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A series of ( E )‐5‐(arylideneamino)‐1‐ tert ‐butyl‐1 H ‐pyrrole‐3‐carbonitriles and their reduction products to secondary amines: syntheses and X‐ray structural studies
Author(s) -
Macías Mario A.,
Castillo Juan-Carlos,
Portilla Jaime
Publication year - 2018
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229617017260
Subject(s) - series (stratigraphy) , pyrrole , reduction (mathematics) , chemistry , medicinal chemistry , stereochemistry , mathematics , organic chemistry , geometry , paleontology , biology
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, C 16 H 16 ClN 3 , (7 a ), ( E )‐1‐ tert ‐butyl‐5‐[(2,4‐dichlorobenzylidene)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C 16 H 15 Cl 2 N 3 , (7 b ), ( E )‐1‐ tert ‐butyl‐5‐[(pyridin‐4‐ylmethylene)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C 15 H 16 N 4 , (7 c ), 1‐ tert ‐butyl‐5‐[(4‐chlorobenzyl)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C 16 H 18 ClN 3 , (8 a ), and 1‐ tert ‐butyl‐5‐[(2,4‐dichlorobenzyl)amino]‐1 H ‐pyrrole‐3‐carbonitrile, C 16 H 17 Cl 2 N 3 , (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 2 1 / 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.