organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
0
2
,2 -Methylenebis(3-hydroxy-5,5-
dimethylcyclohex-2-en-1-one)
a
b
c
c
John N. Low, ² Justo Cobo, Silvia Cruz, Jairo Quiroga
d
and Christopher Glidewell *
a
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen
b
AB24 3UE, Scotland, Departamento de Qu Âõ mica Inorg a nica y Org a nica,
c
Universidad de Ja e n, 23071 Ja e n, Spain, Grupo de Investigaci o n de Compuestos
Heteroc Âõ clicos, Departamento de Qu Âõ mica, Universidad de Valle, AA 25360, Cali,
d
Colombia, and School of Chemistry, University of St Andrews, St Andrews, Fife
KY16 9ST, Scotland
Received 13 October 2003
Accepted 17 October 2003
Online 8 November 2003
Figure 1
The two independent molecules of compound (II), showing the atom-
labelling scheme for (a) molecule 1 and (b) molecule 2. Displacement
ellipsoids are drawn at the 30% probability level. The symmetry codes are
as in Table 1.
The title compound, C H O , crystallizes with two indepen-
4
1
7
24
dent molecules, both lying across twofold rotation axes in
space group Pccn, in a unit cell whose dimensions closely
mimic those of a tetragonal cell. Each molecule contains
quently obtained in ca 70% yield by reaction of dimedone with
aqueous formaldehyde in a reaction analogous to that used for
the synthesis of compound (I) (SethuSankar et al., 2000).
Compound (II) crystallizes in the orthorhombic space group
Pccn; there are two independent molecules in the cell, each
Ê
paired OÐHÁ Á ÁO hydrogen bonds [HÁ Á ÁO = 1.81 and 1.83 A,
Ê
OÁ Á ÁO = 2.640 (2) and 2.642 (2) A, and OÐHÁ Á ÁO = 168 and
ꢀ
1
62 ].
Comment
0
lying across a twofold rotation axis, so that Z = 2 Â 0.5 = 1. In
0
The structure of 2,2 -methylenebis(3-hydroxy-2-cyclohexen-1-
one), (I), has recently been the subject of a brief report
the selected asymmetric unit, molecule 1, containing atom C1
3 1
4 4
(Fig. 1a), lies across the axis along ( , , z), while molecule 2,
(SethuSankar et al., 2000), although the molecular constitution
is incorrectly depicted in that report. This compound crystal-
lizes in space group Pbca, with Z = 1, and the molecular
structure is characterized by two rather short intramolecular
hydrogen bonds.
1 1
4
containing atom C2 (Fig. 1b), lies across the axis ( , , z). The
metric unit cell very closely mimics a tetragonal cell, with the a
Ê
and b repeat vectors differing by only ca 0.002 A. However,
the re®ned structure is clearly orthorhombic, although subject
to twinning across the (110) plane; a search for possible
additional symmetry revealed none, and the arrangement of
the molecules in the unit cell (Fig. 2) clearly rules out the
possibility of any kind of fourfold axis.
4
0
The two independent molecules are both chiral, with C2
molecular symmetry, but the space group ensures that for each
there are equal numbers of the two enantiomorphs present in
the crystal. The two molecules in the selected asymmetric unit
are in fact of opposite hand, as shown qualitatively by their
overall con®gurations (Fig. 1) and quantitatively both by the
key torsion angles (Table 1) and, better, by the ring-puckering
parameters. For the independent rings C11±C16 and C21±C26,
the overall puckering amplitudes Q (Cremer & Pople, 1975)
are identical within experimental uncertainty, viz. 0.457 (3)
We report here the structure of a tetramethyl analogue of
0
(
I), namely 2,2 -methylenebis(3-hydroxy-5,5-dimethylcyclo-
hex-2-en-1-one), (II), originally obtained in low yield as an
unexpected by-product of a three-component reaction
between 4-amino-2-methoxypyrimidin-6(1H)-one, form-
aldehyde and 5,5-dimethylcyclohexane-1,3-dione (dimedone),
which had been intended to produce a tricyclic octahydro-
pyrimido[3,4-b]quinoline system. Compound (II) was subse-
Ê
and 0.459 (3) A, respectively, but for the atom sequences Cn1
ꢀ
to Cn6 (n = 1 or 2), the ꢀ values are 59.0 (3) and 119.8 (3) ,
respectively, and the supplementary nature of these values
de®nes different absolute con®gurations for the two molecules
(Boeyens, 1978). The ' values, based on the same atom
² Postal address: Department of Electrical Engineering and Physics,
University of Dundee, Dundee DD1 4HN, Scotland.
o666 # 2003 International Union of Crystallography
DOI: 10.1107/S0108270103023606
Acta Cryst. (2003). C59, o666±o668