title: Five closely related 4-chloro-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepines: similar molecular structures but different supramolecular assemblies.
abstract: Dibenz[b,f]azepine (DBA) is a privileged 6-7-6 tricyclic ring system of importance in both organic and medicinal chemistry. Benzo[b]pyrimido[5,4-f]azepines (BPAs), which also contain a privileged 6-7-6 ring system, are less well investigated, probably because of a lack of straightforward and versatile methods for their synthesis. A simple and versatile synthetic approach to BPAs based on intramolecular Friedel-Crafts alkylation has been developed. A group of closely-related benzo[b]pyrimido[5,4-f]azepine derivatives, namely (6RS)-4-chloro-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, C14H14ClN3, (I), (6RS)-4-chloro-8-hydroxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, C14H14ClN3O, (II), (6RS)-4-chloro-8-methoxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, C15H16ClN3O, (III), and (6RS)-4-chloro-8-methoxy-6,11-dimethyl-2-phenyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, C21H20ClN3O, (IV), has been prepared and their structures compared with the recently published structure [Acosta-Quintero et al. (2015). Eur. J. Org. Chem. pp. 5360-5369] of (6RS)-4-chloro-2,6,8,11-tetramethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, (V). All five compounds crystallize as racemic mixtures and they have very similar molecular conformations, with the azepine ring adopting a boat-type conformation in each case, although the orientation of the methoxy substituent in each of (III) and (IV) is different. The supramolecular assemblies in (II) and (IV) depend upon hydrogen bonds of the O-H...N and C-H...π(arene) types, respectively, those in (I) and (V) depend upon π-π stacking interactions involving pairs of pyrimidine rings, and that in (III) depends upon a π-π stacking interaction involving pairs of phenyl rings. Short C-Cl...π(pyrimidine) contacts are present in (I), (II) and (IV) but not in (III) or (V).
authors.affiliation: Laboratorio de Síntesis Orgánico, Escuela de Química, Universidad Industrial de Santander, AA 678 Bucaaramanga, Colombia.
authors.forename: Lina M
authors.initials: LM
authors.lastname: Acosta
authors.affiliation: Laboratorio de Síntesis Orgánico, Escuela de Química, Universidad Industrial de Santander, AA 678 Bucaaramanga, Colombia.
authors.forename: Jorge
authors.initials: J
authors.lastname: Jurado
authors.affiliation: Laboratorio de Síntesis Orgánico, Escuela de Química, Universidad Industrial de Santander, AA 678 Bucaaramanga, Colombia.
authors.forename: Alirio
authors.initials: A
authors.lastname: Palma
authors.affiliation: Departamento de Química Inorgánica y Orgánica, Universidad de Jaén, 23071 Jaén, Spain.
authors.forename: Justo
authors.initials: J
authors.lastname: Cobo
authors.affiliation: School of Chemistry, University of St Andrews, Fife KY16 9ST, Scotland.
authors.forename: Christopher
authors.initials: C
authors.lastname: Glidewell
keywords: BPAs; azepines; benzo[b]pyrimido[5,4-f]azepines; crystal structure; hydrogen bonding; molecular conformation; novel synthesis; π-stacking interactions