Hydrogen-bonding patterns in enamino-nes: (2Z)-1-(4-bromophenyl)-2- (pyrrolidin-2-ylidene)ethanone and its piperidin-2-ylidene and azepan-2-ylidene analogues

Article abstract of DOI:10.1107/S0108270107053206

The title compounds, namely (2Z)-1-(4-bromo-phenyl)-2-(pyrrolidin-2-yl- idene)ethanone, C12H12BrNO, (I), (2Z)-1-(4-bromo-phenyl)-2-(piperidin-2-yl- idene)ethanone, C13H14BrNO, (II), and (2Z)-2-(azepan-2-yl-idene)-1-(4-bromo- phenyl)-ethan-one, C14H16BrNO,

Full text of DOI:10.1107/S0108270107053206

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
(Michael et al., 1999). We have recently observed discre-
pancies in the reactivity of N-heterocyclic enaminones of
different ring sizes (Michael et al., 2001, 2002). The present
investigation was undertaken in order to ascertain whether
there might be underlying structural differences in the
conjugated enaminone system as the size of the ring
containing the N atom is varied. The three title compounds,
(I)±(III), were selected as models to probe possible structural
differences, in view of their ready preparation by the
Eschenmoser sul®de contraction method (Roth et al., 1971).
It was found that the bond lengths and angles for the
conjugated and essentially planar enaminone core (NÐ
ISSN 0108-2701
Hydrogen-bonding patterns in
enaminones: (2Z)-1-(4-bromophenyl)-
2-(pyrrolidin-2-ylidene)ethanone and
its piperidin-2-ylidene and azepan-2-
ylidene analogues
James L. Balderson, Manuel A. Fernandes, Joseph P.
Michael* and Christopher B. Perry
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand,
PO Wits 2050, Johannesburg, South Africa
Correspondence e-mail: joseph.michael@wits.ac.za
Received 7 September 2007
Accepted 25 October 2007
Online 24 November 2007
Figure 1
The molecular structure of (I), showing the atomic numbering scheme.
Displacement ellipsoids are drawn at the 50% probability level and H
atoms are shown as small spheres of arbitrary radii. The intramolecular
hydrogen bond between atoms O1 and H1 is shown as a dotted bond.
The title compounds, namely (2Z)-1-(4-bromophenyl)-2-
(pyrrolidin-2-ylidene)ethanone, C12H12BrNO, (I), (2Z)-1-(4-
bromophenyl)-2-(piperidin-2-ylidene)ethanone, C13H14BrNO,
(II), and (2Z)-2-(azepan-2-ylidene)-1-(4-bromophenyl)ethan-
one, C14H16BrNO, (III), are characterized by bifurcated intra-
and intermolecular hydrogen bonding between the secondary
amine and carbonyl groups. The former establishes a six-
membered hydrogen-bonded ring, while the latter leads to the
formation of centrosymmetric dimers. Weak CÐHÁ Á ÁBr
interactions link the individual molecules into chains that
run along the [011], [101] and [101] directions in (I)±(III),
respectively. Additional weak BrÁ Á ÁO, CÐHÁ Á Áꢀ and CÐ
HÁ Á ÁO interactions further stabilize the crystal structures.
Figure 2
Comment
The molecular structure of (II), showing the atomic numbering scheme.
Displacement ellipsoids are drawn at the 50% probability level and H
atoms are shown as small spheres of arbitrary radii. The intramolecular
hydrogen bond between atoms O1 and H1 is shown as a dotted bond.
Enaminones (ꢁ-acylated enamines) are valuable inter-
mediates for the synthesis of alkaloids and other nitrogen-
containing heterocycles (Stanovnik & Svete, 2004; Cheng et
Figure 3
The molecular structure of (III), showing the atomic numbering scheme.
Displacement ellipsoids are drawn at the 50% probability level and H
atoms are shown as small spheres of arbitrary radii. The intramolecular
hydrogen bond between atoms O1 and H1 is shown as a dotted bond.
al., 2004; Negri et al., 2004; Elliott et al., 2006). These versatile
systems play a pivotal role in our own research programme
o734 # 2007 International Union of Crystallography
DOI: 10.1107/S0108270107053206
Acta Cryst. (2007). C63, o734±o738

organic compounds
C
CÐC O) of the three compounds (Figs. 1±3) proved to
comparable intermolecular hydrogen bond is from atom N1 to
y, 1
respectively. This intermolecular hydrogen bonding leads to
the formation of dimers described by the R22(12) graph-set
motif.
In the crystal structures of each compound, there is also a
weak CÐHÁ Á ÁBr interaction (Figs. 4±6) that links the mol-
ecules together into chains along the [011], [101] and [101]
directions in compounds (I), (II) and (III), respectively. The
CÐHÁ Á ÁBr hydrogen-bond geometries (Tables 1±3) are
be effectively the same and within the expected ranges (Allen
et al., 1987). More interesting, however, are their packing
arrangements. Compounds (I)±(III) are characterized by
bifurcated hydrogen bonds (one intramolecular and one
intermolecular) between the secondary amine and carbonyl
groups. The intramolecular NÐHÁ Á ÁO hydrogen bond
between the donor atom N1 and the acceptor atom O1 can be
described by the graph-set motif S(6) (Etter et al., 1990;
Bernstein et al., 1995). In compound (I), atom N1 also acts as
an intermolecular hydrogen-bond donor via atom H1 to atom
O1 at (2 x, 1 y, z). For compounds (II) and (III), the
atom O1 at (2
x, y, 1
z) and (1
x, 1
z),
Figure 5
(a) Part of the crystal structure of (II), showing the formation of
hydrogen-bonded dimers by intermolecular NÐHÁ Á ÁO and CÐHÁ Á ÁO
interactions. The molecules are linked together into chains along [101] by
weak CÐHÁ Á ÁBr interactions. (b) An alternative view of (II), showing the
formation of intramolecular S(6), intermolecular R22(12) and inter-
molecular R22(14) rings built from NÐHÁ Á ÁO and weak CÐHÁ Á ÁO
interactions. In both views, molecules A, B, C, D, E and F are at the
symmetry positions (x, y, z), ( 1 + x, y, 1 + z), (2 x, y, 1 z), (1 + x, y,
1 + z), ( 1 + x, y, z) and (2 x, 1 y, 1 z), respectively.
Figure 4
(a) Bifurcated NÐHÁ Á ÁO hydrogen bonding and weak CÐHÁ Á ÁBr and
BrÁ Á ÁO interactions in the structure of (I). (b) An alternative view of (I),
showing the weak CÐHÁ Á Áꢀ and weak CÐHÁ Á ÁO interactions. In both
views, molecules A, B, C, D, E and F are at the symmetry positions (x, y,
z), (32 x, 12 + y, 21 z), (2 x, 1 y, z), ( 21 + x, 21 y, 21 + z), (1 + x, y, z)
and (2 x, 1 y, 1 z), respectively.
ꢀ
Acta Cryst. (2007). C63, o734±o738
Balderson et al.
C12H12BrNO, C13H14BrNO and C14H16BrNO o735

organic compounds
comparable with values reported in the literature (Ponnus-
wamy & Sony, 2006).
HÁ Á ÁOi and CÐHÁ Á ÁCgi interactions [Cg is the centroid of the
C9±C14 ring; symmetry code: (i) 1 x, 12 + y, 23 z] that link
molecules together into chains along the [011] direction
(Fig. 6). In this structure, the seven-membered ring has a total
In addition to CÐHÁ Á ÁBr interactions in compound (I), the
chains of molecules extending along the [011] direction are
=
further stabilized by BrÁ Á ÁO interactions [Br1Á Á ÁO1i
puckering amplitude Q of 0.7524 (17) A.
Ê
i
i
i
ꢁ
Ê
3.161 (2) A, C10ÐBr1Á Á ÁO1 = 165.39 (7) and C1 ÐO1 Á Á Á
Br1 = 98.2 (1)ꢁ; symmetry code: (i) 21 + x, 21 y, 21 + z] (Fig. 4).
These values compare favourably with those obtained from a
study of short OÁ Á Áhalogen interactions in biological mol-
ecules (Auf®nger et al., 2004). The crystal structure of (I) also
contains a weak CÐHÁ Á ÁCg intermolecular interaction that
extends along the [001] direction, where Cg is the centroid of
the C7±C12 benzene ring. The pyrrolidine ring has an
envelope conformation with atom C5 at the ¯ap. The Cremer
& Pople puckering parameters (Cremer & Pople, 1975) for this
Experimental
The syntheses of compounds (I)±(III) were adapted from the
procedure described by Roth et al. (1971) for the preparation of (I).
4-Bromophenacyl bromide (1.05 equivalents) was added to a solution
of the appropriate thiolactam [pyrrolidine-2-thione, piperidine-2-
thione or azepane-2-thione; 1.0 equivalent; cf. Curphey (2002)] in
CHCl3 (5 ml per mmol). After 30 min at room temperature, the
solvent was removed on a rotary evaporator. The resulting mixture
was kept at room temperature for 48 h to ensure that the reaction
went to completion. The resulting solid was partitioned between
CH2Cl2 and aqueous saturated K2CO3 solution. The organic phase
was separated off and the aqueous phase was extracted with a further
portion of CH2Cl2. The combined organic extracts were dried
(MgSO4) and evaporated to yield the crude S-alkylated intermediate.
This was dissolved in dry CHCl3 (10 ml per mmol) to which
triphenylphosphine (2 equivalents) was added. The solution was
heated under re¯ux for 24 h, after which the solvent was evaporated.
The crude enaminone product was puri®ed by chromatography on
silica gel with dichloromethane as eluant, followed by ethyl acetate±
hexane (2:3), to afford the desired products, (I)±(III).
ꢁ
Ê
molecule are q2 = 0.264 (2) A and '2 = 113.8 (4) .
The hydrogen-bonded dimers in compound (II) are further
reinforced by a weak CÐHÁ Á ÁO interaction between atom
H7A and atom O1 at (2 x, y, 1 z), producing a motif
described by the graph set R22(12). A second set of CÐHÁ Á ÁO
interactions, occurring between atom H5 and atom O1 at
(2 x, 1 y, 1 z), gives rise to another set of intermolecular
bonded dimers described by the R22(14) graph set (Fig. 5). In
this structure, the piperidine ring adopts a half-chair confor-
ꢁ
Ê
mation [puckering amplitude QT = 0.483 (3) A, ꢂ = 136.7 (4)
and ' = 26.9 (5)ꢁ].
In addition to the NÐHÁ Á ÁO and CÐHÁ Á ÁBr interactions
For compound (I), yield 66%; m.p. 443±446 K [literature m.p. 446±
447 K (Roth et al., 1971)]. 1H NMR (300 MHz, CDCl3, Me4Si): ꢃ 2.00±
2.10 (2H, m, 5-H), 2.74 (2H, m, 4-H), 3.66 (2H, m, 6-H), 5.75 (1H, s,
2-H), 7.52 and 7.74 (4H, 2 Â m, 8-H, 9-H, 11-H, 12-H), 10.28 (1H, s,
NH); 13C NMR (75 MHz, CDCl3, Me4Si): ꢃ 186.4 (C O), 170.0 (C3),
138.9 (C7), 131.3 and 128.7 (C8, C9, C11, C12), 125.1 (C10), 85.9 (C2),
47.9 (C6), 33.0 (C4), 21.3 (C5).
discussed earlier, the structure of (III) also contains CÐ
For compound (II), yield 55%; m.p. 388±390 K. 1H NMR
(300 MHz, CDCl3, Me4Si): ꢃ 1.76±1.88 (4H, m, 5-H and 6-H), 2.50
(2H, t, 4-H), 3.40 (2H, t, 7-H), 5.51 (1H, s, 2-H), 7.50 and 7.71 (4H,
2 Â d, J = 8.2 Hz, 9-H, 10-H, 12-H, 13-H), 11.70 (1H, s, NH); 13C NMR
(75 MHz, CDCl3, Me4Si): ꢃ 185.9 (C O), 166.6 (C3), 139.9 (C8),
131.6 and 128.8 (C9, C10, C12, C13), 125.0 (C11), 90.5 (C2), 41.6 (C7),
29.3 (C4), 22.5 and 19.6 (C5, C6). HRMS (EI), found: 281.0216;
C13H1481BrNO requires: 281.0238.
For compound (III), yield 76%; m.p. 418±421 K. 1H NMR
(300 MHz, CDCl3, Me4Si): ꢃ 1.68±1.77 (6H, m, 5-H, 6-H, and 7-H),
2.44 (2H, m, 4-H), 3.43 (2H, d, 8-H), 5.61 (1H, s, 2-H), 7.51 and 7.73
(4H, 2 Â m, 10-H, 11-H, 13-H, and 14-H), 11.54 (1H, s, NH); 13C
NMR (75 MHz, CDCl3, Me4Si): ꢃ 186.6 (C O), 171.8 (C3), 139.4
(C9), 128.5 and 131.3 (C10, C11, C13, C14), 124.9 (C12), 90.8 (C2),
44.5 (C8), 35.4, 30.6, 29.2 and 25.7 (C4, C5, C6, C7). HRMS (EI),
found: 295.0402; C14H1681BrNO requires: 295.0395.
Compound (I)
Crystal data
Figure 6
3
Part of the crystal structure of (III), showing the intra- and intermolecular
NÐHÁ Á ÁO hydrogen-bonding pattern. Chains of molecules are linked
together along the [101] direction by weak CÐHÁ Á ÁBr interactions, and
along the [011] direction by weak CÐHÁ Á Áꢀ and weak CÐHÁ Á ÁO
interactions. Molecules A, B, C, D, E and F are at the symmetry positions
Ê
C12H12BrNO
Mr = 266.14
Monoclinic, P21=n
Ê
a = 5.6636 (3) A
b = 18.9255 (9) A
V = 1074.42 (9) A
Z = 4
Mo Kꢄ radiation
1
ꢅ = 3.80 mm
T = 173 (2) K
Ê
Ê
1
1
3
2
1
(x, y, z), (1 + x,
(
y,
+ z), (1 x, 1 y, 1 z), (x,
3
y,
+ z),
2
c = 10.0500 (5) A
ꢁ = 94.1360 (10)ꢁ
0.37 Â 0.30 Â 0.20 mm
2
1 + x, 12 y, 122+ z) and (1 x,
+ y,
z), respectively.
1
2
2
ꢀ
o736 Balderson et al.
C12H12BrNO, C13H14BrNO and C14H16BrNO
Acta Cryst. (2007). C63, o734±o738

organic compounds
Data collection
Compound (III)
Bruker APEXII CCD area-detector
diffractometer
Absorption correction: multi-scan
[SADABS in SAINT-NT
(Bruker, 2005); ratio of minimum
to maximum apparent transmis-
sion = 0.688943; for Tmin below,
Tmin = Tmax  min-to-max ratio]
Tmin = 0.334, Tmax = 0.517
(expected range = 0.302±0.468)
9815 measured re¯ections
2595 independent re¯ections
2307 re¯ections with I > 2ꢆ(I)
Rint = 0.020
Crystal data
3
Ê
V = 1287.58 (6) A
C14H16BrNO
Mr = 294.19
Z = 4
Mo Kꢄ radiation
Monoclinic, P21=c
1
Ê
a = 12.2867 (3) A
ꢅ = 3.18 mm
T = 173 (2) K
Ê
b = 8.2416 (2) A
Ê
c = 12.9404 (4) A
0.49 Â 0.44 Â 0.15 mm
ꢁ = 100.702 (2)ꢁ
Re®nement
R[F2 > 2ꢆ(F2)] = 0.024
wR(F2) = 0.068
S = 1.06
2595 re¯ections
140 parameters
H atoms treated by a mixture of
independent and constrained
re®nement
Data collection
Bruker APEXII CCD area-detector
diffractometer
Absorption correction: integration
[face-indexed using XPREP in
SAINT-NT (Bruker, 2005)]
Tmin = 0.305, Tmax = 0.647
9654 measured re¯ections
3103 independent re¯ections
2401 re¯ections with I > 2ꢆ(I)
Rint = 0.043
3
Ê
Áꢇmax = 0.52 e A
3
Ê
0.60 e A
Áꢇmin
=
Table 1
Hydrogen-bond geometry (A, ) for (I).
ꢁ
Ê
Re®nement
Cg is the centroid of the C7±C12 benzene ring.
R[F2 > 2ꢆ(F2)] = 0.025
wR(F2) = 0.065
S = 1.02
3103 re¯ections
158 parameters
H atoms treated by a mixture of
independent and constrained
re®nement
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
3
Ê
N1ÐH1Á Á ÁO1
0.79 (2)
0.79 (2)
0.99
0.99
0.99
2.25 (2)
2.30 (2)
2.72
2.71
2.97
2.798 (2)
2.9124 (19)
3.524 (3)
3.679 (2)
3.701 (2)
128 (2)
136 (2)
139
166
132
Áꢇmax = 0.45 e A
N1ÐH1Á Á ÁO1i
C6ÐH6BÁ Á ÁO1ii
C4ÐH4BÁ Á ÁCgiii
C6ÐH6AÁ Á ÁBr1iv
Ê
0.41 e A
3
Áꢇmin
=
Table 3
Hydrogen-bond and weak intermolecular interaction geometry (A, ) for
(III).
ꢁ
Ê
Symmetry codes: (i) x ‡ 2; y ‡ 1; z; (ii) x ‡ 1; y; z; (iii) x ‡ 2; y ‡ 1; z ‡ 1;
(iv) x ‡ 32; y ‡ 21; z ‡ 12.
Cg is the centroid of the C9±C14 benzene ring.
Compound (II)
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
Crystal data
N1ÐH1Á Á ÁO1
0.811 (19)
0.811 (19)
0.95
0.99
0.99
2.057 (19)
2.467 (19)
2.59
2.67
2.95
2.6841 (18)
3.0757 (17)
3.439 (2)
3.5996 (17)
3.6838 (18)
134.0 (17)
132.7 (17)
149
157
131
C13H14BrNO
Mr = 280.16
Triclinic, P1
a = 6.9303 (2) A
Ê
b = 7.6280 (2) A
ꢈ = 102.189 (2)ꢁ
3
N1ÐH1Á Á ÁO1i
C10ÐH10Á Á ÁO1ii
C4ÐH4BÁ Á ÁCgii
C7ÐH7AÁ Á ÁBr1iii
Ê
V = 602.64 (3) A
Z = 2
Ê
Mo Kꢄ radiation
1
ꢅ = 3.39 mm
T = 173 (2) K
1
2
Symmetry codes: (i) x ‡ 1; y ‡ 1; z ‡ 1; (ii) x ‡ 1; y
;
z ‡ 32; (iii) x ‡ 1,
Ê
c = 12.1060 (3) A
ꢄ = 99.844 (2)ꢁ
y ‡ 12, z
.
1
2
0.49 Â 0.19 Â 0.17 mm
ꢁ = 99.5450 (10)ꢁ
Data collection
For all three title compounds, with the exception of atoms H1, all
H atoms were positioned geometrically and allowed to ride on their
parent atoms, with CÐH bond lengths of 0.95 (aromatic), 0.99 (CH2)
Bruker APEXII CCD area-detector
diffractometer
Absorption correction: integration
[face-indexed using XPREP in
SAINT-NT (Bruker, 2005)]
Tmin = 0.380, Tmax = 0.593
7739 measured re¯ections
2903 independent re¯ections
2387 re¯ections with I > 2ꢆ(I)
Rint = 0.033
Ê
or 0.98 A (CH3). Isotropic displacement parameters for these atoms
were set equal to 1.2 (aromatic and CH2) or 1.5 (CH3) times Ueq of
the parent atom. Atoms H1 were found in difference Fourier maps
and re®ned freely.
Re®nement
For all three compounds, data collection: APEX2 (Bruker, 2005);
cell re®nement: APEX2; data reduction: SAINT-NT (Bruker, 2005);
program(s) used to solve structure: SHELXS97 (Sheldrick, 1997);
program(s) used to re®ne structure: SHELXL97 (Sheldrick, 1997);
molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and
DIAMOND (Brandenburg, 1999); software used to prepare material
for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2003).
R[F2 > 2ꢆ(F2)] = 0.027
wR(F2) = 0.107
S = 1.14
2903 re¯ections
149 parameters
H atoms treated by a mixture of
independent and constrained
re®nement
3
Ê
Áꢇmax = 0.52 e A
3
Ê
0.36 e A
Áꢇmin
=
Table 2
Hydrogen-bond and weak intermolecular interaction geometry (A, ) for
(II).
ꢁ
Ê
This work was supported by the National Research Foun-
dation, Pretoria (NRF, GUN 2053652), and the University of
the Witwatersrand.
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
N1ÐH1Á Á ÁO1
0.82 (4)
0.82 (4)
0.99
0.99
0.95
2.17 (4)
2.55 (4)
2.63
2.58
2.40
2.656 (3)
3.168 (3)
3.609 (3)
3.297 (4)
3.194 (3)
3.894 (3)
118 (3)
133 (3)
172
129
141
N1ÐH1Á Á ÁO1i
C5ÐH5BÁ Á ÁO1ii
C7ÐH7AÁ Á ÁO1i
C10ÐH10Á Á ÁO1iii
C6ÐH6AÁ Á ÁBr1iv
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: AV3112). Services for accessing these data are
described at the back of the journal.
0.99
3.05
144
Symmetry codes: (i) x ‡ 2; y; z ‡ 1; (ii) x ‡ 2; y ‡ 1; z ‡ 1; (iii) x 1; y; z;
(iv) x ‡ 1; y; z 1.
ꢀ
Acta Cryst. (2007). C63, o734±o738
Balderson et al.
C12H12BrNO, C13H14BrNO and C14H16BrNO o737

organic compounds
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.
References
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837±838.
Michael, J. P., de Koning, C. B., Gravestock, D., Hosken, G. D., Howard, A. S.,
Jungmann, C. M., Krause, R. W. M., Parsons, A. S., Pelly, S. C. & Stanbury,
T. V. (1999). Pure Appl. Chem. 71, 979±988.
Michael, J. P., de Koning, C. B., San Fat, C. & Nattrass, G. L. (2002). Arkivoc, 9,
62±77.
Michael, J. P., de Koning, C. B. & van der Westhuyzen, C. W. (2001). J. Chem.
Soc. Perkin Trans. 1, pp. 2055±2062.
Negri, G., Kascheres, C. & Kascheres, A. J. (2004). J. Heterocycl. Chem. 41,
461±491.
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor,
R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1±19.
Auf®nger, P., Hays, F. A., Westhof, E. & Shing Ho, P. (2004). Proc. Natl Acad.
Sci. USA, 101, 16789±16794.
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem.
Int. Ed. Engl. 34, 1555±1573.
Brandenburg, K. (1999). DIAMOND. Version 2.1c. Crystal Impact GbR,
Bonn, Germany.
Bruker (2005). APEX2 (Version 2.0-1) and SAINT-NT (Version 6.0; includes
XPREP and SADABS). Bruker AXS Inc., Madison, Wisconsin, USA.
Cheng, Y., Huang, Z.-T. & Wang, M.-X. (2004). Curr. Org. Chem. 8, 325±
351.
Ponnuswamy, M. N. & Sony, S. M. M. (2006). Bull. Chem. Soc. Jpn, 11, 1766±
1772.
È
Roth, M., Dubs, P., Gotschi, E. & Eschenmoser, A. (1971). Helv. Chim. Acta,
Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354±1358.
Curphey, T. J. (2002). J. Org. Chem. 67, 6461±6473.
Elliott, M. C., Wood, J. L. & Wordingham, S. V. (2006). Trends Heterocycl.
Chem. 10, 73±95.
54, 710±734.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of
Gottingen, Germany.
È
Spek, A. L. (2003). J. Appl. Cryst. 36, 7±13.
Stanovnik, B. & Svete, J. (2004). Chem. Rev. 104, 2433±2480.
Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256±262.
ꢀ
o738 Balderson et al.
C12H12BrNO, C13H14BrNO and C14H16BrNO
Acta Cryst. (2007). C63, o734±o738