, 2005, 15(3), 116–118
Schiff base 8, which reacts with N-chloroalkylamine 3 to give
N-chloroaminal 5 (Scheme 2). Unlike the well-known methods
for the synthesis of diaziridines,1–5 it takes much longer (48–60 h)
to complete the process under these conditions.
At first glance, the low yields of 1,2-dialkyldiaziridines 1
from 1,3,5-trialkylhexahydro-1,3,5-triazines 6 and N-chloro-
alkylamines 3 in aqueous media seem unexpected, since an
excess of water should favour ring opening in the molecule of 6
and thus facilitate the reaction as a whole. However, additional
kinetic studies‡ demonstrated that the stability of N-chloro-
alkylamines 3 in weakly basic aqueous media is low (MeNHCl
3a, Edecomp = 17.8 kcal mol–1, n = 1) in comparison with the
stability in chloroform (Edecomp = 22 kcal mol–1, n = 0); the for-
mally estimated decomposition rates of compound 3a at 20 °C
differ by more than two orders of magnitude in these solvents.
This is probably the decisive circumstance in the successful
synthesis of 1,2-dialkyldiaziridines 1 from 1,3,5-trialkylhexa-
hydro-1,3,5-triazines 6 and N-chloroalkylamines 3 in organo-
chlorine media.
The reactions of N-chloroalkylamines 3a–c with primary
aliphatic amines containing the same alkyl fragment in the
absence of a carbonyl compound unexpectedly gave 1,2,3-tri-
alkyldiaziridines 2b,c from N-chloroethyl- and N-chloropropyl-
amines 3b,c in 81 and 98% yields, respectively, and 1,2-di-
methyldiaziridine 1a from N-chloromethylamine 3a in ~30%
yield. The reaction was carried out with an excess of the
corresponding amine in CHCl3 in the presence of K2CO3. As
follows from the structure of the products obtained, the first
stage of the reaction apparently involves the conversion of
N-chloroalkylamines 3 into aldimines 9 as a result of E2 elimi-
nation of HCl (by analogy with reactions reported in ref. 6) in
the presence of a base; compounds 9 are hydrolysed into
corresponding aldehydes 10. The latter react with unreacted
N-chloroalkylamine 3 and excess amine to give diaziridines
2b,c and 1a (Scheme 3). In this case, a prerequisite for this
process to occur successfully is that the reaction mixture must
contain a small amount of water, which apparently participates
both in the first stage of the reaction, that is, elimination of HCl
by the inorganic base, and in the second stage, viz., hydrolysis
of aldimines 9a–c.
Similar results were obtained in the reactions of N,N-dichloro-
alkylamines 7a–c with an excess of the corresponding amines
in CHCl3 in the presence of K2CO3. Apparently, in this case,
the presence of excess amine at the first step of the reaction
results in the disproportionation of N,N-dichloroalkylamines
7a–c to give N-monochloroalkylamines 3a–c,7,8 whereas the
subsequent process does not differ from their conversion to
1,2-dialkyl- 1 and 1,2,3-trialkyldiaziridines 2 discussed above
(Scheme 3). The yields of diaziridines 2b,c from N,N-dichloro-
alkylamines 7b,c were 40–60%, while that of diaziridine 1a
was about 20%. However, the latter reaction in the case of
dichloroamine 7b was found to give yet another type of diaziri-
dine, viz., 1-ethyl-3-methyldiaziridine 13b, in 5% yield. Apparently,
the conversion of N,N-dichloroamines 7 involves the elimina-
tion of HCl on treatment with a base to give N-chloroaldimine
11, the reaction of which with the corresponding amine via
N-chloroaminal 12 in the presence of a base gives 1,3-dialkyl-
diaziridine 13 (Scheme 3).
†
All new compounds gave satisfactory elemental analyses and their
structures were confirmed by IR, 1H and 13C NMR spectroscopy. IR
spectra were measured on a UR-20 spectrometer in thin films of pure
substances; 1H and 13C NMR spectra were recorded on a Bruker AM300
spectrometer (300 MHz for 1H NMR and 75.5 MHz for 13C NMR).
Initial 1,3,5-trialkylhexahydro-1,3,5-triazines 6 were prepared according
to the following methods: trimethyl- 6a,11 triethyl- 6b,12 and tripropyl- 6c.13
General procedure for the synthesis of 1,2-dialkyldiaziridines 1a–c from
1,3,5-trialkylhexahydro-1,3,5-triazines 6a–c and N-chloroalkylamines 3a–c
in CHCl3 in the presence of K2CO3. Finely powdered K2CO3 (20.7 g,
0.15 mol), a few drops of water and 0.05 mol of 1,3,5-trialkylhexahydro-
1,3,5-triazine 6 were added to a 10–12% solution of N-chloroalkylamine 3
(0.15 mol) in CHCl3 at 15 °C. The reaction mixture was kept for 48–60 h
at 15–18 °C and was stirred for 1 h every 6–8 h. The end of the reaction
was detected by the disappearance of signals of N-chloroamines 3 in
1H NMR spectra.13 The precipitate was filtered off and washed with 30–
50 ml of CHCl3. The yields of resulting diaziridines 1a–c were found by
iodometric titration: 45% for 1a, 66.5% for 1b and 60% for 1c. The pure
diaziridines were isolated by distillation at atmospheric (compound 1a)
or reduced pressure (compounds 1b,c). Their characteristics were
identical to published data for these compounds.14,15 The 13C NMR
spectra of compounds 1b,c were not described.
1
1,2-Diethyldiaziridine 1b: 13C NMR (CDCl3) d: 12.7 (q, MeCH2, J
125.8 Hz, 2J 3.2 Hz), 54.9 (t, CH2Me, 1J 135.2 Hz), 55.7 (t, Cring
1J 173.3 Hz).
,
1,2-Dipropyldiaziridine 1c: 13C NMR (CDCl3) d: 11.6 (MeCH2), 21.8
(MeCH2CH2), 56.6 (Me CH2CH), 63.0 (Cring).
General procedure for the synthesis of 1,2-dialkyldiaziridines 1a,b
from 1,3,5-trialkylhexahydro-1,3,5-triazines 6a,b and N-chloroalkylamines
3a,b in water. A freshly prepared 25% aqueous solution of NaOCl
(0.15 mol) with a 10–15% excess of NaOH was added dropwise to a
20–25% aqueous solution of an alkylamine (0.15 mol) at 0–5 °C with
vigorous stirring. The yields of N-chloroalkylamines 3a,b were deter-
mined by iodometric titration. Then, corresponding 1,3,5-trialkylhexa-
hydro-1,3,5-triazines 6a,b (0.05 mol) were added, and the reaction mix-
ture was kept for 48 h at 4–6 °C and for 12 h at 18–22 °C. The end of
the reaction was determined by the disappearance of N-chloroamines 3
according to UV spectra (lmax = 250 nm). The yields of diaziridines 1a,b
were found by iodometric titration to be 10.2% for 1a and 12% for 1b.
General procedure for the synthesis of diaziridines 1a and 2b,c from
N-chloroalkylamines 3a–c (or N,N-dichloroamines 7a–c) and primary
aliphatic amines in CHCl3. Finely powdered K2CO3 (20.7 g, 0.15 mol),
a few drops of water and 0.45 mol of a primary aliphatic amine were
added to a 10–12% solution of N-chloroalkylamine 3a–c (0.15 mol) (or
0.075 mol of N,N-dichloroamine 7a–c) in CHCl3 at 15 °C. The reaction
mixture was kept for 72 h at 15–18 °C with stirring for 1 h every 6–8 h.
The completion of the reaction was detected by the disappearance of the
1
signals of N-chloroamines 3 in H NMR spectra.13 The precipitate was
filtered off and washed with 30–50 ml of CHCl3. The yields of the
resulting diaziridines were found by iodometric titration: ~34% for 1a,
95% for 2b and 84.5% for 2c from N-chloroamines 3 and 24.3%, 42%
and 60%, respectively, from N,N-dichloroamines 7. The pure diaziridines
were isolated by distillation. Compound 1a was characterized in refs. 14
and 15; only bp has been published for compound 2b,16 whereas com-
pound 2c has not been described in the literature.
In order to confirm this assumption, we synthesised authentic
N-chloroaldimine 11b.§ For this purpose, a solution of N,N-di-
chloroamine 7b in CHCl3 was stirred in the presence of humid
K2CO3 followed by distillation of the resulting solution at room
1,2-Diethyl-3-methyldiaziridine 2b: bp 43–45 °C (20 Torr) (lit.,16 bp 43–
45 °C), nD20 1.4210. 1H NMR (CDCl3) d: 1.09 (t, 3H, MeCH2, 3J 7.0 Hz),
3
1.16 (t, 3H, MeCH2, 3J 7.0 Hz), 1.29 (d, 3H, Me–Cring, J 5.4 Hz), 2.37
1
2
3
temperature in vacuo. Compound 11b was detected by H and
(m, 2H, HaHbCN, ABX3 spectrum, ∆n 54 Hz, J –12 Hz, JAX 7.0 Hz,
3JBX 7.2 Hz), 2.45 (m, 2H, HaHbCN, ABX3 spectrum, ∆n 33 Hz, 2J
3
3
‡
–11.5 Hz, JAX 6.50 Hz, JBX 6.7 Hz), 2.57 (q, 1H, CHring
,
3J 5.4 Hz).
The values of Edecomp for N-chloroalkylamine 3a were obtained as the
13C NMR (CDCl3) d: 11.7 (q, Me–Cring, J 129 Hz, J 4.0 Hz), 13.1 (q,
slopes of straight lines in the Arrhenius coordinates. The reaction rate
constants were calculated by relating the initial rate of decomposition of
a compound to its initial concentration. The determination of the decom-
position rate was based on changes in the concentration of starting
compound 3a, which was measured by iodometric titration or by 1H NMR
spectroscopy in the temperature range from –18 to +35 °C in CHCl3 and
from –5 to +30 °C in water. All experimental data were processed by the
least-squares method. The Edecomp value for compound 3a in aqueous
solutions is 17.8 kcal mol–1 and the reaction is of the first order. In
chloroform, the Edecomp is 22 kcal mol–1 and the reaction is of zero order.
The formally estimated decomposition rate of compound 3a at 20 °C
in the aqueous medium is two orders of magnitude higher than that in
chloroform.
1
2
MeCH2, 1J 129 Hz), 13.6 (q, MeCH2, 1J 128 Hz), 45.9 (t, CH2N, 1J
131.0 Hz, 2J 3.3 Hz), 55.0 (t, CH2N, 1J 132.0 Hz, 2J 3.4 Hz), 60.0 (d, Cring
,
1J 170.0 Hz). IR (n/cm–1): 2972, 2936, 2872, 1452, 1400, 1380, 1344,
1280, 1216, 1180, 1104, 948, 756, 664.
1,2-Dipropyl-3-ethyldiaziridine 2c: bp 71–73.5 °C (12 Torr), nD20 1.4322.
1H NMR (CDCl3) d: 0.84 (t, 3H, MeCH2CH2N, 3J 7.3 Hz), 0.87 (t, 3H,
3
3
MeCH2CH2N, J 7.3 Hz), 0.99 (t, 3H, MeCH2–Cring, J –7.5 Hz), 1.51
(m, 6H, MeCH2CH2N, MeCH2–Cring), 2.33 (m, 5H, MeCH2CH2N, CHring).
13C NMR (CDCl3) d: 10.4 (MeCH–Cring), 11.4 (MeCH2CH2N), 11.5
(
MeCH2CH2N), 19.5 (CH2–Cring), 21.6 (MeCH2CH2N), 22.3 (MeCH2CH2N),
(CH2N), 63.2 (CH2N), 66.5 (Cring). IR (n/cm–1): 2968, 2856, 2788, 1676,
1448, 1380, 1344, 1276, 1228, 1160, 1052, 972, 928, 756, 664.
Mendeleev Commun. 2005 117