A concise, efficient and versatile synthesis of amino-substituted benzo[b]pyrimido[5,4-f]azepines: synthesis and spectroscopic characterization, together with the molecular and supramolecular structures of three products and one intermediate.

A concise, efficient and versatile synthesis of amino-substituted benzo[b]pyrimido[5,4-f]azepines is described: starting from a 5-allyl-4,6-dichloropyrimidine, the synthesis involves base-catalysed aminolysis followed by intramolecular Friedel-Crafts cyclization. Four new amino-substituted benzo[b]pyrimido[5,4-f]azepines are reported, and all the products and reaction intermediates have been fully characterized by IR, H and C NMR spectroscopy and mass spectrometry, and the molecular and supramolecular structures of three products and one intermediate have been determined. In each of N,2,6,11-tetramethyl-N-phenyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepin-4-amine, CHN, (III), 4-(1H-benzo[d]imidazol-1-yl)-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, which crystallizes as a 0.374-hydrate, CHN·0.374HO, (VIIIa), and 6,7,9,11-tetramethyl-4-(5-methyl-1H-benzo[d]imidazol-1-yl)-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, CHN, (VIIIc), the azepine ring adopts a boat conformation, but with a different configuration at the stereogenic centre in (VIIIc), as compared with (III) and (VIIIa). In the intermediate 5-allyl-6-(1H-benzo[d]imidazol-1-yl)-N-methyl-N-(4-methylphenyl)pyrimidin-4-amine, CNN, (VIIb), the immediate precursor of 4-(1H-benzo[d]imidazol-1-yl)-6,8,11-trimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine, (VIIIb), the allyl group is disordered over two sets of atomic sites having occupancies of 0.688 (5) and 0.312 (5). The molecules of (III) are linked into chains by a C-H...π(pyrimidine) hydrogen bond, and those of (VIIb) are linked into complex sheets by three hydrogen bonds, one of the C-H...N type and two of C-H...π(arene) type. The molecules of the organic component in (VIIIa) are linked into a chain of rings by two C-H...π(arene) hydrogen bonds, and these chains are linked into sheets by the water components; a single weak C-H...N hydrogen bond links molecules of (VIIIc) into centrosymmetric R(10) dimers. Comparisons are made with some related compounds.