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, 1H and 13C 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, C22H24N5, (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, C21H19N5·0.374H2O, (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, C24H25N5, (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, C22N21N5, (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...?(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...(arene) type. The mol­ecules of the organic component in (VIIIa) are linked into a chain of rings by two C-H...-(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 R22(10) dimers. Comparisons are made with some related compounds.