(9E)-9-Benzylidene-3-methyl-2-methyl- sulfanyl-5-phenyl-5,6,7,8,9,10-hexa- hydropyrimido[4,5-b]quinolin-4(3H)- one: polarized molecules within hydrogen-bonded bilayers Diana Becerra, a Braulio Insuasty, a Justo Cobo b and Christopher Glidewell c * a Departamento de Quı ´mica, Universidad de Valle, AA 25360 Cali, Colombia, b Departamento de Quı ´mica Inorga ´nica y Orga ´nica, Universidad de Jae ´n, 23071 Jae ´n, Spain, and c School of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland Correspondence e-mail: cg@st-andrews.ac.uk Received 10 June 2010 Accepted 15 June 2010 Online 7 July 2010 The molecules of the title compound, C 26 H 25 N 3 OS, which was prepared by means of an acid-catalysed cyclocondensation reaction between a 6-aminopyrimidinone and 2,6-dibenzyl- idenecyclohexanone, exhibit a polarized electronic structure, namely (9E)-9-benzylidene-3-methyl-2-methylsulfanyl-5-phenyl- 3,5,6,7,8,9-hexahydropyrimido[4,5-b]quinolin-10-ium-4-olate, involving charge separation in the vinylogous amide portion. Four hydrogen bonds, two each of the C—HO and C— H(arene) types, link the molecules into bilayers comprising inversion-related pairs of sheets, each containing a single type of R 4 3 (36) ring. Comment In our search for new bioactive compounds based on heterocyclic frameworks, pyrimido[4,5-b]quinolines have emerged as interesting targets because of their structural analogy with flavones. We report here the molecular and supramolecular structure of the title compound, (I), which was prepared using an acid-catalysed cyclocondensation between (2E,6E)-2,6-dibenzylidenecyclohexanone and 6-amino-3- methyl-2-(methylsulfanyl)pyrimidin-4(3H)-one (see scheme). This synthetic procedure may be contrasted with the synthesis of the related compound, (II), which employed a multi- component cyclocondensation reaction under environmen- tally friendly solvent-free conditions, mediated by microwave radiation (Low, Cobo, Cisneros et al. , 2004). The molecules of (I) contain a stereogenic centre at C5 (Fig. 1) and the reference molecule was selected as one having the R configuration at C5. However, the centrosymmetric space group accommodates equal numbers of the two enantiomorphs. In addition, the two rings which are fused at the C5a—C9a bond (Fig. 1) are both nonplanar. The hetero- cyclic ring containing atom N10 adopts a boat-type confor- mation, with atoms C5 and N10 acting as the stem and stern of the boat, respectively. The ring-puckering parameters (Cremer & Pople, 1975) for the atom sequence N10/C9a/C5a/ C5/C4a/C10a are Q = 0.205 (2) A ˚ , = 103.8 (6) and ’ = 2.6 (7) , whereas the ideal puckering angles for a boat conformation are = 90 and ’ = 60k , where k represents an integer. The adjacent carbocyclic ring adopts an envelope confor- mation, folded across the line C6C8, with ring-puckering parameters, for the atom sequence C5a—C6—C7—C8—C9— C9a, of Q = 0.481 (3) A ˚ , = 58.6 (4) and ’ = 117.6 (4) . The angles may be compared with the ideal values for an envelope conformation of = 54.7 and ’ = 60k , where k again represents an integer. By contrast, the pyrimidine component of the fused ring system is planar. The remainder of the molecular conformation can be specified in terms of just three torsion angles (Table 1), defining the orientation of the various substituents relative to the adjacent components of the fused ring system. While the C atom of the methylsulfanyl substi- organic compounds Acta Cryst. (2010). C66, o389–o391 doi:10.1107/S0108270110023139 # 2010 International Union of Crystallography o389 Acta Crystallographica Section C Crystal Structure Communications ISSN 0108-2701