 3.86-3.97 (m, 4H, OCH2CH2O), 4.29 (dd,
J = 12.1, 6.5 Hz, 1H, CH(9)axAr), 5.65 (dd, J = 4.7, 2.6 Hz, 1H,
CHeq(7)−OPiv), 6.80 (d, J = 8.7 Hz, 2H, CHAr), 7.19 (d, J = 8.7 Hz, 2H,
CHAr). 1H NMR (300 MHz, CD3CN): δ 0.00 (s, 3H, MeSi), 0.07 (s, 3H,
MeSi), 0.71 (s, 9H, t-BuSi), 1.15 (s, 9H, t-Bu), 2.16-2.35 (m, 4H, CH2(6)
and CH2(10)), 3.73 (s, 3H, OMe), 3.82-3.98 (m, 4H, OCH2CH2O), 4.26
(dd, J = 11.1, 7.7 Hz, 1H, CHax(9)Ar), 5.56 (dd, J = 5.8, 1.9 Hz, 1H,
CHeq(7)−OPiv), 6.81 (d, J = 8.7 Hz, 2H, CHAr), 7.17 (d, J = 8.7 Hz, 2H,
CHAr). 13C NMR (75 MHz, DEPT, HSQC, HMBC, CDCl3): δ -5.4 (Me2Si),
17.8 (Me3C−Si), 25.7 (Me3CSi), 27.1 (Me3CC(O)), 38.6 (CH(9)−Ar), 38.8
(Me3C), 39.2 (CH2(10)), 41.4 (CH2(6)), 55.3 (OMe), 64.1 and 64.4
(OCH2CH2O), 71.7 (CH(7)–O), 107.5 (CH(OCH2)2), 113.6 (CHAr), 128.0
(CHAr), 134.2 (CAr), 157.9 (CAr), 159.8 (C=N), 177.0 (C=O). Minor
conformer: 1H NMR (300 MHz, COSY, NOESY, CDCl3): δ 0.03 (s, 3H,
MeSi), 0.12 (s, 3H, MeSi), 0.78 (s, 9H, t-BuSi), 1.28 (s, 9H, t-Bu), 2.06-
2.17 (m, 2H) and 2.24-2.37 (m, 2H) (CH2(6) and CH2(10)), 3.78 (s, 3H,
OMe), 3.86-3.97 (m, 4H, OCH2CH2O), 4.79 (app t, J = 5.9 Hz, 1H,
CH(9)eqAr), 5.68 (dd, J = 12.2, 6.2 Hz, 1H, CHax(7)−OPiv), 6.84 (d, J =
8.7 Hz, 2H, CHAr), 7.22 (d, J = 8.7 Hz, 2H, CHAr). Characteristic NOESY
interactions: CH(7)−O / CHAr. 1H NMR (300 MHz, CD3CN): δ 0.01 (s, 3H,
MeSi), 0.09 (s, 3H, MeSi), 0.77 (s, 9H, t-BuSi), 1.23 (s, 9H, t-Bu), 2.01-
2.35 (m, 4H, CH2(6) and CH2(10)), 3.75 (s, 3H, OMe), 3.82-3.98 (m, 4H,
OCH2CH2O), 4.67 (app t, J = 6.5 Hz, 1H, CHeq(9)Ar), 5.62 (dd, J = 11.8,
6.6 Hz, 1H, CHax(7)−OPiv), 6.84 (d, J = 8.8 Hz, 2H, CHAr), 7.23 (d, J =
8.8 Hz, 2H, CHAr). 13C NMR (75 MHz, DEPT, HSQC, HMBC, CDCl3,
characteristic signals): δ -5.3 (MeSi), 17.9 (Me3C−Si), 25.9 (Me3CSi),
27.3 (Me3CC(O)), 36.1 (CH(9)−Ar), 38.1 and 40.8 (CH2(6) and CH2(10)),
55.2 (OMe), 64.2 and 64.5 (OCH2CH2O), 68.0 (CH(7)–O), 107.8
(CH(OCH2)2), 113.7 (CHAr), 128.0 (CHAr). HRMS (ESI): m/z calcd. for
[C26H41NO6Si + H+]: 492.2776, found: 492.2779.
2-(((tert-Butyldimethylsilyl)oxy)imino)cyclopentyl
2-chloroacetate
2sb. Oxime ether 2sb was obtained from nitro compound 1s (40 mg,
0.35 mmol), chloroacetyl chloride (33 µL, 47 mg, 0.42 mmol) and
TBSOTf (0.13 mL, 0.15 g, 0.57 mmol) according to GP-4. Column
chromatography (eluent: PE, then PE/EtOAc, 50:1) afforded 80 mg
(76%) of target oxime ether as slightly yellow oil. Rf = 0.41 (PE/EtOAc,
1
9:1, UV, anisaldehyde). E/Z ≈ 1:1. E-isomer: H NMR (300 MHz, COSY,
CDCl3): δ 0.15 (s, 3H, MeSi), 0.16 (s, 3H, MeSi), 0.93 (s, 9H, t-BuSi),
1.69-2.16 (m, 4H, 2×CH2), 2.37-2.67 (m, 2H, CH2), 4.06 (s, 2H, CH2Cl),
5.62 (t, J = 4.5 Hz, 1H, CH−O).13C NMR (75 MHz, DEPT, HSQC, CDCl3):
δ -5.3 (Me2Si), 18.0 (Me3CSi), 20.7 (CH2), 26.0 (Me3C), 26.2 (CH2–C=N),
32.1 (CH2), 40.9 (CH2Cl), 75.6 (CH−O), 165.8 and 166.0 (C=N and C=O).
Z-isomer: 1H NMR (300 MHz, COSY, CDCl3,): δ 0.15 (s, 3H, MeSi), 0.17
(s, 3H, MeSi), 0.91 (s, 9H, t-BuSi), 1.69-2.16 (m, 4H, 2×CH2), 2.37-2.67
(m, 2H, CH2), 4.02 (s, 2H, CH2Cl), 5.98 (dd, J = 6.7, 3.9 Hz 1H, CH−O).
13C NMR (75 MHz, DEPT, HSQC, CDCl3): δ -5.3 (Me2Si), 18.1 (Me3CSi),
22.2 (CH2), 25.9 (Me3C), 29.5 (CH2–C=N), 32.3 (CH2), 40.8 (CH2Cl), 70.2
(CH−O), 165.0 and 166.4 (C=N and C=O). HRMS (ESI): m/z calcd. for
[C13H24ClNO3Si + H+]: 306.1287, found: 306.1290.
2-(((tert-Butyldimethylsilyl)oxy)imino)cyclopentyl isobutyrate 2sc.
Oxime ether 2sc was obtained from nitro compound 1s (43 mg, 0.37
mmol), isobutyryl chloride (47 µL, 47 mg, 0.45 mmol) and TBSOTf (0.14
mL, 0.17 g, 0.63 mmol) according to GP-4. Column chromatography
(eluent: PE, then PE/EtOAc, 50:1) afforded 95 mg (86%) of target oxime
1
ether as colorless oil. Rf = 0.49 (PE/EtOAc, 9:1, anisaldehyde). H NMR
(300 MHz, CDCl3): δ 0.148 (s, 3H, MeSi), 0.154 (s, 3H, MeSi), 0.92 (s,
9H, t-BuSi), 1.16 (d, J = 7.0 Hz, 6H, CHMe2), 1.69-1.94 (m, 3H) and 1.98-
2.06 (m, 1H) (2×CH2), 2.41-2.65 (m, 3H, CH2 and CHMe2), 5.55 (t, J =
5.4 Hz, 1H, CH−O). 13C NMR (75 MHz, DEPT, HMBC, CDCl3): δ -5.32
(MeSi), -5.28 (MeSi), 18.1 (Me3C−Si), 18.8 and 18.9 (Me2CH), 20.6 (CH2),
26.0 (Me3C), 26.3 (CH2), 32.2 (CH2), 34.0 (Me2CH), 73.4 (CH−O), 166.5
(C=N), 176.1 (C=O). HRMS (ESI): m/z calcd. for [C15H29NO3Si + Na+]:
322.1806, found: 322.1809.
2-(((tert-Butyldimethylsilyl)oxy)imino)cyclopentyl
(3r,5r,7r)-
adamantane-1-carboxylate 2sd. Oxime ether 2sd was obtained from
nitro compound 1s (53 mg, 0.46 mmol), adamantanecarbonyl chloride
(110 mg, 0.55 mmol) and TBSOTf (0.18 mL, 0.21 g, 0.78 mmol)
according to GP-4. Column chromatography (eluent: PE, then PE/EtOAc
90:1) afforded 137 mg (76%) of target oxime ether as colorless oil, which
2-(((tert-Butyldimethylsilyl)oxy)imino)-3-(4-methoxyphenyl)propyl
acetate 2ba. Oxime ether 2ba was obtained from nitro compound 1b
(168 mg, 0.86 mmol), acetyl chloride (74 µL, 81 mg, 1.04 mmol) and
TBSOTf (0.34 mL, 0.39 g, 1.48 mmol) according to GP-3. Column
chromatography (eluent: PE/EtOAc, 20:1) afforded 238 mg (79%) of
target oxime ether as slightly yellow oil. Rf = 0.44 (PE/EtOAc, 9:1, UV,
anisaldehyde). 1H NMR (300 MHz, CDCl3): δ 0.21 (s, 6H, Me2Si), 0.97 (s,
9H, t-BuSi), 2.04 (s, 3H, MeC(O)), 3.74 (s, 2H, CH2−Ar), 3.80 (s, 3H,
OCH3), 4.60 (s, 2H, CH2−O), 6.83 (d, J = 8.6 Hz, 2H, CHAr), 7.14 (d, J =
8.6 Hz, CHAr). 13C NMR (75 MHz, DEPT, HMBC, CDCl3): δ -5.2 (Me2Si),
18.1 (Me3C−Si), 20.7 (MeC(O)), 26.0 (Me3CSi), 31.1 (CH2), 55.2 (MeO),
63.9 (CH−O), 114.0 (CHAr), 128.2 (CAr), 130.1 (CHAr), 158.2 and 158.3
(CAr–OMe and C=N), 170.3 (C=O). HRMS (ESI): m/z calcd. for
[C18H29NO4Si + H+]: 352.1938, found: 352.1939.
solidified upon storage in
a fridge. Rf = 0.53 (PE/EtOAc, 9:1,
anisaldehyde).mp = 54-56 °C (PE). 1H NMR (300 MHz, CDCl3): δ 0.16 (s,
3H, MeSi), 0.17 (s, 3H, MeSi), 0.94 (s, 9H, t-BuSi), 1.67-2.06 (m, 19 H,
all CH2Ad, all CHAd, 2×CH2), 2.42-2.66 (m, 2H, CH2), 5.53 (t, J = 5.3 Hz,
1H, CH−O). 13C NMR (75 MHz, DEPT, HMBC, CDCl3): δ -5.3 (MeSi), -
5.2 (MeSi), 18.2 (Me3C−Si), 20.7 (CH2), 26.1 (Me3C), 26.3 (CH2), 28.0
(CHAd), 32.2 (CH2), 36.5 and 38.8 (CH2Ad), 40.7 (CAd), 73.2 (CH−O),
166.6 (C=N), 176.6 (C=O). HRMS (ESI): m/z calcd. for [C22H37NO3Si +
Na+]: 414.2435, found: 414.2429.
2-(((tert-Butyldimethylsilyl)oxy)imino)cyclopentyl benzoate 2se.
Oxime ether 2se was obtained from nitro compound 1s (44 mg, 0.38
mmol), benzoyl chloride (53 µL, 64 mg, 0.46 mmol) and TBSOTf (0.15
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