Two approaches to the transformation of (benzimidazol-2-ylmethyl)triphenylphosphonium chloride into the derivatives of pyrimido[1,6-a]benzimidazole

Article abstract of DOI:10.1023/A:1023328910321

The reaction of readily accessible (benzimidazol-2-ylmethyl)triphenylphosphonium chloride with acyl isothiocyanates in the presence of triethylamine, as well as consecutive treatment of the above phosphonium salt first with N,N-dimethylformamide dimethyl acetal and then with phenyl or allyl isothiocyanate gives two types of phosphorus-containing derivatives of pyrimido[1,6-a]benzimidazole with the thione group in position 3 or 1 of the condensed system. The structure of one of compounds of the first type, 3-thioxo-1-p-tolyl-3,4-dihydropyrimido[1,6-a] benzimidazol-4-ylidenetriphenylphosphorane, was determined by single crystal X-ray diffraction.

Full text of DOI:10.1023/A:1023328910321

Russian Journal of General Chemistry, Vol. 72, No. 11, 2002, pp. 1703 1708. Translated from Zhurnal Obshchei Khimii, Vol. 72, No. 11, 2002,
pp. 1807 1812.
Original Russian Text Copyright
2002 by Smolii, Muzychka, Chernega, Drach.
Dedicated to the centenary of Academician A.V. Kirsanov’s birthday
Two Approaches to the Transformation
of (Benzimidazol-2-ylmethyl)triphenylphosphonium Chloride
into the Derivatives of Pyrimido[1,6-a]benzimidazole
O. B. Smolii, L. V. Muzychka, A. N. Chernega, and B. S. Drach
Institute of Bioorganic and Petroleum Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received February 22, 2002
Abstract The reaction of readily accessible (benzimidazol-2-ylmethyl)triphenylphosphonium chloride
with acyl isothiocyanates in the presence of triethylamine, as well as consecutive treatment of the above
phosphonium salt first with N,N-dimethylformamide dimethyl acetal and then with phenyl or allyl isothio-
cyanate gives two types of phosphorus-containing derivatives of pyrimido[1,6-a]benzimidazole with the thione
group in position 3 or 1 of the condensed system. The structure of one of compounds of the first type, 3-thioxo-
1-p-tolyl-3,4-dihydropyrimido[1,6-a]benzimidazol-4-ylidenetriphenylphosphorane, was determined by single
crystal X-ray diffraction.
Quaternary phosphonium salts with an active
methylene group in some cases were involved in
heterocyclizations [1 4]. Readily accessible (benz-
imidazol-2-ylmethyl)triphenylphosphonium chloride
I, first described more than 25 years ago [5], can also
be classed with these reagents, but its cyclocondensa-
tion with acyl isothiothiocyanates in the presence of
triethylamine was reported only recently [6].
VIIb (Ar = 4-CH3C6H4), was unambiguously con-
firmed by single crystal X-ray diffraction (see figure;
Tables 1, 2).
The six-membered heterocycle N1C2C1C4N2C3 has
a markedly flattened half-boat conformation: the
modified Cremer Pople parametrs [7] S, , and are
0.33, 65.6 , and 25.0 , respectively; the deviations of
atoms from the least-squares plane do not exceed
0.134 . The bicyclic system N2C4N3C12 17 is planar
In this work, we studied in detail not only this
particular reaction, but also the consecutive reactions
of I with N,N-dimethylformamide dimethyl acetyl and
heterocumulenes RN=C=X, where X = O, S. As a
result we established or proposed (see scheme) the
possibility of formation from I of other functionally
substituted benzimidazoles II VI, which can be con-
verted into the corresponding pyrimido[1,6-a]benz-
imidazole derivatives VII XII. First, it should be
noted that phosphonium salt I does not react with acyl
isothiocyanates under mild conditions without adding
bases. Probably, in the presence of triethylamine,
within the 0.031
and forms with the heterocycle
N1C2C1C4N2C3 the dihedral angle of 12.3 . Because
of steric conditions, the benzene ring C5 10 is turned
relative to the six-membered heterocycle by 50.7 .
The destribution of bond lengths in the central tri-
cyclic system suggests substantial delocalization of
the electron density [8, 9]. The geometry of the tri-
phenylphosphonium moiety is usual [10].
The transformation I
...
VII is accompanied
by noticible tarring, which may be associated with the
instability of the intermediate ylides II, IV, or V.
stabilized ylide II is formed, at least in minor amounts; These ylides are probably capable of cyclization by
this species, apparently, reacts with acyl isothio-
cyanates much faster than phosphonium salt I. Since
ylide II contains pronounced C- and N-nucleophilic
centers, generation of two types of intermediates, IV
and V, may be expected. The former products are un-
doubtedly formed, at least in moderate yields, since
their dehydration products, 1-aryl-3-thioxo-3,4-di-
the intramolecular Wittig reaction (cf. [11]) to give
compounds VIII which, like many other heterylthiols
or their thione tautomers, should be very reactive and
prone to further transformations. Although we failed
to obtain direct evidence for the formation of V and
VIII, they must not be excluded from the considera-
tion, as the chain of transformations I
II
IV
hydropyrimido[1,6-a]benzimidazol-4-ylidenetriphenyl- VII is not the only possible, and the yields of the
phosphoranes VII, were isolated from the reaction
mixtures. The structure of one of them, compound
cyclization products are as low as 32 48% (Table 3).
Nevertheless, the transformation I ... VII is of
1070-3632/02/7211-1703$27.00 2002 MAIK Nauka/Interperiodica

1704
SMOLII et al.
N
N
N
N
N
+
Me2NH, H2O
N
N
PPh3Hlg
N
X
N
R
Ar
SAlk
Ar
SAlk
Xa Xf
XIa, XId XIf
XIIa, XIIb, XIIe
Ar = C6H5 (IVa, VIIa, Xa, Xd, Xf, XIa, XId, XIf), 4-CH3C6H4 (IVb, VIIb, Xb, Xc, Xe, XIe), 2,4-Cl2C6H3 (IVc,
VIIc); Alk = CH3 (Xa, XIa), n-C4H9 (Xb), CH2=CHCH (Xc), C6H5CH2 (Xd, Xe, XId, XIe), 2-ClC6H4CH2 (Xf, XIf);
2
Hlg = Cl (Xd Xf), Br (Xc), I (Xa, Xb); R = C6H5 (VIa, VIc, IXa, IXc, XIIa), 4-ClC6H4 (IXd), cyclo-C6H11 (IXe,
XIIe), CH2=CHCH2 (VIb, IXb, XIIb); X = O (VIc, IXc IXe, XIIf), S (VIa, VIb, IXa, IXb, XIIa, XIIb); Y = Cl (IXc),
ClO4 (IXa, IXb, IXd, IXe).
obvious preparative interest, since no other routes to
stabilized ylides VII have been found yet, and the
importance of these agents for prepatring pyrido[1,6-a]-
benzimidazole derivatives is beyond doubt. Thus,
similar to many other stabilized phosphonium ylides
containing the thiocarbonyl group, alkylation of com-
pounds VII proceeds almost exclusively at the sulfur
The alkylation products X are readily dephosphory-
lated under the action of aqueous dimethylamine solu-
tion; we used this reaction for preparing a series of
previously unknown 3-alkylthio-1-arylpyrimido[1,6-a]-
benzimidazoles XI. Other derivatives of pyrimido-
[1,6-a]benzimidazole were prepared by the sequence
of transformations I
III
VI
IX
XII
1
atom, which was shown by H NMR spectroscopy.
presented in the scheme. The key stages in this
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TWO APPROACHES TO THE TRANSFORMATION
1705
C34
C33
C17
C35 C26
C16
C32
C12
C27
C28
N3
C25
C15
C30
C31
C4
P1
C24
C92
C23
C14
C13
C1
C2
C18
N2
C22
C19
C10
C21
C5
C20
C3
N1
S1
C9
C8
C6
C7
C11
General view of the molecule of VIIb (hydrogen atoms are not shown).
process are condensation of phosphonium salt I with
N,N-dimethylformamide dimethyl acetal and the re-
action of the new derivative of 2-vinylbenzimidazole
III with aryl isocyanates, aryl isothiocyanates, and
their analogs. It should be noted that the cyclocon-
CH3CN was performed with a 0.14 0.31 0.61-mm
single crystal at room temperature on an Enraf Nonius
CAD-4 automatic four-circle diffractometer (CuK
radiation, scanning rate ratio 2 / = 1.2,
spherical segment 0 11, 13 13, 17
65 ,
l
max
h
k
densation III
...
IX occurs with the yields of
17). A total of 5509 reflections were collected, of
30 50% and also, probably, is not the only pathway
of the reaction III with heterocumulenes. The struc-
ture of compounds IX and XII is consistent with the
1H NMR data (Table 4) and also with the fact that the
analog of III containing ethoxycarbonyl moiety
instead of the triphenylphosphonio group reacts with
heterocumulenes similarly [12].
Table 1. Main bond lengths (d, ) and bond angles
( , deg) in the molecule of VIIb (solvate VIIb CH3CN)
Bond
d
Angle
S1 C2
1.679(3)
1.764(3)
1.797(3)
1.802(3)
1.807(3)
1.395(3)
1.293(4)
1.377(3)
1.407(3)
1.404(3)
1.314(3)
1.388(3)
1.412(4)
1.424(4)
1.403(4)
C1P1C18
C1P1C24
C18P1C24
C1P1C30
C18P1C30
C24P1C30
C2N1C3
C3N2C4
C4N2C13
C4N3C12
C2C1C4
112.8(1)
109.9(1)
113.2(1)
111.6(1)
101.2(1)
107.7(1)
120.1(2)
120.4(2)
106.2(2)
104.9(2)
117.3(2)
118.6(2)
121.9(2)
112.7(2)
116.6(2)
111.8(2)
104.3(2)
P1 C1
To conclude, the possible applications of the trans-
P1 C18
P1 C24
P1 C30
N1 C2
N1 C3
N2 C3
N2 C4
N2 C13
N3 C4
N3 C12
C1 C2
C1 C4
C12 C13
formation sequences I
VII
X
XI and I
III
IX XII are not still adequately studied, and we
hope that, in the nearest future, studies in this field
will be considerably extended, since both routes
substantially supplement a few previously developed
methods for preparing pyrimido[1,6-a]benzimidazole
derivatives [12, 13].
EXPERIMENTAL
N1C2C1
N1C3N2
N2C4N3
N2C4C1
N3C12C13
N2C13C12
1
The H NMR spectra were obtained on a Varian
VXR-300 spectrometer in (CD3)2SO or CDCl3 solu-
tions with TMS as a reference.
X-ray diffraction study of the solvate VIIb
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 11 2002

1706
SMOLII et al.
Table 2. Atomic coordinates and equivalent isotropic thermal parameters (Ueq, 2) in the structure of the solvate
VIIb CH3CN
Atom
x
y
z
Ueq
Atom
x
y
z
Ueq
S1
0.64395(9) 0.09297(7)
0.86736(6)
0.88804(5)
0.0483 C18
0.0326 C19
0.7469(3)
0.8867(3)
0.9689(4)
0.9119(5)
0.7743(5)
0.6902(4)
0.4636(3)
0.3884(3)
0.2403(4)
0.1679(3)
0.2413(3)
0.3900(3)
0.7208(3)
0.8398(3)
0.8942(4)
0.8313(4)
0.7161(4)
0.6600(4)
0.548(2)
0.1872(2)
0.1583(3)
0.1715(3)
0.2121(4)
0.2390(4)
0.2286(3)
0.1858(2)
0.2389(3)
0.2228(3)
0.1539(3)
0.1027(3)
0.1162(3)
0.3472(2)
0.3709(3)
0.4922(3)
0.5859(3)
0.5626(3)
0.4429(3)
0.4771(15)
0.4481(12)
0.4504(6)
1.0064(2)
1.0211(2)
1.1145(3)
1.1932(3)
1.1795(3)
1.0861(2)
0.0396
0.0480
0.0603
0.0700
0.0722
0.0557
P1
0.65500(7)
0.7512(2)
0.7172(2)
0.6482(2)
0.6974(3)
0.6997(3)
0.7608(3)
0.6891(3)
0.8250(3)
0.7768(4)
0.8405(4)
0.9524(4)
1.0026(3)
0.9395(3)
1.0196(5)
0.6453(3)
0.6857(3)
0.6827(3)
0.6435(3)
0.6058(3)
0.6056(3)
0.19464(6)
0.1190(2)
N1
N2
N3
C1
0.71717(17) 0.0391 C20
0.01184(19) 0.62424(15) 0.0335 C21
0.2000(2)
0.0841(2)
0.0379(2)
0.0931(2)
0.1068(2)
0.1765(2)
0.3000(3)
0.3788(3)
0.3375(3)
0.2141(3)
0.1346(3)
0.4232(4)
0.1660(2)
0.0491(2)
0.0075(2)
0.0588(3)
0.1760(3)
0.2306(3)
0.67312(16) 0.0370 C22
0.79041(19) 0.0354 C23
C2
0.7886(2)
0.0371 C24
0.86745(19) 0.0349
C3
0.64019(19) 0.0350 C25
0.70053(18) 0.0334 C26
0.56918(19) 0.0365 C27
0.8018(2)
0.7751(2)
0.8143(3)
0.8797(3)
0.9061(2)
0.0452
0.0578
0.0601
0.0552
0.0446
C4
C5
C6
0.5324(3)
0.4689(3)
0.4398(2)
0.4795(2)
0.5422(2)
0.3691(3)
0.0538 C28
0.0621 C29
0.0532 C30
0.0512 C31
0.0450 C32
0.0812 C33
C7
C8
0.89878(19) 0.0375
C9
0.8693(2)
0.8889(3)
0.9384(3)
0.9702(3)
0.9504(3)
0.220(1)
0.0484
0.0632
0.0665
0.0673
0.0560
0.0477
0.0539
0.0475
C10
C11
C12
C13
C14
C15
C16
C17
0.57452(19) 0.0351 C34
0.54096(19) 0.0342 C35
a
0.44323(19) 0.0389 N4
a
a
0.3802(2)
0.4127(2)
0.5094(2)
0.0453 C36
0.0489 C37
0.0440
0.4950(16)
0.4636(12)
0.2736(6)
0.372(1)
a
4
36
37
The N , C , and C atoms belong to the solvation molecule of acetonitrile.
which 5188 were symmetrically independent (Rint
0.023). The crystals of the solvate are triclinic, a
sion of 0.01 mol of phosphonium salt I [5] in 25 ml
of dry methanol, we added 0.002 mol of N,N-dimethyl-
formamide dimethyl acetal; the mixture was refluxed
for 4 h, the solvent was removed in a vacuum, and the
residue was purified by recrystallization.
9.709(2), b 11.628(2), c 14.864(3)
;
108.00(1) ,
104.18(1) , 92.28(1) ; V 1535.1(5), M 592.7, Z 2,
1
dcalc 1.29 g/cm3,
16.7 cm , F(000) 622.6, space
group P1 (no. 2). The structure was solved by the
direct method and refined by the least-squares method
in the full-matrix anisotropic approximation using the
CRYSTALS program package [14]. In the refinement
we used 4444 reflections with I > 3 (I) (388 refined
parameters, 11.5 reflections per parameter). Hydrogen
atoms were found geometrically and included in the
calculation with fixed positional and thermal param-
eters. The absorption within the crystal was taken into
account using the azimuthal scanning method [15]. In
the refinement we used the Chebyshev weight scheme
[16] with the parameters 1.41, 0.16, 0.30, and 0.54.
The final divergence factors were R 0.061 and RW
0.065, GOF 1.095. The coordinates of nonhydrogen
atoms are given in Table 2. The constants, yields, and
elemental analyses of the new compounds are pre-
sented in Table 3.
1-Aryl-3-thioxo-3,4-dihydropyrimido[1,6-a]-
benzimidazol-4-ylidenetriphenylphosphoranes
VIIa VIIc. A solution of 0.01 mole of appropriate
aryl isothiocyanate in 20 ml of acetonitrile was added
with vigorous stirring to a suspension of 0.01 mol of
phosphonium salt I in 40 ml of acetonitrile and 2 ml
of triethylamine. The mixture was kept for 4 h at 60
70 C, the solvent was removed in a vacuum, and the
residue was dissolved in 20 ml of ethanol. The pre-
cipitate was filtered off and purified by recrystalliza-
tion.
For the X-ray diffraction studies, compound VIIb
was recrystallized from a dilute acetonitrile solution.
The obtained crystals of the solvate VIIb CH3CN
were dried at 20 C as fast as possible, since they
readily give off acetonitrile.
[1-(Benzimidazol-2-yl)-2-dimethylaminoethen-1-
yl]triphenylphosphonium chloride III. To a suspen-
2-Phenyl-1-oxo-1,2-dihydropyrimido[1,6-a]-
benzimidazol-4-yltriphenylphosphonium chloride
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 11 2002

TWO APPROACHES TO THE TRANSFORMATION
1707
Table 3. Constants, yields, and elemental analyses of III, VII, and IX XII
mp,
(solvent for
recrystallization)
C
Found, %
Calculated, %
Comp. Yield,
Formula
no.
%
Cl (I)
7.43
N
P
S
Cl (I)
7.33
N
P
S
III
92
143 145 (ethanol
ether, 1: 1)
8.82 6.51
C29H27ClN3P
8.68 6.40
VIIa
VIIb
VIIc
IXa
48
37
32
30
258 260 (ethanol)
267 269 (ethanol)
263 265 (ethanol)
282 283 (acetonitrile
ether, 1: 1)
7.50 5.82
7.56 5.67
6.95 5.18
6.47 5.00
5.85 C34H24N3PS
5.59 C35H26N3PS
5.27 C34H22Cl2N3PS
5.10 C34H25ClN3O4PS
7.82 5.76
7.62 5.61
6.93 5.11
6.59 4.85
5.96
5.81
5.28
5.03
11.71
5.53
11.69
5.56
IXb
IXc
IXd
IXe
Xa
Xb
Xc
Xd
Xe
45
50
56
42
92
93
89
92
86
82
45
50
61
42
60
55
50
260 261 (ethanol)
291 292 (ethanol)
283 285 (acetonitrile) 10.78
5.46
6.58
6.70 5.17
7.63 5.71
6.44 4.77
6.67 4.97
5.36 C31H25ClN3O4PS
C34H25ClN3OP
5.89
6.35
10.80
5.65
(18.67) 6.18 4.56
(17.25) 5.71 4.21
6.25 4.59
5.34
5.23
6.98 5.14
7.53 5.55
6.41 4.73
6.70 4.94
5.38
C34H24Cl2N3O5P
C34H30ClN3O5P
287 289 (acetonitrile)
257 259 (ethanol)
218 220 (ethanol)
242 244 (ethanol)
246 248 (ethanol)
157 159 (ethanol)
238 239 (ethanol)
201 203 (ethanol)
164 165 (ethanol)
158 160 (ethanol)
146 148 (ethanol)
193 194 (ethanol)
150 151 (ethanol)
168 170 (ethanol)
5.61
(18.72) 6.13 4.53
(17.29) 5.73 4.24
6.27 4.62
5.41
5.19
4.68 C35H27IN3PS
4.36 C39H35IN3PS
4.79 C38H31BrN3PS
4.72
4.36
4.77
4.83
4.73
4.59
11.00
8.72
8.40
7.98
11.51
13.29
a
6.28 4.59
6.15 4.55
5.98 4.39
14.31
11.38
10.88
4.76 C41H31ClN3PS
4.68 C42H33ClN3PS
4.61 C41H30Cl2N3PS
11.15 C17H13N3S
8.73 C23H17N3S
8.32 C24H19N3S
7.92 C23H16ClN3S
11.19 C16H11N3S
12.87 C13H11N3S
C16H17N3O
6.32 4.66
6.20 4.57
6.01 4.43
14.42
11.43
11.01
Xf
10.11
10.14
XIa
XId
XIe
XIf
XIIa
XIIb
XIIe
8.75 10.38
15.09
8.82 10.45
15.15
16.83
15.94
17.41
15.72
a
Found Br, %: 11.92. Calculated Br, %: 11.88.
Table 4. 1H NMR data for III, VII, and IX XII
Comp.
no.
, ppm [(CD3)2SO]a
3
III
VIIb
2.85 br.s (6H, 2CH3), 6.90 d (1H, CH, JHH 14.0 Hz), 7.0 7.42 m (19Harom), 13.0 s (1H, NH)
2.52 c (3H, CH3), 6.41 d (1H, C9 H, JHH 8.0 Hz), 6.82 d (1Harom, JHH 8.0 Hz), 7.00 d (1Harom, JHH 8.0 Hz),
7.11 d (1Harom
3JHH 8.0 Hz), 7.40 7.90 m (19Harom
5.20 5.40 m (4H, 2CH2), 5.93 m (1H, CH=CH2), 7.45 8.00 m (19Harom), 9.42 d (1H, C3 H, JHH 9.0 Hz)
3
3
3
,
)
3
IXb
IXe
Xd
Xe
XIe
XIIa
1.00 2.10 m (10H, C6H10), 4.55 t (1H, CH), 7.24 d (1Harom, )
3JHH 12.6 Hz), 7.40 8.40 m (19Harom
4.46 s (2H, CH2), 6.75 d (1H, C9 H, JHH 8.0 Hz), 7.20 8.10 m (28Harom
)
3
2.58 s (3H, CH3), 4.46 s (2H, CH2), 6.90 d (1H, C9 H, JHH 8.0 Hz), 7.10 8.10 m (27Harom
)
)
3
2.57 s (3H, CH3), 4.48 s (2H, CH2), 6.61 d (1H, C9 H, JHH 8.0 Hz), 7.10 7.80 m (13Harom
3
3
7.19 d (1Harom
,
3JHH 7.0 Hz), 7.50 7.60 m (7Harom), 7.86 d (1H, C4 H, JHH 8.0 Hz), 7.92 d (1Harom
,
3JHH 7.0 Hz), 9.41 d (1H, C3 H, JHH 8.0 Hz)
3
3
XIIb
XIIe
5.15 5.45 m (4H, 2CH2), 6.05 m (1H, CH=CH2), 6.95 7.60 m (4Harom), 7.86 d (1H, C4 H, JHH 8.0 Hz), 9.54 d
(1H, C3 H, JHH 8.0 Hz)
3
3
1.00 1.90 m (10H, C6H10), 4.61 br.s (1H, CH), 6.72 d (1Harom, JHH 7.0 Hz), 7.35 7.83 m (4Harom), 8.37 d
(1Harom,
3JHH 7.0 Hz)
a
For XIIb, CDCl was used as solvent.
3
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SMOLII et al.
IXc. To a suspension of 0.01 mol of phosphonium
salt III in 20 ml of acetonitrile, we added 0.02 mol of
phenyl isocyanate; the mixture was kept for 2 h at 60
70 C, and the precipitate was filtered off and re-
crystallized from ethanol.
2. Smolii, O.B., Brovarets, V.S., Pirozhenko, V.V., and
Drach, B.S., Zh. Obshch. Khim., 1988, vol. 58, no. 12,
p. 2635.
3. Brovarets, V.S., Smolii, O.B., Vdovenko, S.I., and
Drach, B.S., Zh. Obshch. Khim., 1990, vol. 60, no. 3,
p. 566.
2-Allyl(cyclohexyl, phenyl, or p-chlorophenyl)-1-
oxo(thioxo)-1,2-dihydropyrimido[1,6-a]benzim-
idazol-4-yltriphenylphosphonium perchlorates IXa,
IXb, IXd, and IXe. To a suspension of 0.01 mol of
phenylphosphonium salt III in 20 ml of acetonitrile,
we added 0.02 mol of appropriate heterocumulene;
the mixture was kept for 2 h at 60 70 C, and the
solvent was removed in a vacuum. The residue was
dissolved in 20 ml of ethanol, and 10 ml of saturated
aqueous solution of sodium perchlorate was added.
The precipitate that formed was filtered off, washed
with water, and purified by recrystallization.
4. Smolii, O.B., Panchishin, S.Ya., Romanenko, E.A.,
and Drach, B.S., Zh. Obshch. Khim., 1999, vol. 69,
no. 10, p. 1652.
5. Popov, I.I., Simonov, A.M., and Zubenko, A.A., Khim.
Heterotsikl. Soedin., 1976, no. 8, p. 1145.
6. Smolii, O.B., Shakhnin, D.B., and Drach, B.S., Zh.
Obshch. Khim., 1995, vol. 65, no. 7, p. 1225.
7. Zefirov, N.S. and Palyulin, V.A., Dokl. Akad. Nauk
SSSR, 1980, vol. 252, no. 1, p. 111.
8. Allen, F.H., Kennard, O., Watson, D.G., Brammer, L.,
Orpen, A.G., and Tailor, R., J. Chem. Soc., Perkin
Trans. 2, 1987, no. 12, p. S1.
3-Alkylthio-1-arylpyrimido[1,6-a]benzimidazol-
4-yltriphenylphosphonium halides Xa Xf. To a
solution of 0.01 mol of VIIa VIIc in 40 ml of me-
thylene chloride, we added 0.011 mol of alkyl halide;
the mixture was kept for 12 h at 20 25 C. The solvent
was removed in a vacuum, and the residue was
purified by crystallization.
9. Burke-Laing, M. and Laing, M., Acta Crystallogr.,
Sect. B, 1976, vol. 32, no. 12, p. 3216.
10. Naumov, V.A. and Vilkov, L.V., Molekulyarnye
struktury fosfororganicheskikh soedinenii (Molecular
Structures of Organophosphorus Compounds),
Moscow: Nauka, 1986, p. 320.
3-Alkylthio-1-arylpyrimido[1,6-a]benzimid-
azoles XIa and XId XIf. To a solution of 0.01 mol
of Xa or Xd Xf in 50 ml of acetonitrile, we added a
solution of 0.04 mol of dimethylamine in 2 ml of
water; the mixture was kept for 12 h at 20 25 C. The
precipitate that formed was filtered off and purified by
recrystallization.
11. Eitel, M. and Pindur, U., Synthesis, 1989, no. 5,
p. 364.
12. Meziane, M.A.A., Rahmouni, M., Bazureau, J.P., and
Hamelin, J., Synthesis, 1998, no. 7, p. 967.
13. Preston, P.N., Benzimidazoles and Congeneric Tri-
cyclic Compounds, The Chemistry of Heterocyclic
Compounds, Weissberger, A., Ed., New York: Inter-
science, 1980, vol. 40, part 2, pp. 341 389.
2-Allyl(cyclohexyl, phenyl)-1-oxo(thioxo)-1,2-
dihydropyrimido[1,6-a]benzimidazoles XIIa, XIIb,
and XIIe. To a solution of 0.01 mol of XIa, XIb, or
XIe in 50 ml of acetonitrile, we added 0.01 mol of
sodium hydroxide; the mixture was kept for 12 h at
20 25 C. The solvent was removed in a vacuum, and
the residue was purified by crystallization.
14. Watkin, D.J., Prout, C.K., Carruthers, J.R., and
Betteridge, P.W., CRYSTALS, issue 10, Chemical
Crystallography Laboratory, Univ. of Oxford, 1996.
15. North, A.C.T., Phillips, D.C., Scott, F., and
Mathews, F.S., Acta Crystallogr., Sect. A, 1968,
vol. 24, no. 2, p. 351.
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1. Smolii, O.B., Brovarets, V.S., and Drach, B.S., Zh.
Obshch. Khim., 1988, vol. 58, no. 7, p. 1670.
16. Carruthers, J.R. and Watkin, D.J., Acta Crystallogr.,
Sect. A, 1979, vol. 35, no. 3, p. 698.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 11 2002