organic compounds
sites; Fig. 3) coincides with a crystallographic twofold axis.
Consequently, the six-membered C1±C6 and C18±C13 rings of
the other molecules are now related by symmetry, as shown in
Fig. 3, and atoms N1, O1 and H1 are distributed over pairs of
sites, all of occupancy 0.5 (only one member of each pair is
shown). For convenience, the individual molecules are
denoted (I), (IIA), (IIB) and (IIC).
Bond lengths and angles for the benzisoxazole residue
comprising atoms O1, N1 and C1±C7 and the torsion angles
involving the C7ÐC8 bonds of all four molecules are given in
Table 2. Ignoring for the moment the torsion angles, which are
discussed later, the bond lengths and angles are similar in all
four molecules and are entirely consistent with the distribu-
tion of single and double bonds indicated in the chemical
structural drawings of (I) and (II). Agreement is particularly
good for molecules (I) and (IIA), but less so for (IIC) and
especially (IIB), in which the crystallographically induced
pseudosymmetry and disorder noted above are seen to have a
deleterious effect.
All of the molecules consist of two essentially planar frag-
ments, namely the benzisoxazole residue discussed above and
the substituent phenyl ring [C8±C13 or its equivalent in mol-
ecule (IIB)]. In all four cases, these fragments are related by
rotation about the C7ÐC8 bond joining them [or its equiva-
lent in molecule (IIB)] by angles (computed from the relevant
Figure 4
Aview of the unit cell of (I), in the same representation as in Fig. 1 except
that all H atoms other than those involved in hydrogen-bond (dashed
lines) formation have been omitted and only selected atoms are labelled.
1
1
2
The view is along a. [Symmetry codes: (iii) x, y � 1, z; (iv) � x, + y, � z;
2
1
2
1
2
1
2
1
2
1
2
1
(
1
2
v) � x, y � , � z; (vi) � x, 1 � y, + z; (vii) � x, 2 � y, + z; (viii)
1 1 3
+
2 2 2
2
x, � y, 1 � z; (ix) + x, � y, 1 � z.]
A feature of the packing of the molecules in the cell of (I)
(
Fig. 4) is the presence of O2ÐH2Á Á ÁN1 and ancilliary C10Ð
H10Á Á ÁO1 hydrogen bonds (Table 1). These connect the
molecules into chains propagated in the b direction, in which
adjacent molecules within the chain are related by cell trans-
lation. No equivalent intermolecular interaction is observed in
torsion angles; Table 2) of 53.02 (14), 12.58 (15), 12.3 (2) and
ꢀ
8
.4 (8) for molecules (I), (IIA), (IIB) and (IIC), respectively.
These rotations can occur in either a clockwise or an anti-
clockwise sense and consequently render the molecules
handed. In the non-centrosymmetric structure of (I), where
the twist is greatest, probably because of the steric require-
ment of the o-methoxy substituents, all of the molecules in a
given crystal are of the same hand, while crystals of opposite
hand are presumably present in the bulk sample. In the
absence of atoms of atomic number higher than that of
oxygen, the absolute structure is, however, indeterminate. The
centrosymmetric structure of (II), in which the twist is much
smaller, is of course racemic.
(II).
Compounds (I) and (II) have also been characterized to
1
some extent by spectroscopy (see below). Thus, while the H
NMR spectrum of (II) shows only multiple aryl H-atom
chemical shifts, that of (I) can be analysed more speci®cally,
with the alkoxy groups being seen to bring the resonances of
the H atoms adjacent to them up-®eld (to ꢀ = 6.19 and
6
.28 p.p.m.). Mass spectral fragmentation is also consistent
with previous observations (Dyall & Karpa, 1989) that loss of
CO and HCN is coupled to C H N, C H N and C H NO
fragments, which are also found in the spectrum of (I). Frag-
mentation of (II) shows a pattern similar to that of (I).
7
4
7
5
7
4
The phenol residue of (I) merits further comment. The
substituent atoms O2±O4 are not signi®cantly displaced from
the plane de®ned by the C8±C13 ring nucleus, and neither is
atom C7. The displacement of the methyl C14 group is only
Ê
Experimental
0
0
.027 (6) A, while that of atom C15 is much greater at
Ê
.327 (5) A.
Crystals of (I) were obtained in a manner similar to that described for
(III) by Forrester et al. (1992). Zinc dust (1.0 g) was added in portions
over a period of 2 h to a stirred mixture of 2 -nitro-4,6-dimethoxy-2-
0
hydroxybenzophenone, (Ia) (1.0 g), in ethanol (200 ml) and NH
(1.0 g) in water (10 ml). After stirring overnight at room temperature,
4
Cl
work-up in the usual manner yielded 813 mg of solid in the form of a
mixture of products. The solid was dissolved in ethyl acetate and the
components were separated by preparative thin-layer chromato-
graphy (TLC), with silica gel as the stationary phase and ethyl
acetate/benzene as eluant. Two comparatively immobile phases
(minor components) were not isolated. The most mobile phase,
eluted with EtOAc/benzene in a 2:1 ratio, was the aniline (Ib),
resulting from complete reduction of the nitro group of the original
benzophenone. The fraction containing (I), the major component,
which constituted approximately 75% by weight of the total solids
Figure 3
A view of molecule B of (II). The representation is the same as in Fig. 1.
3
[
Symmetry code: (i) � x, y, 2 � z.]
ꢁ
Acta Cryst. (2003). C59, o516±o519
R. Alan Howie et al.
C
15
H13NO
4
and C13
9
H NO o517
Howie
