Alkylammonium and alkylimidazolium perhaloborates, phosphates, and aluminates as catalysts in the Biginelli reaction

Article abstract of DOI:10.1007/s11178-005-0196-9

Tri- and tetraalkylammonium, 1,3-dialkylimidazolium, and 1,2,3-trialkylimidazolium salts with BF ₄ ^- , PF ₆ ^- , AlCl ₄ ^- , and Al ₂Cl ₇ ^- as counterions catalyze the Biginelli reaction, ensuring preparation of various 3,4-dihydropyrimidin-2(1H)-one and 3,4-dihydropyrimidine-2(1H)-thione derivatives in high yields in the absence of a solvent.

Full text of DOI:10.1007/s11178-005-0196-9

Russian Journal of Organic Chemistry, Vol. 41, No. 4, 2005, pp. 512–516. Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 4, 2005,
pp. 524–528.
Original Russian Text Copyright © 2005 by Putilova, Kryshtal’, Zhdankina, Troitskii, Zlotin.
Alkylammonium and Alkylimidazolium Perhaloborates,
Phosphates, and Aluminates as Catalysts in the Biginelli Reaction
E. S. Putilova, G. V. Kryshtal’, G. M. Zhdankina, N. A. Troitskii, and S. G. Zlotin
Zelinskii Institute of Organic Chemistry, Leninskii pr. 47, Moscow, 119991 Russia
e-mail: zlotin@ioc.ac.ru
Received May 18, 2004
Abstract—Tri- and tetraalkylammonium, 1,3-dialkylimidazolium, and 1,2,3-trialkylimidazolium salts with
BF4–, PF6–, AlCl4–, and Al2Cl7– as counterions catalyze the Biginelli reaction, ensuring preparation of various
3,4-dihydropyrimidin-2(1H)-one and 3,4-dihydropyrimidine-2(1H)-thione derivatives in high yields in the
absence of a solvent.
In the recent years, some 3,4-dihydropyrimidin-2
(1H)-one derivatives were found to exhibit biological
activity, in particular hypotensive [1] and antitumor
[2], as well as to act as selective α1a adrenoreceptor
antagonists [3]. Some alkaloids isolated from marine
algae contain a 3,4-dihydropyrimidin-2(1H)-one frag-
ment [4]. One of the most efficient methods for the
synthesis of 3,4-dihydropyrimidin-2(1H)-ones is one-
step three-component condensation of β-dicarbonyl
compounds with aldehydes and urea or thiourea deriv-
atives, which was discovered by P. Biginelli as early as
1893 [5]. This reaction is usually performed in an
organic solvent (alcohol or THF) in the presence of
a catalytic amount of a mineral [6] or Lewis acid [7].
Peng and Deng [8] recently described a procedure
for the preparation of 3,4-dihydropyrimidin-2(1H)-
ones from the same acyclic precursors without a sol-
vent using ionic liquids as catalysts, specifically
1-butyl-3-methylimidazolium tetrafluoroborate (I) and
hexafluorophosphate(V) (II). 1-Butyl-3-methylimida-
zolium chloride [BMIm][Cl] turned out to be less
active, while tetrabutylammonium chloride [Bu4N][Cl]
showed no catalytic activity [8].
reproduced the experimental conditions described in
[8], i.e., catalysis of the Biginelli reaction by liquid
salts I and II.
Triethylammonium salts III and IV were prepared
by mixing equimolar amounts of triethylamine and
tetrafluoroboric and hexafluorophosphoric acid,
respectively, in methylene chloride. Tetrabutylammo-
nium hexafluorophosphate(V) (V) was synthesized by
anion exchange reaction between tetrabutylammonium
bromide and hexafluorophosphoric acid in water;
poorly soluble salt V separated from the solution.
Benzyltriethylammonium chloroaluminates VII and
VIII were obtained by fusion of benzyltriethylam-
monium chloride with 1 or 2 equiv of anhydrous
aluminum chloride, respectively.
It should be noted that, although salts III–V, VII,
and VIII have been widely used previously as catalysts
and electrolytes (see, e.g., [9–13]), we have found no
published data on their preparation and physical and
spectral properties.
A
Et3NH A–
Bu4N PF6
N
N
Me
Bu
In order to elucidate the nature of the catalytic
activity of quaternary ammonium salts and the scope
of their application as catalysts in the Biginelli reaction
under solvent-free conditions, we examined the cata-
lytic activity of salts III–X consisting of alkylammo-
nium or alkylimidazolium cation and the following
anions: BF4–, PF6–, AlCl4–, and Al2Cl7–. Salts III–X
having bulky organic cations were selected due to their
low melting points and good solubility in molten
initial compounds. For the sake of comparison, we also
I, II, IX, X
III, IV
V
NEt3
A
PF6
N
N
Me
Bu
Me
VI
VII, VIII
I, III, A = BF4; II, IV, A = PF6; VII, IX, A = AlCl4;
VIII, X, A = Al2Cl7.
1070-4280/05/4104-0512 © 2005 Pleiades Publishing, Inc.

ALKYLAMMONIUM AND ALKYLIMIDAZOLIUM PERHALOBORATES, PHOSPHATES
513
As model reaction we studied the condensation of
acetylacetone with benzaldehyde and urea. The reac-
tions were carried out by fusion equimolar amounts of
the initial reactants and 0.6 mol % of salt I–X (or
without catalyst) at 120°C over a period of 1 h. The
yields of 5-acetyl-4-methyl-6-phenyl-3,4-dihydropyri-
midin-2(1H)-one (XIa) (after recrystallization from
80% isopropyl alcohol) in the reactions of acetyl-
acetone with benzaldehyde and urea in the presence of
salts I–X are given below.
corresponds to an analytically pure sample (after re-
crystallization from isopropyl alcohol), while the yield
given in [8], to the crude product.
Ionic catalytic systems based on tri- and tetra-
alkylammonium cations and/or chloroaluminate anions
are more advantageous than salts I and II due to their
simple preparation and low costs of the initial com-
pounds.
Salts III, IV, IX, and X were also used as catalysts
in the syntheses of 3,4-dihydropyrimidin-2(1H)-ones
XIb–XIn from various β-dicarbonyl compounds, alde-
hydes, and urea or thiourea in the absence of a solvent
(see table). Both linear and cyclic β-dicarbonyl com-
pounds and aromatic aldehydes with various substit-
uents in the aromatic ring were involved. Higher yields
of the condensation products from aromatic aldehydes
were obtained in the presence of salts III and IV with
perfluorinated anions, while the condensation with
readily oxidizable aldehydes of the thiophene series
was more effective in the presence of chloroaluminate
salts IX and X. As a rule, the yields of compounds XI
were somewhat lower than those obtained in an or-
ganic solvent [see, e.g., the data for XIb, XIc, XIi,
and XIj). On the other hand, this loss in the yield is
compensated by the simple experimental procedure
and easy isolation of the products.
O
O
O
+
PhCHO
+
Me
Me
H2N
Ph
NH2
O
I–X, 0.6 mol %
120°C, 1 h
Me
NH
Me
N
H
O
XIa
Catalyst
Yield, %
–
0
I
II III IV
V VI VII VIII IX X
70a 85 80 88 50 86 67 66 75 78
a
Yield 99% [8].
These data indicate that in all cases addition of
salts I–X to the reaction mixture ensures formation of
condensation product XIa. The catalytic activity of
triethylammonium tetrafluoroborate (III) and hexa-
fluorophosphate(V) (IV) somewhat exceeds the activ-
ity of 1,3-dialkylimidazolium salts I and II with the
corresponding perfluorinated anions. A high yield of
compound XIa (86%) was also obtained under catal-
ysis by 1,2,3-trialkylimidazolium hexafluorophos-
phate(V) (VI). Benzyltriethylammonium chloroalumi-
nates VII and VIII and 1-butyl-3-methylimidazolium
chloroaluminates IX and X also turned out to be good
catalysts in the Biginelli reaction. Using these salts, we
succeeded in obtaining compound XIa containing no
colored impurities typical of condensation products
formed in the presence of fluorine-containing salts.
The yield of XIa was slightly greater in the presence of
imidazolium chloroaluminates IX and X, and it almost
did not depend on the anion (AlCl4– or Al2Cl7–). Tetra-
butylammonium hexafluorophosphate(V) (V) was the
least active catalyst in the reaction under study: the
yield of XIa was as low as 50%.
Salts III, IV, IX, and X were ineffective in con-
densations involving aliphatic aldehydes or N-alkyl-
ureas. These reactions were not selective, and they
resulted in formation of complex mixtures of products.
Presumably, the catalytic activity of salts I–X origi-
nates from their ability to release the corresponding
hydrogen halides. It is known that chloroaluminates
VII–X are hydrolytically unstable: in the presence of
atmospheric moisture they decompose with elimina-
tion of hydrogen chloride [12–14]. Alkylimidazolium
tetrafluoroborates and hexafluorophosphates(V) are
more resistant to hydrolysis, but they gradually release
HF on heating in the presence of traces of water [14].
Probably, tetrabutylammonium hexafluorophosphate(V)
(V) is also capable of undergoing hydrolysis at
elevated temperature. Triethylammonium salts III and
IV are comparable to chloroaluminates VII–X in hy-
drolytic stability: on exposure to air they release HF
even at room temperature (a peace of litmus paper
turns red when placed over the surface of solid salt).
The yield of compound XIa obtained in the
presence of salt I under the conditions reported in [8]
was 70% against 99% given in [8]. Presumably, the
reason for the observed difference is that our yield
Trace amounts of hydrogen halides present in the
reaction mixture are likely to initiate the Biginelli reac-
tion [6]. Water liberated during the process accelerates
hydrolysis of the catalyst, and the reaction becomes
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 4 2005

PUTILOVA et al.
514
Condensation of β-dicarbonyl compounds with aldehydes and urea (thiourea) in the presence of salts III, IV, IX, and X
O
R3
Catalyst, 0.6 mol %
120–125°C, 1 h
O
O
X
R2
R1
NH
R1
+
R3CHO
+
R2
H2N
NH2
N
H
X
XIa–XIn
Comp.
no.
R1
R2
R3
X
Catalyst
Yield,a %
88
80 (85[15]b)
mp., °C
Me
Me
Me
Me
Ph
Ph
O
S
235–236 (233–236 [7])
220–224 (220–221 [15])
267–269 (268–270 [16])
207–209
XIa
XIb
XIc
XId
H
H
H
H
IV
X
3-O2NC6H4
4-O2NC6H4
O
S
86 (92 [16]b)
IV
IV
IX
IV
X
74
70
Me
Me
Me
4-ClC6H4
4-FC6H4
86
189–191
209–212
XIe
XIf
H
H
S
S
74
89
IV
IX
X
72
H
H
H
H
2-Thienyl
Ph
O
O
S
80
230–232
XIg
XIh
XIi
OMe
OMe
OMe
78 (92 [17]b)
83 (91 [15]b)
80
212–214 (209–212 [18])
202–204 (201–202 [15])
239–242
IX
IV
IX
Ph
2-Thienyl
O
XIj
OMe
2-Thienyl
72
226–227
XIk
H
S
IV
IX
III
III
IV
84
Ph
S
S
70 (56 [18]b)
282–285 (281–282 [19]b)
279–282
XIl
–CMe2CH2–
–CMe2CH2–
–CMe2CH2–
4-O2NC6H4
2-Thienyl
68
65
XIm
XIn
O
285–287
a
After recrystallization from 80% aqueous isopropyl alcohol.
The reaction was carried out in ethanol.
b
autocatalytic. Gradual increase in the concentration of
protons improves the selectivity of the condensation
and the yield. When the reaction was performed
without a solvent in the presence of a catalytic amount
of concentrated hydrochloric acid, i.e., in a relatively
strongly acidic medium at the initial stage, the process
was accompanied by tarring.
EXPERIMENTAL
1
The H NMR spectra were recorded on a Bruker
WM-250 instrument (250.3 MHz). The elemental
composition were determined on a Perkin–Elmer 2400
analyzer. Alkylimidazolium salts I [20], II [21], and
VI [22] were synthesized by known methods.
We can conclude that alkylammonium and alkyl-
imidazolium salts with BF4–, PF6–, AlCl4–, and Al2Cl7–
anions may be regarded as general catalysts in the
Biginelli reaction, which are characterized by a com-
mon mechanism of the catalytic action. The use of
these catalysts ensures preparation of a wide series of
3,4-dihydropirimidin-2(1H)-ones and -thiones in high
yields under simple experimental conditions requiring
no organic solvent.
Triethylammonium tetrafluoroborate (III). To
a solution of 13.9 ml (0.10 mol) of triethylamine in
50 ml of methylene chloride we added dropwise at 0°C
under vigorous stirring 18 ml (0.10 mol) of a 50%
aqueous solution of HBF4. The mixture was stirred for
15–20 min at 20°C, a saturated aqueous solution of
sodium chloride was added, and the organic phase was
separated, dried over MgSO4, and evaporated under
reduced pressure. Yield 7.56 g (40%), mp 58–62°C.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 4 2005

ALKYLAMMONIUM AND ALKYLIMIDAZOLIUM PERHALOBORATES, PHOSPHATES
515
1H NMR spectrum (acetone-d6), δ, ppm: 8.80 br.s
(1H), 3.35 m (6H), 1.35 t (9H, J = 7.5 Hz). Found, %:
C 38.1; H 8.5; F 40.2; N 7.4. C6H16BF4N. Calculated,
%: C 38.12; H 8.55; F 40.2; N 7.41.
3.0 mmol of aldehyde, 3.0 mmol of urea or thio-
urea, and 0.018 mmol of salt I–X was thoroughly
stirred and was heated for 1 h at 120–125°C. It was
then cooled to room temperature, and the resulting
crystalline product was washed in succession with
hot water (2×4 ml), methylene chloride (2×4 ml),
and diethyl ether (3 ml) and recrystallized from
2-propanol–water (4:1). The yields and melting
points of compounds XIa–XIn are given in table.
Triethylammonium hexafluorophosphate(V)
(IV) was synthesized in a similar way using 24 ml
(0.10 mol) of a 60% aqueous solution of HPF6. Yield
1
16.2 g (70%), mp 72–74°C. H NMR spectrum
(acetone-d6), δ, ppm: 8.00 br.s (1H), 3.40 m (6H),
1.40 t (9H, J = 7.5 Hz). Found, %: C 29.2; H 6.5;
F 46.1; N 5.7. C6H16F6NP. Calculated, %: C 29.16;
H 6.52; F 46.12; N 5.67.
5-Acetyl-6-methyl-4-(4-nitrophenyl)-3,4-di-
1
hydropyrimidine-2(1H)-thione (XId). H NMR
spectrum (DMSO-d6), δ, ppm: 10.35 s (NH, 1H),
9.75 s (NH, 1H), 8.20 d (2H, J = 7.5 Hz), 7.55 d
(2H, J = 7.5 Hz), 5.40 d (1H, J = 7.4 Hz), 2.35 s
(3H), 2.25 s (3H). Found, %: C 53.6; H 4.5; N 14.4;
S 11.1. C13H13N3O3S. Calculated, %: C 53.64;
H 4.47; N 14.42; S 11.01.
Tetrabutylammonium hexafluorophosphate(V)
(V). To a solution of 6.44 g (0.02 mol) of tetrabutyl-
ammonium bromide in 30 ml of water we added drop-
wise at 0°C under vigorous stirring 4.8 ml (0.02 mol)
of a 60% aqueous solution of HPF6. The mixture was
stirred for 15–20 min at 20°C, 25 ml of chloroform
was added, and the organic phase was separated,
washed with water (2×10 ml), dried over MgSO4, and
evaporated under reduced pressure. Yield 7.0 g (90%),
5-Acetyl-4-(4-chlorophenyl)-6-methyl-3,4-di-
1
hydropyrimidine-2(1H)-thione (XIe). H NMR
spectrum (DMSO-d6), δ, ppm: 10.25 s (NH, 1H),
9.65 s (NH, 1H), 7.45 d (2H, J = 7.5 Hz), 7.20 d
(2H, J = 7.5 Hz), 5.25 d (1H, J = 7.6 Hz), 2.35 s
(3H), 2.25 s (3H). Found, %: C 55.6; H 4.7; N 10.0;
S 12.6. C13H13ClN2OS. Calculated, %: C 55.63;
H 4.71; N 10.02; S 12.58.
1
mp 243–246°C. H NMR spectrum (DMSO-d6), δ,
ppm: 3.15 m (8H), 1.60 m (8H), 1.35 m (8H), 1.00 t
(12H). Found, %: C 49.6; H 9.4; F 29.4; N 3.6.
C16H36F6NP. Calculated, %: C 49.6; H 9.37; F 29.42;
N 3.62.
5-Acetyl-4-(4-fluorophenyl)-6-methyl-3,4-di-
1
Benzyltriethylammonium tetrachloroaluminate
(VII). A flask was dried, purged with argon, and
charged with 1.14 g (5.0 mmol) of benzyltriethyl-
ammonium chloride, and 0.67 g (5.0 mmol) of AlCl3
was slowly added at 20°C under stirring in a weak
stream of argon. The mixture was then stirred for 2–3 h
at 80–90°C (until it became homogeneous) and cooled
to room temperature. Yield 1.60 g (90%), yellowish
hydropyrimidine-2(1H)-thione (XIf). H NMR
spectrum (DMSO-d6), δ, ppm: 10.20 s (NH, 1H),
9.65 s (NH, 1H), 7.20–7.45 m (4H), 5.31 d (1H,
J = 6.5 Hz), 2.35 s (3H), 2.25 s (3H). Found, %:
C 59.1; H 5.0; N 10.6; S 12.1. C13H13FN2OS. Cal-
culated, %: C 59.09; H 5.01; N 10.62; S 12.11.
5-Acetyl-6-methyl-4-(2-thienyl)-3,4-dihydro-
1
1
pyrimidin-2(1H)-one (XIg). H NMR spectrum
hygroscopic crystals, mp 72.5–75°C. H NMR spec-
(DMSO-d6), δ, ppm: 9.03 s (NH, 1H), 7.75 s (NH,
1H), 7.20–6.85 m (3H), 5.42 d (1H, J = 6.4 Hz),
2.35 s (3H), 2.25 s (3H). Found, %: C 55.9; H 5.1;
N 11.9; S 13.6. C11H12N2O2S. Calculated, %:
C 55.91; H 5.09; N 11.88; S 13.64.
trum (DMSO-d6), δ, ppm: 7.50 m (5H), 4.55 s (2H),
3.25 d (6H, J = 7.6 Hz), 1.40 m (9H). Found, %:
C 43.2; H 6.1; Cl 39.3; N 3.9. C13H22AlCl4N. Calcu-
lated, %: C 43.23; H 6.15; Cl 39.26; N 3.88.
Benzyltriethylammonium heptachlorodialumi-
nate (VIII) was synthesized in a similar way using
excess AlCl3 (1.30 g, 10.0 mmol). Yield 2.30 g (98%),
yellowish hygroscopic crystals, mp 210–214°C.
1H NMR spectrum (DMSO-d6), δ, ppm: 7.50 m (5H),
4.55 s (2H), 3.25 (6H, J = 7.7 Hz,), 1.40 m (9H).
Found, %: C 31.6; H 4.5; Cl 50.2; N 2.8. C13H22Al2Cl7N.
Calculated, %: C 31.57; H 4.49; Cl 50.18; N 2.83.
Methyl 6-methyl-2-oxo-4-(2-thienyl)-1,2,3,4-
tetrahydropyrimidine-5-carboxylate (XIj).
1H NMR spectrum (DMSO-d6), δ, ppm: 9.03 s (NH,
1H), 7.75 s (NH, 1H), 7.20–6.85 m (3H), 5.42 d
(1H, J = 6.4 Hz), 3.60 s (3H), 2.25 s (3H). Found,
%: C 52.4; H 4.8; N 11.1; S 12.7. C11H12N2O3S.
Calculated, %: C 52.39; H 4.82; N 11.09; S 12.72.
Condensation of β-dicarbonyl compounds with
aldehydes and urea or thiourea (general procedure).
A mixture of 3.0 mmol of β-dicarbonyl compound,
Methyl 6-methyl-4-(2-thienyl)-2-thioxo-
1,2,3,4-tetrahydropyrimidine-5-carboxylate
(XIk). H NMR spectrum (DMSO-d6), δ, ppm:
1
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 41 No. 4 2005

PUTILOVA et al.
516
Leppert, P., Nagarathnam, D., and Forray, C., J. Med.
Chem., 2000, vol. 43, p. 2703.
10.25 s (NH, 1H), 9.55 s (NH, 1H), 7.20–6.85 m (3H),
5.42 d (1H, J = 6.4 Hz), 3.60 s (3H), 2.25 s (3H).
Found, %: C 49.2; H 4.5; N 10.4; S 23.9. C11H12N2O2S2.
Calculated, %: C 49.23; H 4.52; N 0.41; S 23.88.
4. Heys, L., Moore, C.G., and Murphy, P.J., Chem. Soc.
Rev., 2000, vol. 29, p. 57.
5. Biginelli, P., Gazz. Chim. Ital., 1893, vol. 23, p. 360.
6. Kappe, C.O., Acc. Chem. Res., 2000, vol. 33, p. 879.
7,7-Dimethyl-4-(4-nitrophenyl)-2-thioxo-
2,3,4,6,7,8-hexahydro-1H-quinazolin-5-one (XIm).
1H NMR spectrum (DMSO-d6), δ, ppm: 10.40 s (NH,
1H), 9.55 s (NH, 1H), 8.12 d (2H, J = 7.3 Hz), 7.65 d
(2H, J = 7.4 Hz), 5.35 d (1H, J = 7.4 Hz), 2.35 d (1H,
J = 16 Hz), 2.40 d (1H, J = 16 Hz), 2.10 d (1H, J =
15 Hz), 2.20 d (1H, J = 15 Hz), 1.15 s (3H), 0.9 s (3H).
Found, %: C 58.0; H 5.2; N 12.7; S 9.7. C16H17N3O3S.
Calculated, %: C 58.04; H 5.23; N 12.68; S 9.69.
7. Hu, E.H., Sidler, D.R., and Dolling, U.-H., J. Org.
Chem., 1998, vol. 63, p. 3454; Ma, Y., Qian, C.,
Wang, L., and Yang, M., J. Org. Chem., 2000, vol. 65,
p. 3864; Lu, J., Bai, Y., Wang, Z., Yang, B., and Ma, Y.,
Tetrahedron Lett., 2000, vol. 41, p. 9075; Ranu, B.C.,
Hajra, A., and Jana, U., J. Org. Chem., 2000, vol. 65,
p. 6270.
8. Peng, J. and Deng, Y., Tetrahedron Lett., 2001, vol. 42,
7,7-Dimethyl-4-(2-thienyl)-2-thioxo-2,3,4,6,7,8-
hexahydro-1H-quinazolin-5-one (XIn). H NMR
p. 5917.
1
9. Itoh, H., Kato, I., Unoura, K., and Senda, Y., Bull.
Chem. Soc. Jpn., 2001, vol. 74, p. 339.
spectrum (DMSO-d6), δ, ppm: 9.03 s (NH, 1H), 7.75 s
(NH, 1H), 7.20 s (1H,), 6.85 s (2H), 5.35 d (1H, J =
7.4 Hz), 2.35 d (1H, J = 16 Hz), 2.40 d (1H, J =
16 Hz), 2.10 d (1H, J = 15 Hz), 2.20 d (1H, J = 15 Hz),
1.15 s (3H), 0.90 s (3H). Found, %: C 60.8; H 5.8;
N 10.1; S 11.6. C14H18N2O2S. Calculated, %: C 60.78;
H 5.77; N 10.09; S 11.64.
10. Trost, B.M. and Kulawiec, R.J., J. Am. Chem. Soc.,
1993, vol. 115, p. 2027; Backwall, J.-E. and Andreas-
son, U., Tetrahedron Lett., 1993, vol. 34, p. 5459.
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vol. 124, p. 2528; Szumma, A. and Jurczak, J., Helv.
Chim. Acta, 2001, vol. 84, p. 3760.
12. Karataev, A.M., Malovichko, N.S., Kovalevskaya, L.I.,
Elagina, S.K., and Moshchinskaya, N.K., Vopr. Khim.
Khim. Tekhnol., 1974, vol. 33, p. 26.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 03-03-32659) and by the Russian Academy of
Sciences (Program of Fundamental Research of the
Presidium of the Russian Academy of Sciences).
13. Moshchinskaya, N.K. and Kovalevskaya, L.I., USSR
Inventor’s Certificate no. 547440, 1977; Chem. Abstr.,
1977, vol. 87, no. 40049.
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