organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Ê
1.355 A; Allen et al., 1987) for bonds of type C(aryl)ÐNH ,
2
(
where N is planar. In contrast to the CÐC bonds, the C2ÐN3
and N3ÐC4 bonds have distances typical of those for loca-
lized double and single bonds of these types. While the C6Ð
O6 distance is typical of those in unstrained amides, the C6Ð
ISSN 0108-2701
Ê
N1 distance is very long for its type (mean value 1.346 A;
4
6
2
-Amino-5-(2-hydroxy-4,4-dimethyl-
-oxocyclohexenylmethyl)-1-methyl-
-(methylsulfanyl)pyrimidin-6(1H)-
Allen et al., 1987). These values, taken together, point to the
signi®cance of the polar form (Ia) as an important contributor
to the overall molecular±electronic structure but effectively
eliminate as contributors other forms, such as (Ib) and (Ic).
one: hydrogen-bonded chains are
p-stacked in pairs
a
b
c
d
John N. Low, ³ Justo Cobo, Silvia Cruz, Jairo Quiroga
e
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, Departamento de Qu Âõ mica, Universidad de
d
Nari Än o, Ciudad Universitaria, Torobajo, AA 1175 Pasto, Colombia, Grupo de
Investigaci o n de Compuestos Heteroc Âõ clicos, Departamento de Qu Âõ mica,
e
Universidad de Valle, AA 25360 Cali, Colombia, and School of Chemistry,
University of St Andrews, Fife KY16 9ST, Scotland
Received 13 January 2004
Accepted 15 January 2004
Online 10 February 2004
Molecules of the title compound, C H N O S, have a
3
1
5
21
3
markedly polarized electronic structure; the carbocyclic ring
adopts an envelope conformation and the overall molecular
conformation appears to be controlled by two intramolecular
hydrogen bonds, one each of the OÐHÁ Á ÁO and NÐHÁ Á ÁO
types. The molecules are linked into C(6) chains by an
intermolecular NÐHÁ Á ÁO hydrogen bond, and pairs of these
hydrogen-bonded chains are linked by a ꢀ±ꢀ stacking inter-
action.
There is clear evidence for bond ®xation in the atom
sequence between O52 and O56. Within the carbocyclic ring,
Ê
the total puckering amplitude, Q, is 0.455 (2) A, markedly less
Ê
than the value (0.63 A) for an ideal cyclohexane chair of 3m
Ê
(D3d) molecular symmetry, with CÐC distances of 1.54 A
(Cremer & Pople, 1975). For the atom sequence C51 to C56,
ꢀ
ꢀ
the angular parameters [ꢁ = 53.9 (3) and ' = 195.8 (4) ] are
clearly indicative of the sofa or envelope conformation being
the best single qualitative descriptor, with a local pseudo-
mirror plane passing through atoms C5, C54, C541 and C542
Comment
As part of a program for the synthesis of fused pyrimido
derivatives, we have investigated the three-component cyclo-
condensation between 4-amino-1-methyl-2-(methylsulfanyl)-
pyrimidin-6(1H)-one, formaldehyde and 5,5-dimethylcyclo-
hexane-1,3-dione (dimedone), but instead of the desired
pyrimido[3,4-b]quinoline, the intermediate title compound,
(Fig. 1); this conformation is con®rmed by the leading torsion
angles involving this ring (Table 1). However, the envelope
conformation can itself be represented as a linear combination
of the three primitive forms chair, boat and twist-boat (Evans
&
Boeyens, 1989), with the chair form dominant here.
There are three hydrogen bonds (Table 2), two of which are
(
I), was obtained. We report here its molecular and supra-
molecular structure. Three-component reactions of this
general type can also provide, as a by-product, the twofold
intramolecular, and these doubtless control the overall
molecular conformation, in particular, the twist angles about
the C5ÐC57 and C51ÐC57 bonds (Table 1). The short OÁ Á ÁO
distance in the intramolecular OÐHÁ Á ÁO hydrogen bond is
consistent with the development of a signi®cant negative
charge on atom O6 [cf. form (Ia)]. Each of the intramolecular
hydrogen bonds gives rise to an independent S(8) motif
0
symmetrical compound 2,2 -methylenebis(5,5-dimethyl-3-
hydroxy-2-cyclohexen-1-one), (II), whose structure we have
reported recently (Low et al., 2003).
Within the heterocyclic ring of (I), the C4ÐC5 and C5ÐC6
distances (Table 1) are similar, and they cannot be associated
readily with double and single bonds, respectively. In addition,
the C4ÐN4 distance is very much shorter than the mean value
(Bernstein et al., 1995). The molecules are linked into chains
by a single intermolecular NÐHÁ Á ÁO hydrogen bond; amine
atom N4 in the molecule at (x, y, z) acts as a hydrogen-bond
donor, via atom H4B, to amide atom O6 in the molecule at
³ Postal address: Department of Electrical Engineering and Physics,
University of Dundee, Dundee DD1 4HN, Scotland.
Acta Cryst. (2004). C60, o191±o193
DOI: 10.1107/S0108270104001118
# 2004 International Union of Crystallography o191
Low, John N.
