Mendeleev Commun., 2017, 27, 29–30
unsuccessful. For example, attempted isomerization of 2b by
n
n
n
MeSO3H
CH2Cl2
m-CPBA
CH2Cl
neat application of CF3COOH (6 equiv.), MeSO3H (3 equiv.)/
CH2Cl2, TMSOTf (3 equiv.)/CH2Cl2 resulted in formation of
complex reaction mixture and tarring. Also in reactions with
BF3·Et2O (1 equiv.)/CH2Cl2, ZnCl2 (1 equiv.)/CH2Cl2, TMSOTf
(0.2 equiv.)/CH2Cl2, TsOH (1 equiv.)/CH2Cl2, CF3COOH
(1 equiv.)/CH2Cl2, CF3SO3H (1 equiv.)/CH2Cl2 no isomeriza-
tion was observed. Therefore, additional investigations in this
field will be necessary in future.
R
N
R
R
2
N
N
O
O
3e–i,k
1a–k
2a–k
n = 1–3
Imine
n
R
Bu
cyclohexyl
Oxaziridine
Nitrone
1a
1b
1c
1d
1e
1f
1g
1h
1i
1
1
1
1
1
1
1
2
2
3
3
2a (62%)
2b (87%)
1-adamantyl
2c
(96%)
This work was supported by the Russian Foundation for Basic
Research and Moscow city Government (project no. 15-33-70009
‘mol_a_mos’).
2-MeC6H4CH2 2d (82%)
Ph
(94%)
(76%)
(93%)
(77%)
(76%)
(77%)
(85%)
3e (99%)
3f (97%)
3g (99%)
3h (47%)
3i (99%)
2e
2f
2g
2h
2i
4-MeOC6H4
4-FC6H4
cyclohexyl
Ph
Bu
Ph
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi: 10.1016/j.mencom.2017.01.008.
2j
2k
1j
1k
3k (99%)
Scheme 1
References
1
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mixture was necessary in the case of aryl-substituted imines 1f
and 1g to prevent side transformations.
Then we investigated the rearrangement of prepared oxazi-
ridines 2a–k into the corresponding nitrones 3a–k (see Scheme 1).‡
According to our experiments, aryl-substituted oxaziridines 2e–g
and 2k were converted efficiently (up to 99% yields) into nitrones
3e–g and 3k using excess of methanesulfonic acid (3 equiv.) at
room temperature. In the case of alkyl-substituted oxaziridines
2a–d and 2j the reaction was more complicated and no desired
products were isolated. Only oxaziridine 2h containing alkyl
group and bearing six-membered ring turned into target nitrones
3h in the presence of excess of methanesulfonic acid in 47%
yield. We tried some other conditions for isomerization of imines
with aliphatic substituents. However, in all cases the results were
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‡
General procedure for rearrangement of oxaziridines into nitrones.
Methanesulfonic acid (1.54 mmol, 0.1 ml for 2e–g,i,k and 1–2 ml for 2h)
was added to solution of oxaziridine (0.5 mmol) in CH2Cl2 (2–4 ml). The
reaction mixture was stirred overnight, except for 2h (several days, TLC
control).
5-Phenyl-3,4-dihydro-2H-pyrrole 1-oxide 3e: 99%, white solid,
mp 100–102°C. 1H NMR (400 MHz, CDCl3) d: 2.13 (qt, 2H, 3JHH 7.7 Hz),
3.08–3.11 (m, 2H), 4.16 (t, 2H, CH2N, 3JHH 8.0 Hz), 7.34–7.41 (m, 3H,
HAr), 8.27–8.29 (m, 2H, HAr). 13C NMR (100 MHz, CDCl3) d: 16.4,
30.7, 64.8 (CH2N), 126.9 (Ph), 128.1 (Ph), 129.0 (C=N+), 129.9 (Ph),
140.0 (Cq–Ar). IR (ATR, ZnSe, n/cm–1): 2951, 1569, 1435, 1223, 768,
694. HRMS (ESI), m/z: 162.0914 [M+H]+ (calc. for C10H12NO+, m/z:
162.0914).
5-(4-Methoxyphenyl)-3,4-dihydro-2H-pyrrole 1-oxide 3f: 97%, white
solid, mp 157–159°C. 1H NMR (400 MHz, CDCl3) d: 2.10 (qt, 2H,
3JHH 7.8 Hz), 3.03–3.07 (m, 2H), 3.77 (s, 3H, OMe), 4.10–4.14 (m, 2H,
CH2N), 6.86–6.89 (m, 2H, HAr), 8.26–8.28 (m, 2H, HAr). 13C NMR
(100 MHz, CDCl3) d: 16.3, 30.7, 55.1, 64.3 (CH2N), 113.4 (Ar), 122.0
(Cq–Ar), 128.9, 139.9 (C=N+), 160.6 (Cq–Ar). IR (ATR, ZnSe, n/cm–1):
2957, 1602, 1509, 1250, 1026, 834. HRMS (ESI), m/z: 192.1021 [M+H]+
(calc. for C11H12NO2+, m/z: 192.1020).
For characteristics of compounds 3g–i,k, see Online Supplementary
Materials.
Received: 20th October 2016; Com. 16/5079
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