Cyclic and acyclic products from the reactions between methyl 3-oxo-butanoate and aryl-hydrazines

Article abstract of DOI:10.1107/S0108270107029447

The mol-ecules of methyl 3-(2-nitro-phenyl-hydrazono)-butan-oate, C11H13N3O4, (I), and methyl 3-(2,4-dinitro-phenyl-hydrazono)butanoate, C11H12N4O6, (II), both prepared from methyl 3-oxobutanoate and the corresponding nitro-phenyl-hydrazine, exhibit polarized mol-ecular electronic structures; in each of (I) and (II), the mol-ecules are linked into chains by a single C - H...O hydrogen bond. The mol-ecules of 5-hydroxy-3-methyl-1-phenyl-1H- pyrazole, C10H10N2O, (III), prepared by the reaction of methyl 3-oxobutanoate and phenyl-hydrazine, are linked into chains by a single O - H...N hydrogen bond. The reaction between methyl 3-oxobutanoate and 3-nitro-phenyl-hydrazine yields 5-hydr-oxy-3-methyl-1-(3-nitro-phen-yl)-1H-pyrazole, (IV), which when crystallized from acetone yields 4-isopropyl-idene-3-methyl-1-(3-nitro-phen-yl)- 1H-pyrazol-5(4H)-one, C13H13N3O3, (V). International Union of Crystallography 2007.

Full text of DOI:10.1107/S0108270107029447

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Compounds (I)±(III) (Figs. 1±3) were readily obtained from
the reactions between methyl 3-oxobutanoate and the
appropriate arylhydrazines, viz. 2-nitrophenylhydrazine for
(I), 2,4-dinitrophenylhydrazine for (II) and phenylhydrazine
for (III). The analogous reaction using 3-nitrophenylhydrazine
gave the product (IV), but the crystals initially obtained from
methanol solution were of very poor quality and were
twinned. The diffraction data obtained from these crystals
were correspondingly poor, and we have been unable to
reduce R signi®cantly below 0.11; thus, we do not report the
structure of (IV) in detail here. Nonetheless, the atom
connectivity revealed by these very poor data unambiguously
corresponds to that of compound (IV), directly analogous to
compound (III). Attempted recrystallization of compound
(IV) from acetone solution yielded instead the condensation
product (V) (Fig. 4), evidently a product of the reaction
between (IV) itself and the acetone solvent.
ISSN 0108-2701
Cyclic and acyclic products from the
reactions between methyl 3-oxo-
butanoate and arylhydrazines
James L. Wardell,a Janet M. S. Skakle,b John N. Lowb and
Christopher Glidewellc*
a
Â
Â
Ã
Instituto de Quõmica, Departamento de Quõmica Inorganica, Universidade Federal
do Rio de Janeiro, 21945-970 Rio de Janeiro, RJ, Brazil, bDepartment of Chemistry,
University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, and
cSchool of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland
Correspondence e-mail: cg@st-andrews.ac.uk
Received 14 June 2007
Accepted 15 June 2007
Online 14 July 2007
The molecules of methyl 3-(2-nitrophenylhydrazono)butan-
oate, C11H13N3O4, (I), and methyl 3-(2,4-dinitrophenyl-
hydrazono)butanoate, C11H12N4O6, (II), both prepared from
methyl 3-oxobutanoate and the corresponding nitrophenyl-
hydrazine, exhibit polarized molecular electronic structures; in
each of (I) and (II), the molecules are linked into chains by a
single CÐHÁ Á ÁO hydrogen bond. The molecules of 5-hydroxy-
3-methyl-1-phenyl-1H-pyrazole, C10H10N2O, (III), prepared
by the reaction of methyl 3-oxobutanoate and phenyl-
hydrazine, are linked into chains by a single OÐHÁ Á ÁN
hydrogen bond. The reaction between methyl 3-oxobutanoate
and 3-nitrophenylhydrazine yields 5-hydroxy-3-methyl-1-(3-
nitrophenyl)-1H-pyrazole, (IV), which when crystallized from
acetone yields 4-isopropylidene-3-methyl-1-(3-nitrophenyl)-
1H-pyrazol-5(4H)-one, C13H13N3O3, (V).
Comment
We have for a number of years been interested in the struc-
tures of hydrazones (for examples, see Glidewell et al., 2003,
2004, 2006; Peralta et al., 2007; Wardell et al., 2005). As part of
this wider study, we have now investigated the reactions of
methyl 3-oxobutanoate (methyl acetoacetate) with a range of
simple arylhydrazines. The reaction products include the
acyclic 3-arylhydrazinobutanoate esters (I) and (II), the
cyclized 1-aryl-5-hydroxypyrazoles (III) and (IV), and the
condensation products such as (V), initially obtained during
attempts to crystallize the pyrazole derivatives from ketonic
solvents. We report here the structures of compounds (I)±(III)
and (V), and we integrate the various structural types into a
single mechanistic scheme. The structure of (III) reported
here represents a second polymorph of this compound; a
monoclinic polymorph crystallizes with Z0 = 2 in the space
group P21/c (Bechtel et al., 1973a; Chmutova et al., 2001).
The bond lengths in the aryl rings of (I) and (II) show
signi®cant variation (Table 1). In particular, the C3ÐC4 and
C5ÐC6 bonds are substantially shorter than the other ring
bonds; in addition, the C2ÐN12 and C4ÐN14 bonds are long
for their type, while the nitro NÐO bonds are all long (Allen
et al., 1987). The observations indicate that the polarized
o462 # 2007 International Union of Crystallography
DOI: 10.1107/S0108270107029447
Acta Cryst. (2007). C63, o462±o467

organic compounds
quinonoid forms (Ia), and (IIa) and (IIb), respectively, are
signi®cant contributors to the overall electronic structures of
(I) and (II). This behaviour is typical of that observed in
2-nitro- and 4-nitroanilines, but not in 3-nitroanilines (Cannon
et al., 2001; Garden et al., 2001, 2002; Glidewell et al., 2001;
Zakaria et al., 2001), and it indicates a reduction in the basicity
and nucleophilicity of atom N1 in such 2- and 4-substituted
species as compared with both the 3-nitro derivatives and the
un-nitrated analogues. The aryl rings in (I) and (II) are almost
coplanar with the chain-extended fragment between atoms C1
and C13 (Figs. 1 and 2), and the nitro groups are nearly
coplanar with the rings, as shown by the relevant torsion
angles (Table 1). These nearly planar conformations may be
in¯uenced by the intramolecular NÐHÁ Á ÁO interactions
(Table 2). The ester fragments between atoms C12 and C15
are also nearly planar, but in each compound there is a
substantial bend in the side chain at the C12ÐC13 bond.
Figure 1
A molecule of (I), showing the atom-labelling scheme and the intra-
molecular NÐHÁ Á ÁO hydrogen bond (dashed line). Displacement
ellipsoids are drawn at the 30% probability level.
The heterocyclic rings in (III) and (V) exhibit very different
bond lengths (Table 2), consistent with signi®cant ꢀ-delocali-
zation in (III) and complete bond ®xation in (V). The
exocyclic CÐO bond lengths, in particular, are consistent with
the location of the hydroxyl H atom in (III) as deduced from
difference maps. The inter-ring dihedral angle is 22.0 (2)ꢀ in
(III) and 6.2 (2)ꢀ in (V), where the nitro group makes a
dihedral angle of only 4.9 (2)ꢀ with the aryl ring.
The formation of the various products arising from the
reactions of methyl acetoacetate with aryl hydrazines can
readily be envisaged in terms of an initial condensation to
form the acyclic (E)-hydrazone of type (A), exempli®ed here
Figure 2
A molecule of (II), showing the atom-labelling scheme and the intra-
molecular NÐHÁ Á ÁO hydrogen bond (dashed line). Displacement
ellipsoids are drawn at the 30% probability level.
Figure 3
A molecule of (III), showing the atom-labelling scheme. Displacement
ellipsoids are drawn at the 30% probability level.
Figure 4
A molecule of (V), showing the atom-labelling scheme. Displacement
ellipsoids are drawn at the 30% probability level.
ꢁ
Acta Cryst. (2007). C63, o462±o467
Wardell et al.
C11H13N3O4, C11H12N4O6, C10H10N2O and C13H13N3O3 o463

organic compounds
1
2
3
2
by compounds (I) and (II). Provided that hydrazine atom N1
is suf®ciently nucleophilic then the intermediate (B) can
readily cyclize, with loss of methanol, to form (C), whose
tautomer (D) is exempli®ed by (III). Intermediate (B) is
simply the Z isomer of (A) and its formation most plausibly
involves the tautomer (A0), in which effectively free rotation
about the N2ÐC13 bond is possible. Condensation of (C) with
carbonyl compounds yields the exo-methylene derivatives (E),
exempli®ed here by compound (V). We have noted above the
evidence for the signi®cance of polarized electronic forms in
(I) and (II), and an important consequence of such charge
separation is the reduction in nucleophilicity of atom N1 when
the aryl group contains 2-nitro and/or 4-nitro substituents. The
structural evidence from (I) and (II) is thus consistent with the
failure of these two compounds to undergo cyclization under
the reaction conditions that produce (III) and (IV). When
atom N1 is more nucleophilic, as in the presence of either an
unsubstituted phenyl ring or a 3-nitrophenyl ring, cyclization
to form (C) and (D) is thus feasible.
nitro atom O42 in the molecule at ( + x, y, 1 z), so
forming a C(6) chain running parallel to [100] and generated
3
1
by the 21 screw axis along (x, , ) (Fig. 6). In (III), hydroxy
4
2
atom O11 in the molecule at (x, y, z) acts as a hydrogen-bond
donor to pyrazole atom N2 in the molecule at (32 x, y, 21 + z),
so forming a C(5) chain running parallel to the [001] direction
and generated by the c-glide plane at x = 34 (Fig. 7). There are
no direction-speci®c interactions between the chains in
compounds (I) and (III), but those in (II) are weakly linked by
a dipolar carbonyl±nitro interaction. Carbonyl atom O12 in
Figure 5
Part of the crystal structure of (I), showing the formation of a hydrogen-
bonded chain along [010]. For the sake of clarity, H atoms bonded to the
C or N atoms not involved in the motif shown have been omitted. Atoms
marked with an asterisk (*) or a hash (#) are at the symmetry positions
(x, 1 + y, z) and (x, 1 + y, z), respectively.
While there are no direction-speci®c interactions of any
kind in the structure of (V), the molecules in (I), (II) and (III)
are all linked into chains; in each of (I) and (II), the chain is
built from a single CÐHÁ Á ÁO hydrogen bond, and that in (III)
by a single OÐHÁ Á ÁN hydrogen bond (Table 3). In (I),
methylene atom C12 in the molecule at (x, y, z) acts as a
hydrogen-bond donor to carbonyl atom O12 in the molecule
at (x, 1 + y, z), so generating by translation a C(4) (Bernstein
et al., 1995) chain running parallel to the [010] direction
(Fig. 5). In (II), the hydrogen-bond donor and acceptor are
both different from those utilized in (I). In (II), aryl atom C6
in the molecule at (x, y, z) acts as a hydrogen-bond donor to
Figure 6
Part of the crystal structure of (II), showing the formation of a hydrogen-
bonded chain along [100]. For the sake of clarity, H atoms bonded to the
C or N atoms not involved in the motif shown have been omitted. Atoms
marked with an asterisk (*) or a hash (#) are at the symmetry positions
1
2
3
2
3
2
(
+ x,
y, 1 z) and (12 + x,
y, 1 z), respectively.
ꢁ
o464 Wardell et al. C11H13N3O4, C11H12N4O6, C10H10N2O and C13H13N3O3
Acta Cryst. (2007). C63, o462±o467

organic compounds
from ethanol [m.p. 398±400 K; literature m.p. 400 K (Singh, 2005)].
IR (KBr, cm 1): 3130±2700, 1569, 1534. For the synthesis of (IV), a
solution of methyl acetoacetate (1 mmol) and 3-nitrophenyl-
hydrazine hydrochloride (1 mmol) in methanol (20 ml) was heated
under re¯ux for 30 min; the solution was cooled to ambient
temperature and then evaporated to dryness. The residue was
recrystallized from ethanol, but this material was not suitable for
single-crystal X-ray diffraction. IR (KBr, cm 1): 3120, 3100±2300,
1591, 1556, 1530. Further recrystallization of (IV) from acetone gave
(V). IR (KBr, cm 1): 1688, 1614, 1529.
Compound (I)
Crystal data
3
Ê
C11H13N3O4
Mr = 251.24
V = 1140.73 (7) A
Z = 4
Monoclinic, P21=n
Mo Kꢂ radiation
ꢃ = 0.11 mm
T = 120 (2) K
0.28 Â 0.22 Â 0.04 mm
1
Ê
a = 12.1494 (4) A
Figure 7
Ê
b = 5.1355 (2) A
Part of the crystal structure of (III), showing the formation of a hydrogen-
bonded chain along [001]. For the sake of clarity, H atoms bonded to the
C or N atoms not involved in the motif shown have been omitted. Atoms
marked with an asterisk (*) or a hash (#) are at the symmetry positions
Ê
c = 18.6969 (6) A
ꢁ = 102.079 (2)ꢀ
Data collection
3
1
1
(
x, y,
+ z) and (32 x, y, + z), respectively.
2
2
2
Bruker±Nonius KappaCCD
diffractometer
13943 measured re¯ections
2617 independent re¯ections
1931 re¯ections with I > 2ꢄ(I)
Rint = 0.053
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.975, Tmax = 0.995
the molecule at (x, y, z), which forms part of the hydrogen-
bonded chain along (x, 34, 21 ), makes a nearly linear contact with
nitro atom N12 in the molecule at ( 12 + x, y, 23 z), which lies
Re®nement
in the hydrogen-bonded chain along (x, 34, 1) [OÁ Á ÁNi =
R[F2 > 2ꢄ(F2)] = 0.045
wR(F2) = 0.117
S = 1.05
166 parameters
H-atom parameters constrained
i
ꢀ
Ê
2.885 (2) A and CÐOÁ Á ÁN = 173.7 (2) ; symmetry code: (i)
3
Ê
1
2
3
2
Áꢅmax = 0.26 e A
+ x, y,
[100] chains weakly into a sheet parallel to (010).
z], and the effect of this contact is to link the
3
Ê
0.29 e A
2617 re¯ections
Áꢅmin
=
The monoclinic polymorph of (III) (Bechtel et al., 1973a;
Chmutova et al., 2001) is, in fact, a 1:1 cocrystal of the two
tautomeric forms 5-hydroxy-3-methyl-1-phenylpyrazole and
3-methyl-1-phenyl-2H-pyrazolin-5-one, (IIIa), and the mol-
ecules are linked by alternating OÐHÁ Á ÁO and NÐHÁ Á ÁN
hydrogen bonds into C22(10) chains. By contrast, the sulfur
analogue of (II) exists in the crystalline state solely as the
thione tautomer (Chmutova et al., 2001). Isomeric with (III) is
3-hydroxy-5-methyl-1-phenylpyrazole, (VI), which exists in
the crystalline state as a single tautomer; the compound
crystallizes with Z0 = 2 in the space group Pbca and the mol-
ecules are linked by two independent OÐHÁ Á ÁN hydrogen
bonds into R22(8) dimers, which do not exhibit even approx-
imate symmetry (Bechtel et al., 1973b).
Compound (II)
Crystal data
3
Ê
C11H12N4O6
Mr = 296.25
V = 2653.7 (3) A
Z = 8
Orthorhombic, Pbca
Ê
Mo Kꢂ radiation
1
a = 10.6100 (3) A
ꢃ = 0.12 mm
T = 120 (2) K
Ê
b = 12.1878 (4) A
Ê
c = 20.522 (2) A
0.43 Â 0.35 Â 0.14 mm
Data collection
Bruker±Nonius KappaCCD
diffractometer
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.961, Tmax = 0.983
20035 measured re¯ections
3033 independent re¯ections
2289 re¯ections with I > 2ꢄ(I)
Rint = 0.061
Re®nement
R[F2 > 2ꢄ(F2)] = 0.044
wR(F2) = 0.116
S = 1.05
192 parameters
H-atom parameters constrained
Experimental
3
Ê
For the synthesis of (I), a solution of methyl acetoacetate (1 mmol)
and 2-nitrophenylhydrazine (1 mmol) in methanol (10 ml) was
heated under re¯ux for 30 min; the solution was cooled to ambient
temperature and then evaporated to dryness. The product, (I), was
recrystallized from ethanol. IR (KBr, cm 1): 3330, 1731, 1613, 1575.
Heating a solution of (I) in ethanol for 1 h at re¯ux temperature led
to no cyclization or other change. Compound (II) was similarly
prepared from methyl acetoacetate and 2,4-dinitrophenylhydrazine,
but the heating time was 90 min; compound (II) was recrystallized
from ethanol. IR (KBr, cm 1): 3327, 1740, 1620, 1594. Compound
(III) was prepared from the reaction of methyl acetoacetate and
phenylhydrazine, exactly as for (I). The product was recrystallized
Áꢅmax = 0.27 e A
3
Ê
0.25 e A
3033 re¯ections
Áꢅmin
=
Compound (III)
Crystal data
3
Ê
C10H10N2O
Mr = 174.20
Orthorhombic, Pca21
V = 870.29 (9) A
Z = 4
Mo Kꢂ radiation
1
Ê
a = 15.0138 (9) A
ꢃ = 0.09 mm
T = 120 (2) K
Ê
b = 5.2952 (3) A
Ê
c = 10.9469 (6) A
0.22 Â 0.09 Â 0.02 mm
ꢁ
Acta Cryst. (2007). C63, o462±o467
Wardell et al.
C11H13N3O4, C11H12N4O6, C10H10N2O and C13H13N3O3 o465

organic compounds
Data collection
Table 2
Selected bond lengths (A) for (III) and (V).
Ê
Bruker±Nonius KappaCCD
diffractometer
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.974, Tmax = 0.998
8739 measured re¯ections
1051 independent re¯ections
913 re¯ections with I > 2ꢄ(I)
Rint = 0.057
(III)
(V)
N1ÐN2
1.387 (3)
1.333 (3)
1.394 (3)
1.378 (3)
1.364 (3)
1.329 (3)
±
1.433 (3)
1.288 (3)
1.452 (3)
1.500 (3)
1.371 (3)
1.205 (3)
1.361 (3)
N2ÐC13
C13ÐC12
C12ÐC11
C11ÐN1
C11ÐO11
C12ÐC15
Re®nement
R[F2 > 2ꢄ(F2)] = 0.039
wR(F2) = 0.093
S = 1.12
1051 re¯ections
120 parameters
1 restraint
H-atom parameters constrained
3
Ê
Áꢅmax = 0.17 e A
3
Ê
0.21 e A
Áꢅmin
=
Table 3
Hydrogen bonds and short intramolecular contacts (A, ꢀ) for (I)±(III)
and (V).
Ê
Compound (V)
Crystal data
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
3
Ê
C13H13N3O3
Mr = 259.26
Monoclinic, P21=c
Ê
a = 8.8910 (3) A
V = 1198.17 (10) A
Z = 4
(I)
N1ÐH1Á Á ÁO21
0.88
0.99
1.97
2.42
2.6077 (19)
3.3894 (19)
128
166
Mo Kꢂ radiation
1
C12ÐH12AÁ Á ÁO12i
ꢃ = 0.11 mm
T = 120 (2) K
Ê
b = 10.1699 (6) A
(II)
N1ÐH1Á Á ÁO21
Ê
c = 13.4731 (7) A
0.36 Â 0.24 Â 0.14 mm
0.93
0.95
1.95
2.51
2.6258 (17)
3.293 (2)
128
139
ꢁ = 100.415 (3)ꢀ
C6ÐH6Á Á ÁO42ii
Data collection
(III)
O11ÐH11Á Á ÁN2iii
0.84
0.95
1.79
2.31
2.633 (3)
2.881 (3)
178
118
Bruker±Nonius KappaCCD
diffractometer
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
Tmin = 0.958, Tmax = 0.985
15923 measured re¯ections
2752 independent re¯ections
1840 re¯ections with I > 2ꢄ(I)
Rint = 0.057
C6ÐH6Á Á ÁO1
(V)
C6ÐH6Á Á ÁO1
0.95
2.24
2.871 (3)
123
1
2
3
y ‡
2
1
.
Symmetry codes: (i) x; y 1; z; (ii) x
;
;
z ‡ 1; (iii) x ‡ 32 ; y; z
2
Re®nement
R[F2 > 2ꢄ(F2)] = 0.060
wR(F2) = 0.165
S = 1.04
175 parameters
H-atom parameters constrained
successful structure analysis. All H atoms were located in difference
maps and then treated as riding atoms. H atoms bonded to C atoms
were placed in geometrically idealized positions and allowed to ride,
with CÐH distances of 0.95 (aromatic and pyrazole), 0.98 (CH3) or
3
Ê
Áꢅmax = 0.53 e A
3
Ê
0.27 e A
2752 re¯ections
Áꢅmin
=
Table 1
Selected bond distances and torsion angles (A, ) for (I) and (II).
Ê
0.99 A (CH2), and with Uiso(H) = kUeq(C), where k = 1.5 for the
ꢀ
Ê
methyl groups and k = 1.2 otherwise. H atoms bonded to N or O
atoms were allowed to ride at the distances deduced from difference
(I)
(II)
Ê
Ê
Ê
maps [NÐH = 0.88 A in (I) or 0.93 A in (II), and OÐH = 0.84 A, with
Uiso(H) = 1.2Ueq(N) or 1.5Ueq(O)]. In the absence of signi®cant
resonant scattering it was not possible to establish the correct
orientation of the structure of (III) with respect to the polar-axis
direction; accordingly, the Friedel-equivalent re¯ections were merged
prior to the ®nal re®nements. Compound (IV) has unit-cell dimen-
C1ÐC2
C2ÐC3
C3ÐC4
C4ÐC5
C5ÐC6
C6ÐC1
C1ÐN1
C2ÐN12
N12ÐO21
N12ÐO22
C4ÐN14
N14ÐO41
N14ÐO42
1.411 (2)
1.403 (2)
1.368 (3)
1.401 (2)
1.368 (2)
1.414 (2)
1.366 (2)
1.438 (2)
1.2482 (18)
1.2363 (17)
±
1.420 (2)
1.388 (2)
1.374 (2)
1.402 (2)
1.373 (2)
1.413 (2)
1.3612 (19)
1.4517 (19)
1.2394 (16)
1.2290 (16)
1.4503 (19)
1.2352 (17)
1.2378 (17)
Ê
Ê
Ê
sions a = 25.648 (4) A, b = 3.8259 (6) A, c = 24.790 (5) A and ꢁ =
118.739 (14)ꢀ in the space group P2/c; the compound was crystallized
0.5+
from ethanol as a hemihydrochloride salt, 2C10H9.5N3O3 ÁCl and
±
±
the crystals were twinned, as well as exhibiting very poor overall
quality.
For all compounds, data collection: COLLECT (Hooft, 1999); cell
re®nement: DENZO (Otwinowski & Minor, 1997) and COLLECT;
data reduction: DENZO and COLLECT; program(s) used to solve
structure: OSCAIL (McArdle, 2003) and SHELXS97 (Sheldrick,
1997); program(s) used to re®ne structure: OSCAIL and SHELXL97
(Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); soft-
ware used to prepare material for publication: SHELXL97 and
PRPKAPPA (Ferguson, 1999).
C2ÐC1ÐN1ÐN2
178.57 (14)
178.70 (15)
178.15 (13)
113.65 (17)
171.48 (13)
178.88 (13)
3.8 (2)
173.08 (13)
179.46 (14)
178.09 (13)
101.57 (17)
155.12 (14)
176.87 (16)
14.1 (2)
C1ÐN1ÐN2ÐC13
N1ÐN2ÐC13ÐC12
N2ÐC13ÐC12ÐC11
C13ÐC12ÐC11ÐO11
C12ÐC11ÐO11ÐC15
C1ÐC2ÐN12ÐO21
C3ÐC4ÐN14ÐO41
0.9 (2)
X-ray data were collected at the EPSRC National Crystal-
lography Service, University of Southampton, UK. The
authors thank the staff for all their help and advice. JLW
thanks CNPq and FAPERJ for ®nancial support.
For (I), (II) and (V), respectively, the space groups P21/n, Pbca and
P21/c were uniquely assigned from the systematic absences. For (III),
the systematic absences permitted Pca21 and Pbcm (= Pcam) as
possible space groups; Pca21 was selected and con®rmed by the
ꢁ
o466 Wardell et al. C11H13N3O4, C11H12N4O6, C10H10N2O and C13H13N3O3
Acta Cryst. (2007). C63, o462±o467

organic compounds
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C11H13N3O4, C11H12N4O6, C10H10N2O and C13H13N3O3 o467