4-Hydroxy-2-quinolones 123. Amidation of 2-bromomethyl-5-oxo-1,2-dihydro- 5H-oxazolo[3,2-a]-quinoline-4-carboxylic acid

Article abstract of DOI:10.1007/s10593-007-0138-2

The reaction of 2-bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]quinoline- 4-carboxylic acid with thionyl chloride is accompanied by a transformation of the oxazoloquinolone ring to give 4-chloro-1-(2,3-dichloropropyl)-2-oxo-1,2- dihydroquinoline-3-carboxylic acid chloride.

Full text of DOI:10.1007/s10593-007-0138-2

Chemistry of Heterocyclic Compounds, Vol. 43, No. 7, 2007
4-HYDROXY-2-QUINOLONES
123*. AMIDATION OF 2-BROMOMETHYL-
5-OXO-1,2-DIHYDRO-5H-OXAZOLO[3,2-a]-
QUINOLINE-4-CARBOXYLIC ACID
I. V. Ukrainets1, N. L. Bereznyakova1, A. V. Turov2, and S. V. Shishkina3
The reaction of 2-bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]quinoline-4-carboxylic acid with
thionyl chloride is accompanied by a transformation of the oxazoloquinolone ring to give 4-chloro-
1-(2,3-dichloropropyl)-2-oxo-1,2-dihydroquinoline-3-carboxylic acid chloride.
Keywords: oxazolo[3,2-a]quinoline, 4-chloro-2-quinolinone, amidation, ring closing, X-ray analysis.
Using various methods, carboxylic acids can be converted to N-substituted amides which are potentially
biologically active substances. None the less, only a few of these are widely used in preparative organic
chemistry. The best known are the reaction of the acids to an acid chloride or to the imidazolide by treatment
with thionyl chloride or N,N'-carbonyldiimidazole (CDI) respectively. We have studied the potential use of these
methods for the amidation of the recently reported 2-bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]-
quinoline-4-carboxylic acid (1).
It was found that the reaction of acid 1 with both thionyl chloride and CDI occurred without any obvious
complication. Hence subsequent work up of the intermediate quinolones 2 and 3 with p-anisidine should
theoretically have given the same 4-methoxyanilide of 2-bromomethyl-5-oxo-1,2-dihydro-5H-
oxazolo[3,2-a]quinoline-4-carboxylic acid (5). However, the actual properties of the anilides 4 and 5 obtained
proved to be different. It was initially proposed that, in the case of the use of CDI there might occur a
nucleophilic substitution of the bromine in acid 1 for an imidazole residue but this was not correct since the
corresponding imidazole signals were absent in the 1H and 13C NMR spectra. Further, a comparative analysis of
1
the H NMR spectra of the material obtained and of the synthetic precursor (acid 1) showed that the thionyl
chloride led to a marked change in the oxazoloquinolone skeleton whereas in the case of CDI the nature of the
spectrum was little changed.
A similar conclusion was reached when looking at the 13C NMR spectra of anilides 4 and 5 and after
hydrolysis of the proposed acid chloride to form acid 6 which has properties and spectroscopic characteristics
different to the starting acid.
_______
* For Communication 122 see [1].
__________________________________________________________________________________________
1National University of Pharmacy, Kharkiv 61002, Ukraine; e-mail: uiv@kharkov.ua. 2Taras
3
Shevchenko National University, Kiev 01033, Ukraine; e-mail: nmrlab@univ.kiev.ua. STC Institute for Single
Crystals, National Academy of Sciences, Kharkiv 61001 Ukraine; e-mail: sveta@xray.isc.kharkov.com.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1034-1042, July, 2007. Original article
submitted March 23, 2006.
0009-3122/07/4307-0871©2007 Springer Science+Business Media, Inc.
871

OMe
Cl
N
O
Cl
N
O
N
H
Cl
p-anisidine
O
O
Cl
Cl
Cl
Cl
H2O
2
4
SOCl2
O
Cl
O
O
OH
OH
N
O
N
Cl
O
1
Cl
Br
6
CDI
O
OMe
O
N
O
O
O
p-anisidine
N
N
H
N
N
O
Br
Br
5
3
However, the question of what had occurred to acid 1 under these conditions remained open.
The answer to this problem was resolved after treatment of ethyl 2-bromomethyl-5-oxo-1,2-dihydro-
5H-oxazolo[3,2-a]quinoline-4-carboxylate (7) with thionyl chloride.
It proved possible to grow a single crystal of the compound obtained suitable for X-ray analysis and this
allowed us to identify it unambiguously as ethyl 4-chloro-1-(2,3-dichloropropyl)-2-oxo-1,2-dihydroquinoline-
3-carboxylate (8). The initial stage of this unusual reaction is evidently addition of HCl, traces of which are
always present in thionyl chloride. The 4-hydroxy derivative 9 then undoubtedly undergoes three reactions
which are: nucleophilic aromatic substitution of the OH group, fission of an ether bond in the oxazolidine ring,
and finally exchange of the bromine atom for chlorine. At this time it was not possible to prove unambiguously
whether these processes occur simultaneously or in some particular kind of sequence.
O
O
Cl
O
OH
O
SOCl2
OEt
OEt
OEt
Cl
HCl
+
N
N
O
N
O
O
Cl
9
7
8
Br
Br
Cl
872

From the X-ray data it was found that the bicyclic fragment and the Cl(1), C(10), O(1), and C(13) atoms of
the ethyl ester 8 lie within a single plane to an accuracy of 0.01 Å (Figure 1, Tables 1, 2). A shortened
intramolecular contact for H(5)···Cl(1) of 2.66 Å is found (sum of van der Waal radii 3.06 Å [2]). The ester
substituent is twisted relative to the plane of the bicycle (torsional angle C(7)–C(8)–C(10)–O(2) 89.3(5)º). The ethyl
group occurs in an ap conformation relative to the C(8)–C(10) bond and the C(11)–C(12) bond is virtually
perpendicular to the C(10)–O(3) bond (torsional angles C(11)–O(3)–C(10)–C(8) -179.5(3)º, C(10)–O(3)–C(11)–C(12)
-85.3(4)º). This positioning of the ethyl group leads to a shortened intramolecular contact H(11a)···O(2) 2.40 Å
(2.46 Å).
Fig. 1. Structure of the trichloro-substituted ester 8 molecule with atomic numbering.
There is a repulsion between the substituent on atom N(1), the neighboring carbonyl group, and the
hydrogen in the peri position of the benzene ring [intramolecular shortened contacts H(2)···C(13) 2.60 (2.87),
H(2)···H(13a) 1.95 (2.34), H(13a)···C(2) 2.51 (2.87), H(13b)···O(2) 2.38 (2.46), and H(14)···C(9) 2.84 Å (2.87 Å)] which
results in the dichloropropyl substituent being almost perpendicular to the plane of the bicyclic fragment
(torsional angle C(9)–N(1)–C(13)–C(14) 78.1(3)º) and found in an ap conformation (torsional angle N(1)–C(13)–C(14–C(15)
-175.8(3)º). The chlorine atoms in it occur in a -sc-position relative to one another (torsional angle Cl(2)–C(14)
–
C
(15)–Cl(3) -65.1(3)º despite the shortened intramolecular contact Cl(2)···C(1) to 3.53 Å (3.61 Å).
TABLE 1. Bond Lengths (l) in the Trichloro-substituted Ester 8
Bond
l, Å
Bond
l, Å
Cl(1)–C(7)
N(1)–C(9)
O(1)–C(9)
C(1)–C(6)
O(2)–C(10)
Cl(3)–C(15)
O(3)–C(11)
C(4)–C(5)
C(6)–C(7)
C(8)–C(9)
C(11)–C(12)
C(14)–C(15)
1.760(3)
1.386(4)
1.224(4)
1.416(5)
1.186(4)
1.844(4)
1.462(4)
1.382(8)
1.434(5)
1.460(4)
1.486(6)
1.499(5)
N(1)–C(1)
N(1)–C(13)
C(1)–C(2)
Cl(2)–C(14)
C(2)–C(3)
O(3)–C(10)
C(3)–C(4)
C(5)–C(6)
C(7)–C(8)
C(8)–C(10)
C(13)–C(14)
1.386(4)
1.467(4)
1.409(5)
1.827(3)
1.352(6)
1.321(4)
1.393(8)
1.388(5)
1.321(5)
1.499(4)
1.520(5)
873

TABLE 2. Valence Angles (ω) in the Trichloro-substituted Ester 8
Angle
(1)–N(1)–C(9)
ω, deg
Angle
C(1)–N(1)–C(13)
ω, deg
C
123.0(2)
113.7(2)
120.4(3)
120.7(4)
121.7(4)
121.4(5)
124.5(4)
123.6(3)
117.8(2)
125.1(3)
121.3(3)
116.3(2)
123.8(3)
111.2(3)
108.8(3)
111.7(2)
123.2(2)
121.4(3)
118.2(3)
117.0(3)
118.5(4)
119.5(4)
116.1(3)
118.6(3)
120.6(3)
114.3(3)
122.3(3)
124.6(3)
111.6(2)
113.3(2)
110.9(2)
111.9(3)
C(9)–N(1)–C(13)
N(1)–C(1)–C(6)
C(3)–C(2)–C(1)
C(2)–C(3)–C(4)
C(4)–C(5)–C(6)
C(5)–C(6)–C(7)
C(8)–C(7)–C(6)
C(6)–C(7)–Cl(1)
C(7)–C(8)–C(10)
O(1)–C(9)–N(1)
N(1)–C(9)–C(8)
O(2)–C(10)–C(8)
O(3)–C(11)–C(12)
C(15)–C(14)–C(13)
C(13)–C(14)–Cl(2)
N(1)–C(1)–C(2)
C(2)–C(1)–C(6)
C(10)–O(3)–C(11)
C(5)–C(4)–C(3)
C(5)–C(6)–C(1)
C(1)–C(6)–C(7)
C(8)–C(7)–Cl(1)
C(7)–C(8)–C(9)
C(9)–C(8)–C(10)
O(1)–C(9)–C(8)
O(2)–C(10)–O(3)
O(3)–C(10)–C(8)
N(1)–C(13)–C(14)
C(15)–C(14)–Cl(2)
C(14)–C(15)–Cl(3)
The ester molecule 8 forms stacks in the crystal along the crystallographic (1 0 0) direction and these are
mutually linked by weak intermolecular hydrogen bonds C(13)–H(13a)···O(2') (1+x, y, z) H···O 2.39 Å, C–H···O 133º,
C(15)–H(15b)···O(1') (1-x, 2-y, 1-z) H···O 2.43 Å, C–H···O 162º. Shortened intermolecular contacts occur in the
crystal as H(4)···Cl(3') (x, y, z-1) 2.98 (3.06), H(11b)···Cl(2') (x-1, y+1, z) 2.06 (3.06), Cl(1)···Cl(1') (-x, 2-y, -z) 3.45 (3.80),
Cl(1)···Cl(3') (1-x, 1-y, 1-z) 3.58 (3.80), Cl(2)···C(9') (1-x, 1-y, 1-z) 3.58 (3.61), Cl(3)···C(7') (1-x, 1-y, 1-z) 3.57 Å (3.61 Å).
13
Based on the X-ray data obtained all of the NMR data fell into place. Hence the C NMR spectrum of
the anilide 4 fully agrees with its structure as the acyclic trichloro derivative. Pointing to this is the anomalously
high field chemical shift for the C(4) atom in the quinoline fragment at 140.7 ppm. Such a position would in no
way be possible for a corresponding carbonyl carbon atom. In addition, the β-carbon atom signal in the
N(1)-substituent also agrees fully with a -CHCl- group. For this compound the following carbon and proton
chemical shifts were obtained.
H
H 3.75
H
55.9
O
8.08
156.3
H
Cl
O
132.5
114.7
140.7
118.4
126.9
161.2
H
124.3
7.46
H
N
6.93
121.4
H
129.6
O
10.42
H
133.4
H
139.1
N
7.57
158.9
116.4
7.82
7.80
H
4.82
Cl
47.2
H
H
58.9
36.8
4.71
H
4.85
H
Cl
H
4.00
874

TABLE 3. Full Correlation List Found for the Anilide 4
δ, ppm
НМQC
HMBC
10.42
8.08
7.82
7.80
7.57
7.46
6.93
4.85
4.82
4.71
4.00
3.75
—
161.2; 132.5; 121.4
140.7; 139.1; 133.4
126.9
116.4
133.4
121.4
124.3
114.7
47.2
139.1; 126.9; 124.3; 118.4
156.30; 132.5; 121.4
118.4; 116.4
156.3; 132.5
58.9; 36.8; 158.9; 139.1
47.2
58.9
47.2
36.8
58.9; 36.8; 158.9; 139.1
58.98; 47.2
55.9
156.3
Assignment of the protonated carbon atoms was made on the basis of the HMQC spectra and that of the
quaternary carbon atoms through correlation with HMBC spectra. Hence the assignment of the C(8a) carbon atom
follows from its correlation with the H-5,7 proton and the N–CH2 methylene group protons. Assignment of the
chemical shift of the C(4a) atom was made from its correlation with the H-6 and H-8 protons. Atom C(4), which is
bonded to the chlorine, has a strong correlation through three bonds with the H-5 proton and it can be specified
with certainty. The carbonyl C(2) atom is assigned on the basis of its correlation with the N–CH2 methylene
group protons.
The signal for the amide carbonyl at C(3) was assigned from its correlation with the amide NH proton.
The single carbon atom for which no proton correlation was found is the C(3) atom so is attributed by exclusion.
The chemical shift of this atom is typical of conjugated systems. The most important HMBC correlations serving
as the basis of the assignment are shown in the scheme and the full list is presented in Table 3.
Although it contains the same number of protons, the proton spectrum of the alternative anilide 5 differs
markedly in chemical shifts. The signal assignments were made from their multiplicities and by the presence of
cross peaks in the COSY spectrum. In the carbon spectrum of this compound the signal for the quinoline ring
C(5) atom has a chemical shift of 177.7 ppm which is typical of a conjugated carbonyl group.
H
H
H
3.72
55.9
O
8.25
H
155.7
O
O
133.2
7.48
127.0
114.7
H
161.6
177.7
H
H
125.1
N
H
12.33
96.3
121.5
124.2
135.1
N
6.88
134.0
116.7
163.0
O
H
7.58
7.81
49.3
H
7.56
80.9
H
4.02
H
H
4.68
H
H
5.68
4.31
35.1
Br
875

TABLE 4. Full Correlation List Found for the Oxazoloquinolone 5
∆, ppm
НМQC
HMBC
12.33
8.25
7.81
7.58
7.56
7.48
6.88
5.68
4.68
4.31
4.02
3.72
—
96.3; 121.5; 133.2
177.7; 135.1; 134.0
135.1; 127.0
127.0
134.0
121.5
116.7
125.1
114.7
80.9
155.7; 133.2; 121.5
125.1; 124.2
124.2; 116.7
155.7; 133.2; 114.7
163.0
49.3
163.0; 80.9; 35.1
163.0; 80.9; 35.1
80.9; 49.3
49.3
35.1
55.9
155.7
The C(2) atom of the oxazolidine ring has a chemical shift of 80.9 ppm which confirms its bonding to an
oxygen atom. Assignment of the remaining signals follows from the observed HMBC and HMQC correlations.
Hence the assignment of the 124.2 ppm signal to the bridging C(5a) atom follows from the presence of its
correlation with atoms H-7 and H-9 and of the signal at 135.1 ppm to the C(9a) atom from its correlation through
three bonds to the H-6 and H-8 atoms. The signal for the quinoline C(3a) atom was interpreted through its
correlation with the methylene protons on the heterocyclic nitrogen atom and for the C(4) atom from its
correlation with the amide NH group proton. The assignment of the signals in the oxazolidine ring also follows
securely from the correlations found. Both the methylene protons and the CH proton have a correlation through
three bonds with the quinoline C(3a) atom and this possibility is exclusive to a cyclic structure for the compound.
It should be noted, however, that the correlation of the proton at 5.68 ppm (atom H-2 of the oxazolidine ring)
and the quinoline ring C(3a) is extremely weak. It can only be observed by increasing the mixing time in the pulse
sequence to 100 ms. When doing so the correlations with larger spin spin couplings become invisible. The
assignments of the remaining signals are given in the scheme and in Table 4. Hence all of the data given agrees
with the proposed anilide structures 4 and 5.
EXPERIMENTAL
1
1H and 13C NMR spectra for the 4-methoxyanilides 4 and 5, 2D H NMR COSY experiments,
homonuclear Overhauser effect NOESY-1D, and HMQC and HMBC heteronuclear correlation spectra were
recorded on a Varian Mercury-400 (400 MHz) spectrometer (400 and 100 MHz respectively). All of the 2D
experiments were carried out with a gradient selection of useful signals. The mixing times in the pulse sequences
were 1JCH = 140 and 2,3JCH = 8 Hz respectively. The number of increments in the COSY and HMQC spectra was
1
128 and in the HMBC spectra 400. The mixing time in the NOESY-1D experiment was 500 ms. H NMR
spectra for the remaining compound were taken on a Varian Mercury VX-200 (200 MHz) instrument. In all
cases the solvent was DMSO-d6 and the internal standard TMS.
2-Bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]quinoline-4-carboxylic acid (1) and its ethyl ester
7 were prepared as in the method in [3]. The N,N'-carbonyldiimidazole and anhydrous DMF for peptide
synthesis came from the Fluka company.
4-Chloro-1-(2,3-dichloropropyl)-2-oxo-1,2-dihydroquinoline-3-carboxylic Acid 4-Methoxyanilide
(4). A mixture of 2-bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]quinoline-4-carboxylic acid (1) (3.24 g,
0.01 mol) and SOCl2 (30 ml) was refluxed for 10 h. Excess SOCl2 was distilled off in vacuo. The acid chloride 2
876

formed was dissolved in dry acetone (15 ml) and the solution obtained was added to a mixture of p-anisidine
(1.23 g, 0.01 mol) and triethylamine (1.4 ml, 0.01 mol) in dry acetone (20 ml) with cooling and vigorous stirring.
After 5 h the reaction mixture was diluted with cold water. The precipitated anilide 4 was filtered off, washed
1
with water, and dried. Yield 3.78 g (86%); mp 188-190ºC (acetone). H NMR spectrum, δ, ppm (J, Hz): 10.42
(1H, s, NH); 8.08 (1H, d, J = 8.1, H-5); 7.82 (2H, m, H-7,8); 7.57 (2H, d, J = 8.7, H-2',6'); 7.46 (1H, t, J = 7.3,
H-6); 6.93 (2H, d, J = 8.7, H-3',5'); 4.85 (1H, m, NCH); 4.82 (1H, m, NCH2CHCl); 4.71 (1H, m, NCH); 4.00
13
(2H, m, CH2Cl); 3.75 (3H, s, OCH3). C NMR spectrum, δ, ppm: 161.2 (C(3)=O); 158.9 (C(2)=O); 156.3 (C(4'));
140.7 (C(4)); 139.1 (C(8a)); 133.4 (C(7)); 132.5 (C(1')); 129.6 (C(3)); 126.9 (C(5)); 124.3 (C(6)); 121.4 (C(2',6')); 118.4
(C(4a)); 116.4 (C(8)); 114.7 (C(3',5')); 58. (NCH2CHCl); 55.9 (OCH3); 47.2 (NCH2)); 36.8 (CH2Cl). Found, %: C
54.55; H 3.81; N 6.47. C20H17Cl3N2O3. Calculated, %: C 54.63; H 3.90; N 6.37.
2-Bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]quinoline-4-carboxylic Acid 4-Methoxy-
anilide (5). N,N'-Carbonyldiimidazole (1.62 g, 0.01 mol) was added to a solution of compound 1 (3.24 g,
0.01 mol) in anhydrous DMF (20 ml). The reaction mixture was stirred at 55-60ºC until CO2 evolution had
finished (about 2 h) with protection from atmospheric moisture. p-Anisidine (1.23 g, 0.01 mol) was added to the
obtained imidazolide 3 and heating was continued for a further 3 h. The cooled reaction mixture was diluted with
water. The precipitated anilide 5 was filtered off, washed with water, and dried. Yield 3.90 g (91%);
mp 227-229ºC (ethanol). 1H NMR spectrum, δ, ppm (J, Hz): 12.33 (1H, s, NH); 8.25 (1H, d, J = 7.8, H-6); 7.81
(1H, t, J = 7.3, H-8); 7.58 (2H, d, J = 8.8, H-2',6'); 7.56 (1H, d, J = 8.5, H-9); 7.48 (1H, t, J = 7.3, H-7); 6.88
(2H, d, J = 8.8, H-3',5'); 5.68 (1H, m, NCH2CHO); 4.68 (1H, t, J = 9.8, NCH): 4.31 (1H, dd, J = 6.6 and 9.7,
NCH); 4.02 (2H, m, CH2Br); 3.72 (3H, s, OCH3). 13C NMR spectrum, δ, ppm: 177.7 (C(5)=O); 163.0 (C(3a));
161.6 (C(4)=O); 155.7 (C(4)’); 135.1 (C(9a)); 134.0 (C(8)); 133.2 (C(1')); 127.0 (C(6)); 125.1 (C(7)); 124.2 (C(5a));
121.5 (C(2',6')); 116.7 (C(9)); 114.7 (C(3',5')); 96.3 (C(4)); 80.9 (NCH2CHO); 55.9 (OCH3); 49.3 (NCH2); 35.1
(CH2Br). Found, %: C 55.84; H 4.10; N 6.46. C20H17BrN2O4. Calculated, %: C 55.96; H 3.99; N 6.53.
4-Chloro-1-(2,3-dichloropropyl)-2-oxo-1,2-dihydroquinoline-3-carboxylic Acid (6). The obtained
acid chloride 2 (see the above synthesis of anilide 4) was treated with water (20 ml), thoroughly stirred, and left
for 2-3 h at room temperature. The acid 6 formed was filtered off, washed with water, and dried. Yield 3.17 g
1
(95%); mp 167-169ºC (ethanol). H NMR spectrum, δ, ppm (J, Hz): 12.11 (1H, br. s, COOH); 8.03 (1H, d,
J = 8.0, H-5); 7.81-7.74 (2H, m, H-7,8); 7.44 (1H, t, J = 7.7, H-6); 4.90-4.53 (3H, m, NCH2CH); 4.04 (2H, m,
CH2Cl). Found, %: C 46.76; H 3.13; N 4.10. C13H10Cl3NO3. Calculated, %: C 46.67; H 3.01; N 4.19.
Ethyl 4-Chloro-1-(2,3-dichloropropyl)-2-oxo-1,2-dihydroquinoline-3-carboxylate (8). A solution of
ethyl 2-bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]quinoline-4-carboxylate 7 (3.52 g, 0.01 mol) and
SOCl2 (30 ml) was refluxed for 10 h. Excess SOCl2 was distilled off in vacuo. The residue was treated with cold
water. The precipitated ester 8 was filtered off, washed with water, and dried. Yield 3.26 g (90%); mp 84-86ºC
1
(ether). H NMR spectrum, δ, ppm (J. Hz): 8.03 (1H, d, J = 8.1, H-5); 7.83-7.76 (2H, m, H-7,8); 7.44 (1H, t,
J = 7.6, H-6); 4.89-4.52 (3H, m, NCH2CH); 4.34 (2H, q, J = 7.2, COOCH2); 4.03 (2H, m, CH2Cl); 1.29 (3H, t,
J = 7.0, CH3). Found, %: C 49.57; H 3.75; N 3.77. C15H14Cl3NO3. Calculated, %: C 49.68; H 3.89; N 3.86.
X-ray Structural Study. Crystals of the trichloro-substituted ester 8 (from diethyl ether) are triclinic, at
20ºC: a = 8.503(1), b = 9.109(1), c = 11.987(2) Å, α = 68.89(1), β = 79.20(1), γ = 73.48(1)º, V = 826.0(2) Å3,
M = 362.62, Z = 2, space group P , d = 1.458 g/cm3, µ(MoKα) = 0.565 mm-1, F(000) = 372. The unit cell
1
r
calc
parameters and intensities of 7949 reflections (2277 independent, Rint = 0.017) were measured on an Xcalibur-3
diffractometer (MoKα, CCD detector, graphite monochromator, ω-scanning, 2θmax = 60º).
The structure was solved by a direct method using the SHELXTL program package [4]. The positions of
the hydrogen atoms were revealed from electron density difference synthesis and refined using the riding model
with Uiso = nUeq for a non-hydrogen atom bonded to the given hydrogen (n = 1.5 for a methyl group and n = 1.2 for
remaining hydrogen atoms). The structure was refined using F2 full matrix least squares analysis in the
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anisotropic approximation for non-hydrogen atoms to wR2 = 0.205 for 4648 reflections (R1 = 0.075 for 2606
reflections with F>4σ(F), S = 0.959). The complete crystallographic information has been placed in the
Cambridge structural data bank (reference CCDC 604004). The interatomic distances and valence angles are
given in Tables 1 and 2.
REFERENCES
1.
I. V. Ukrainets, E. V. Mospanova, and L. V. Sidorenko, Khim. Geterotsikl. Soedin., 1023 (2007). [Chem.
Heterocycl. Comp., 43, 863 (2007)].
2.
3.
Yu. V. Zefirov, Kristallografiya, 42, 936 (1997).
I. V.Ukrainets, L. V. Sidorenko, O. V. Gorokhova, S. V. Shishkina, and A. V. Turov, Khim. Geterotsikl.
Soedin., 736 (2007). [Chem. Heterocycl. Comp., 43, 617 (2007)].
4.
G. M. Sheldrick, SHELXTL PLUS PC Version. A System of Computer Programs for the Determination
of Crystal Structure from X-ray Diffraction Data, Revision 5.1 (1998).
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