Calcium hypochlorite as an efficient reagent for oxidation of urazoles under mild heterogeneous conditions

Full text of DOI:10.1023/B:RUJO.0000044562.96808.06

Russian Journal of Organic Chemistry, Vol. 40, No. 6, 2004, pp. 914–916. From Zhurnal Organicheskoi Khimii, Vol. 40, No. 6, 2004, pp. 950–952.
Original English Text Copyright © 2004 by Zolfigol, Mallakpour, Khazaiae, Vaghaie, Torabi.
SHORT
COMMUNICATIONS
Calcium Hypochlorite as an Efficient Reagent for Oxidation
of Urazoles under Mild Heterogeneous Conditions*
1
2
1
1
1
M. A. Zolfigol , Sh. Mallakpour , A. Khazaiae , R. G. Vaghaie , and M. Torabi
1
Chemistry Department, College of Science, Bu-Ali Sina University, Hamadan, 65174 Iran
e-mail: zolfi@basu.ac.ir
2
Organic Polymer Chemistry Research Laboratory, College of Chemistry, Isfahan University of Technology,
Isfahan, 84156 Iran
Received July 10, 2003
4
-Substituted 4,5-dihydro-3H-1,2,4-triazole-3,5-di-
conditions. Moreover, most of the reported reagents
produce by-products which either initiate decomposi-
tion of the sensitive dihydrotriazolediones or are dif-
ficult to remove from the latter. Another significant
drawback of the old procedures is the use of reagents
which either are highly toxic or produce serious dis-
posal problems (or both) [8]. We recently demon-
strated the remarkable convenience of using gaseous
N O generated in situ as a clean and efficient oxidant
ones attract interest due to their versatile reactivity and
ability to participate in such reactions as [4+2]- [1, 2]
and [2+2]-cycloadditions [3], ene reactions [4], elec-
trophilic aromatic substitution [5], dehydrogenation
6], and oxidation of alcohols to aldehydes and ketones
7]. On the other hand, their unusual reactivity makes
[
[
them difficult to prepare and purify. For example,
-phenyl-4,5-dihydro-3H-1,2,4-triazole-3,5-dione (IIe)
4
2
4
is an extremely reactive dienophile and enophile which
is at least 1000 times more reactive than tetracyano-
ethylene in the Diels–Alder reaction with 2-chloro-
butadiene and 2000 times more reactive than maleic
anhydride [1]. All known methods of synthesis of
these compounds require oxidation of the correspond-
ing 1,2,4-triazolidine-3,5-diones I and III which are
more commonly known as urazoles.
for the above purpose [1, 10, 11]. It is known that
gaseous N O is corrosive and highly toxic and that
2
4
it must be generated under an effective hood with
caution. Therefore, we decided to develop a new
reagent or reagent system to overcome the above
limitations and provide a clean and easy work-up.
Heterogeneous reagent systems [19] offer many advan-
tages such as simple experimental procedure, mild
reaction conditions, and minimization of chemical
wastes as compared to reactions in solution. We have
Although a wide variety of reagents are capable of
effecting oxidation of urazoles [8–18], this trans-
formation remains capricious because the initial com-
pounds are very sensitive to the oxidant and reaction
examined a number of heterogeneous reagent systems
+
based on generation in situ of HNO (NO ) [12] or
2
Scheme 2.
Scheme 1.
R1
R1
Ca(OCl) , CH Cl ,
2
2
2
HN
N
N
N
HN
N
N
N
room temperature
O
O
N
X
N
O
O
O
O
N
X
O
O
Ca(OCl) , CH Cl ,
room temperature
O
N
O
O
N
O
2
2
2
R2
R2
N
Ia–Ii
IIa–IIi
HN
N
N
N
1
2
I, II, R = H, R = Me (a), Et (b), Bu (d), cyclohexyl (e),
R3
1
Ph (f), 4-ClC
6
H
4
(g), 4-O
2 6 4 2 6 4
NC H (h), 3,4-Cl C H (i); R =
IIIa, IIIb
IVa, IVb
2
Na, R = Pr (c).
1
3
1
3
III, IV, R = R = Na; X = (CH
2
)
6
(a); R = R = H,
*
The original article was submitted in English.
X = 4-C CH C H -4 (b).
6
H
4
2 6 4
1
070-4280/04/4006-0914 © 2004 MAIK “Nauka/Interperiodica”

CALCIUM HYPOCHLORITE AS AN EFFICIENT REAGENT
915
2
Oxidation of urazoles I and bis-urazoles III to the corresponding dihydrotriazolediones II and IV with Ca(OCl) in
methylene chloride at room temperature.
mp, °C
Initial
comp. no.
a
Oxidant-to-substrate
ratio, mmol
b
Product
Time, min
Yield, %
found
reported
c
c
c
c
Ia
IIa [8]
2
2
2
2
2
2
2
4
2
2
2
15
15
15
15
15
15
15
45
15
20
30
100
100
082
085
095
092
098
070
090
098
075
097–99
054–56
042–44
042–45
097–98
168–175
134–135
125–126
110–113
145–150
182–185
098–98.5 [8]
053 [15]
Ib
Ic
IIb [15]
IIc [11, 15]
IId [8]
044 [11]
Id
Ie
044–44.5 [8]
095–96 [8]
IIe [8]
If
IIf [8, 10]
IIg [8]
170–178 [10]
130–132 [8]
128–129 [17]
113–115 [14]
146–149 [17]
Ig
Ih
Ii
IIh [8,17]
IIi [14]
IIIa
IIIb
IVa [17]
IVb [17]
d
d
185 [17]
a
b
c
d
All the isolated products are known compounds; their spectral parameters and physical constants have been reported in the literature.
Yields of the isolated products.
Conversion.
With decomposition.
+
H O (Cl ) [13]. As a result, we have developed
identified by com-paring their spectral parameters (IR,
2
2
1
13
a simple, cheap, and convenient method for effective
conversion of urazoles I and bis-urazoles III to the
corresponding dihydrotriazolediones II and IV using
calcium hypochlorite under heterogeneous conditions
UV, and H and C NMR) and physical constants
with those of authentic samples. 4,5-Dihydro-3H-1,2,4-
triazole-3,5-diones are sensitive to light, heat, alcohols,
ethers, transition metals, and any nucleophiles. In addi-
tion, they are very volatile; therefore, the solvent must
be removed at a temperature not exceeding 50°C to
avoid loss of the target product. From this viewpoint,
methylene chloride is the best solvent.
(
Schemes 1, 2).
Different urazoles and bis-urazoles were subjected
to oxidation in the presence of Ca(OCl) in methylene
2
chloride. The reactions were performed under mild
conditions at room temperature with excellent yields.
The products, dihydrotriazolediones II or bis-dihydro-
triazolediones IV can be isolated by simple filtration
of the reaction mixture, followed by removal of the
solvent from the filtrate. The results and reaction
conditions are given in table.
Chemicals were purchased from Fluka, Merck,
Riedel–Dehaen AG, and Aldrich chemical companies.
All urazoles and bis-urazoles were synthesized by the
procedures reported previously [1, 4, 5, 10, 11].
The authors are grateful to the Research Council of
Bu-Ali Sina University, Hamadan, Iran, and Isfahan
University of Technology, Isfahan, Iran, for financial
support.
Oxidation of 4-cyclohexylurazole (Ie) to 4-cyclo-
hexyl-4,5-dihydro-3H-1,2,4-triazole-3,5-dione (IIe)
with Ca(ClO) . A mixture of 0.366 g (2.0 mmol) of
2
compound Ie and 0.568 g (4 mmol) of Ca(ClO) in
2
REFERENCES
2
0 ml of methylene chloride was stirred for 15 min at
room temperature. The mixture was filtered, and the
solvent was distilled off from the filtrate on a water
bath (40–50°C). Yield 0.290 g (95%); red crystals,
1
. Mallakpour, S.E. and Zolfigol, M.A., Indian J. Chem.,
Sect. B, 1995, vol. 34, p. 183 (see also references
therein); Mallakpour, S.E. and Zolfigol, M.A., Indian J.
Chem., Sect. B, 1995, vol. 34, p. 302; Mallakpour, S.E.
and Zolfigol, M.A., Indian J. Chem., Sect. B, 1998,
vol. 37, p. 1001; Mallakpour, S.E. and Zolfigol, M.A.,
Indian J. Chem., Sect. B., 1999, vol. 38, p. 777.
mp 95–98°C; published data [8]: mp 95–96°C.
1
H NMR spectrum (90 MHz, CDCl , TMS), δ, ppm:
3
1
3
3
.90 quint (1H), 1.82–1.26 m (10H). C NMR spec-
trum (CDCl , TMS), δ , ppm: 158.77, 53.93, 28.72.
3
C
24.96, 24.28. Compounds IIa–IId and IIf–IIi were
2. Desimoni, G., Faita, G., Righetti. P.P., Sulcini, A., and
synthesized in a similar way. The products were
Tsyganov, D., Tetrahedron, 1994, vol. 50, p. 1821.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 6 2004

9
16
ZOLFIGOL et al.
10. Mallakpour, S.E., J. Chem. Educ., 1992, vol. 69, p. 238.
3
4
5
. Hall, J.H. and Krishnan, G., J. Org. Chem., 1984, vol. 49,
p. 2498; Hall, J.H. and Jones, M.L., J. Org. Chem., 1983,
vol. 48, p. 822; Seymour, G.A. and Green, F.D., J. Am.
Chem. Soc., 1980, vol. 102, p. 6384.
1
1. Mallakpour, S.E. and Zolfigol, M.A., J. Sci. I. R. Iran,
993, vol. 4, p. 199.
1
1
2. Zolfigol, M.A., Torabi, M., and Mallakpour, S.E.,
Tetrahedron, 2001, vol. 57, p. 8381 (see also our
references therein).
. Mallakpour, S.E., Butler, G.B., Aghabozorg, H., and
Palanik, G., Macromolecules, 1985, vol. 18, p. 342;
Lai, Y.C., Mallakpour, S.E., Butler, G.B., and Pala-
nik, G., J. Org. Chem., 1985, vol. 50, p. 4378.
. Mallakpour, S.E. and Butler, G.B., J. Polym. Sci.,
Part A: Polym. Chem., 1989, vol. 27, p. 217; Mallak-
pour, S.E. and Butler, G.B., J. Polym. Sci., Part A:
Polym. Chem., 1989, vol. 27, p. 125; Mallakpour, S.E.
and Butler, G.B., J. Polym. Sci., Part A: Polym. Chem.,
1
3. Zolfigol, M.A., Bagherzadeh, M., Chehardoli, G.A.,
Mallakpour, S.E., and Mamaghani, M., J. Chem. Res.,
Synop., 2001, p. 390.
1
1
1
4. Wamhoff, H. and Wald, K., Org. Prep. Proced. Int.,
1
975, vol. 7, p. 251.
5. Arya, V.P. and Shenoy, S.J., Indian J. Chem., Sect. B,
976, vol. 14, p. 883.
1
1
987, vol. 25, p. 2781.
6. Burrage, M.E., Cookson, R.C., Gupte, S.S., and
Stevens, I.D.R., J. Chem. Soc., Perkin Trans. 1, 1975,
p. 1325.
6
7
. Klindert, T. and Seitz, G., Synth. Commun., 1996,
vol. 26, p. 2587 (see also references therein).
. Cookson, R.C., Stevens, I.D.R., and Watts, C.T.,
J. Chem. Soc., Chem. Commun., 1966, p. 744; Borha-
ni, D.W. and Green, F.D., J. Org. Chem., 1986, vol. 51,
p. 1563; Akasaka, T., Sonobe, H., Sato, R., and
Ando, W., Tetrahedron Lett., 1984, vol. 25, p. 4757.
17. Mallakpour, S.E. and Butler, G.B., Advances in Polymer
Synthesis, Culbertson, B.M. and McGrath, J.E., Eds.,
New York: Plenum, 1985, Polymer Science and Tech-
nology Series, vol 31, pp. 1–25.
8
9
. Stickler, J.C. and Pirkle, W.H., J. Org. Chem., 1966,
vol. 31, p. 3444.
. Read, G. and Richardson, N.R., J. Chem. Soc., Perkin
Trans. 1, 1996, p. 167.
18. Zolfigol, M.A., Zebarjadian, M.H., Chehardoli, G., Mal-
lakpour, S.E., ad Shamsipur, M., Tetrahedron, 2001,
vol. 57, p. 1627.
19. Zolfigol, M.A., Tetrahedron, 2001, vol. 57, p. 9509.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 6 2004