Hydrogen bonding in 2-amino-4,6-dimethoxypyrimidine, 2-benzylamino-4,6-bis(benzyloxy)pyrimidine and 2-amino-4,6-bis(N-pyrrolidino)pyrimidine: chains of fused rings and a centrosymmetric dimer.

Molecules of 2-amino-4,6-dimethoxypyrimidine, C(6)H(9)N(3)O(2), (I), are linked by two N-H.N hydrogen bonds [H.N 2.23 and 2.50 A, N.N 3.106 (2) and 3.261 (2) A, and N-H.N 171 and 145 degrees ] into a chain of fused rings, where alternate rings are generated by centres of inversion and twofold rotation axes. Adjacent chains are linked by aromatic pi-pi-stacking interactions to form a three-dimensional framework. In 2-benzylamino-4,6-bis(benzyloxy)pyrimidine, C(25)H(23)N(3)O(2), (II), the molecules are linked into centrosymmetric R(2)(2)(8) dimers by paired N-H.N hydrogen bonds [H.N 2.13 A, N.N 2.997 (2) A and N-H.N 170 degrees ]. Molecules of 2-amino-4,6-bis(N-pyrrolidino)pyrimidine, C(12)H(19)N(5), (III), are linked by two N-H.N hydrogen bonds [H.N 2.34 and 2.38 A, N.N 3.186 (2) and 3.254 (2) A, and N-H.N 163 and 170 degrees ] into a chain of fused rings similar to that in (I).