Hydrogen-bonded ribbons in ethyl (E)-3-[2-amino-4,6-bis(dimethylamino)pyrimidin-5-yl]-2-cyanoacrylate and 2-[(2-amino-4,6-di-1-piperidyl-pyrimidin-5-yl)methylene]malono-nitrile

The pyrimidine rings in ethyl (E)-3-[2-amino-4,6-bis(dimethylamino)pyrimidin-5-yl]-2-cyanoacrylate, C14H20N6O2, (I), and 2-[(2-amino-4,6-di-1-piperidylpyrimidin-5-yl)methylene] malononitrile, C18H23N7, (II), which crystallizes with Z' = 2 in the P (1) over bar space group, are both nonplanar with boat conformations. The molecules of ( I) are linked by a combination of N - H center dot center dot center dot N and N - H center dot center dot center dot O hydrogen bonds into chains of edge-fused R-2(2)(8) and R-4(4)(20) rings, while the two independent molecules in (II) are linked by four N - H center dot center dot center dot N hydrogen bonds into chains of edge-fused R-2(2)(8) and R-2(2)(20) rings. This study illustrates both the readiness with which highly-substituted pyrimidine rings can be distorted from planarity and the significant differences between the supramolecular aggregation in two rather similar compounds.