Exceptionally short central bonds in the cumulogue and the vinylogue of 2,2-dicyano-1,1-bis(dimethylamino)ethylene

Abstract

The preparation and crystal structures of twofold push-pull butatriene 2-cyano-5,5-bis(dimethylamino)penta-2,3,4-trienentrile 9 and butadiene 2-cyano-5,5-bis(dimethylamino)penta-2,4-dienenitrile 4 with bis-dimethylamino and dicyano substituents are described. These compounds may be compared with the known corresponding ethylene derivative 1,1-dicyano-2,2-bis(dimethylamino)ethylene 5. The exceptionally short central bonds in 9 and 4 are in agreement with the earlier proposed concept of cumulogy and of vinylogy to 5.