668
KASHPAROVA et al.
dine-2-oxyl VII (cf. IV and V). Probably, the reaction
pathway depends on the basicity of the initial sub-
stances. With I, elimination of N2 and HX is the pre-
vailing process.
the solvent, 0.9 g (12%) of VI was obtained; mp 34
35 C (cf. mp 33 C [3]). The insoluble product VII
was purified by column chromatography (l = 50 cm,
r = 1.5 cm, sorbent Al2O3, Brockmann grade II, elu-
ent CH2Cl2). Yield of VII 6.8 g (80%). The mixing
test with an authentic sample gives no depression of
the melting point [3].
When diazotization of I is performed in glacial
acetic acid, the only reaction product is 4-acetylami-
no-2,2,6,6-tetramethylpiperidine VIII. Compound II
is also acylated with glacial acetic acid at room tem-
perature; the yield of 4-acetylamino-2,2,6,6-tetrameth-
ylpiperidine-1-oxyl IX is 95%. According to [5],
2,2,6,6-tetramethylpiperidine derivatives are only acyl-
ated with acetic anhydride.
4-Acetylamino-2,2,6,6-tetramethylpiperidine-1-
oxyl IX. To 30 ml of glacial acetic acid, we added
with stirring 2.6 g (0.015 mol) of radical II. The stir-
ring was continued for 1 h, after which the mixture
was alkalized with a KOH solution to pH 10 11 and
extracted with methylene chloride (3 30 ml). The or-
ganic extracts were combined and dried over Na2SO4;
the solvent was removed. The remaining red-orange
crystalline compound IX (3.3 g, 95%) was recrystal-
lized from water; mp 145 146 C. The compound was
identified by a mixing test with an authentic sample
and by comparison of the IR spectra [3].
EXPERIMENTAL
2,2,6,6-Tetramethyl-1,2,5,6-tetrahydropyridine
III and 4-chloro-2,2,6,6-tetramethylpiperidine IV.
To a solution of 7.8 g (0.05 mol) of amine I in 10 ml
1
of water, 9 ml of HCl ( = 1.19 g ml ) was added.
Then, a solution of 5.2 g (0.075 mol) of NaNO2 in
10 ml of water was added dropwise with stirring. In
the course of the reaction, the pH was maintained
within 3 5 by adding aqueous HCl (1 : 1). After the
reaction was complete, the mixture was alkalized first
with K2CO3 and then with KOH to pH 10 12, after
which it was extracted with benzene (3 10 ml).
The benzene extracts were combined, the solvent was
evaporated, and the residue was distilled under atmo-
spheric pressure. Yield of III 5.5 g (80%), bp 143
145 C (cf. bp 145 146 C [3]). The residue was re-
crystallized from methanol. Yield of colorless crystal-
line compound IV 0.9 g (10%), mp 37 38 C; the
compound was identified using a mixing test with
an authentic sample [6].
CONCLUSIONS
(1) Diazotization of 4-amino-2,2,6,6-tetramethyl-
piperidine in HCl, HBr, H2SO4, and dilute AcOH
affords 2,2,6,6-tetramethyl-1,2,5,6-tetrahydropyridine
in 80 90% yield.
(2) Diazotization of 4-amino-2,2,6,6-tetramethyl-
piperidine-1-oxyl in 30% AcOH gives 4-hydroxy-
2,2,6,6-tetramethylpiperidine-1-oxyl in 80% yield.
(3) In glacial AcOH, 4-amino-2,2,6,6-tetramethyl-
piperidine and the corresponding radical are converted
virtually completely to the corresponding N-acetyl
derivatives.
When the reaction was performed in HBr, the yield
of III was 80%, and that of 4-bromo derivative V,
10%; mp 43 45 C (from methanol; cf. mp 44 45 C
[6]).
REFERENCES
1. Dagonneau, M., Ivanov, V.B., Rozantsev, E.G., et al.,
J. Macromol. Sci., 1982 1983, no. 2, pp. 169 202.
2. Rozantsev, E.G., Sholle, V.D., Ivanov, V.B., et al.,
in Polymer Stabilization and Degradation, Washington
DC: Am. Chem. Soc., 1985, pp. 11 37.
2,2,6,6-Tetramethyl-1,2,5,6-tetrahydropyridine-
1-oxyl VI and 4-hydroxy-2,2,6,6-tetramethylpiperi-
dine-1-oxyl VII. To a solution of 8.5 g (0.05 mol) of
II in 40 ml of distilled water, 20 ml of glacial acetic
acid was added, the mixture was cooled to 5 C, and
a solution of 6.4 g (0.075 mol) of NaNO2 in 20 ml of
water was gradually added. The resulting mixture was
stirred for 2 h, alkalized with a KOH solution to pH
10 11, and extracted with benzene (3 50 ml). The
benzene extracts were combined, the solvent was
removed, and the residue was treated with hexane
(50 ml). Compound VI passed into hexane, and com-
pound VII remained in the residue. After removal of
3. Rozantsev, E.G., Svobodnye iminoksil’nye radikaly
(Free Iminoxyl Radicals), Moscow: Khimiya, 1970.
4. Avrutskaya, I.A., Kagan, E.Sh., Smirnov, V.A., and
Fioshin, M.Ya., Nitroksil’nye radikaly: sintez, khimiya i
prilozheniya (Nitroxyl radicals: Synthesis, Chemistry,
and Applications), Moscow: Nauka, 1987.
5. Dagonneau, M., Sholle, V.D., Rozantsev, E.G., et al.,
Synthesis, 1984, no. 11, pp. 895 916.
6. Rozantsev, E.G., Golubev, V.A., and Neiman, M.B.,
Izv. Akad. Nauk SSSR, Ser. Khim., 1965, no. 2,
pp. 391 393.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 4 2002