A series of (E)‐5‐(arylideneamino)‐1‐tert‐butyl‐1H‐pyrrole‐3‐carbonitriles and their reduction products to secondary amines: syntheses and X‐ray structural studies. Issue 1 (20th December 2017)

• Record Type: Journal Article
• Authors: Macías, Mario A.; Castillo, Juan-Carlos; Portilla, Jaime
• Is Part Of: Acta crystallographica. Volume 74:Issue 1(2018)
• Page Start: 82
• Page End: 93
• Publication Date: 2017-12-20
• Subjects: chemical reactions and mechanisms -- crystal structure -- N‐(pyrrol‐2‐yl)imines -- secondary amines -- Hirshfeld surface maps -- microwave‐assisted reaction -- reaction optimization; Crystallography -- Periodicals; Crystals -- Periodicals; 548.3
• DOI: 10.1107/S2053229617017260
• Languages: English
• ISSNs: 2053-2296

Abstract

Abstract : The synthesis and crystal structures of a series of ( E )‐5‐(arylideneamino)‐1‐ tert ‐butyl‐1 H ‐pyrrole‐3‐carbonitriles and their respective reduced products are presented. Interestingly, C—H…Cl interactions seem to help in the construction of the supramolecular structure of the precursors, while in the corresponding reduced compounds, these interactions appear less important compared with the observed (N, C)—H…N hydrogen bonds. Abstract : An efficent access to a series of N ‐(pyrrol‐2‐yl)amines, namely ( E )‐1‐ tert ‐butyl‐5‐[(4‐chlorobenzylidene)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C16 H16 ClN3, (7 a ), ( E )‐1‐ tert ‐butyl‐5‐[(2, 4‐dichlorobenzylidene)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C16 H15 Cl2 N3, (7 b ), ( E )‐1‐ tert ‐butyl‐5‐[(pyridin‐4‐ylmethylene)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C15 H16 N4, (7 c ), 1‐ tert ‐butyl‐5‐[(4‐chlorobenzyl)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C16 H18 ClN3, (8 a ), and 1‐ tert ‐butyl‐5‐[(2, 4‐dichlorobenzyl)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C16 H17 Cl2 N3, (8 b ), by a two‐step synthesis sequence (solvent‐free condensation and reduction) starting from 5‐amino‐1‐ tert ‐butyl‐1 H ‐pyrrole‐3‐carbonitrile is described. The syntheses proceed via isolated N ‐(pyrrol‐2‐yl)imines, which are also key synthetic intermediates of other valuable compounds. The crystal structures of the reduced compounds showed a reduction in the symmetry compared with the corresponding precursors, viz. Pbcm to P from compound (7 a ) to (8 a ) and P 21 / c to P from compound (7 b ) to (8 b ), probably due to a severe change in the molecular conformations, resulting in the loss of planarity observed in the nonreduced compounds. In all of the crystals, the supramolecular assembly is controlled mainly by strong (N, C)—H…N hydrogen bonds. However, in the case of (7 a )–(7 c ), C—H…Cl interactions are strong enough to help in the three‐dimensional architecture, as observed in Hirshfeld surface maps.