Synthesis and Study of the Crystal Structure of 2-[(Dipyrrolidin-1-yl) methylene] malononitrile

This study aims to synthesis 2-[(dipyrrolidin-1-yl)methylene] malononitrile 2 and identify its crystal structure by X-ray diffraction analysis. 2-[(dipyrrolidin-1-yl)methylene] malononitrile was prepared by a direct displacement of the methylthio group (SMe) in the 2-[bis(methylthio)methylene] malononitrile 1 with pyrrolidine as cyclic secondary amine by conjugating addition-elimination reaction under reflux conditions for two hours. The compound was obtained in high yield (80%). The structure of compound 2-[(dipyrrolidin-1-yl)methylene] malononitrile2  was identified by performing X-ray diffraction analysis. Suitable crystals of compound 2 were grown by slow evaporation of methanol solution of the compound. The compound 2 crystallized in an orthorhombic crystal system with a space group of Pbcn. In the title compound, the two cyanide groups and the two pyrrolidine rings adopted trans configurations across the C2=C3 bond. The bond lengths and angles of the two pyrrolidinyl rings in the compound are within the normal range. The maximum deviation of N5/C2/C3/C4/N5a/C4a is 0.002(1) around C4, and no deviation has been recorded for the fragment N1/N1a/C2/C3 (0.000 (1)°). The dihedral angle between the pyrrolidine ring and N1/N1a/C2/C3 is 33.06(8)°, and the dihedral angle between the pyrrolidine ring and N5/C2/C3/C4/N5a/C4a is 50.57(7)°. The crystal packing is stabilized by two intermolecular and one intramolecular C---H…N hydrogen bonds, which form a one-dimensional polymeric chain along the axis.