X-ray mapping in heterocyclic design: IX. X-ray structure investigation of conjugated aminodienes

The single-crystal structures of two aminodienes containing an oxazole fragment, namely, 1-piperidyl-4-[5-(4-nitrophenyl)-oxazol-2-yl]-buta-1,3-diene C18H19N3O3 (IIa) and 1-hexamethyleneimine-4-[5-(4-nitrophenyl)-oxazol-2-yl]-buta-1,3-diene C19H21N3O3 (IIb), are studied by X-ray diffraction. Structures Ha [a = 16.181(6) Angstrom, b = 5.939(3) Angstrom, c = 17.337(9) Angstrom, beta = 96.13(2)degrees, Z = 4, and space group P2(1)] and IIb [a = 7.4704(11) Angstrom, b = 10.9904(19) Angstrom, c = 43.434(6) Angstrom, beta = 91.24(1)degrees, Z = 8, and space group P2(1)/c] are solved by the direct method and refined to R = 0.060 and 0.238, respectively. Although the ring sizes of the cyclic amines in compounds IIa and IIb are different, the designs of two structures are identical. Each structure contains two topologically identical but crystallographically independent molecules. In structure IIa, the intramolecular hydrogen bonds between the N atoms of the oxazole fragments and the H atoms of the diene fragments are formed. In structure IIb, similar bonds are absent. (C) 2002 MAIK "Nauka/Interperiodica".