No 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 ,I -dicyano-2,2-bis(dimethy1amino)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.Vinylogous activation of the methyl group by cyano substituents is much stronger than by ester substituents.' Thus, et hylidenemalononitrile I condenses with N,N-dimethyldichloromethyleneaminium chloride 22 to the new 2-chloro dienamine 3 whereas the diester analogue fails to react.' The substitution of the chlorine atom in 3 with N,N-dimethylamine leads to the twofold push-pull butadiene 43 (Scheme 1). Compound 4 is the vinylogue4 of the known I,l-dicyano-2,2bis(dimethy1amino)ethylene 5 (Scheme 2).

Phosgeniminium salt 1 easily condenses with vinylogues of malononitrile to yield new y,yrdicyano-a-chlorodienamines Lz which can undergo substitutions and heterocyclisation reactions.Viny1ogues of malonate do not react with 1 whereas those of cyanoacetate 21 lead to the formation of new a-pyrones 2.

Exceptionally Short Central Bonds in the Cumulogue and the Vinylogue of 2,2-Dicyano-1,1-bis(dimethylamino)ethylene.-The X-ray structures of the twofold push-pull butatriene dinitriles (V) and (IX) are determined (both: P21/c, Z = 4). The compounds possess a highly dipolar character because of an important resonance contribution. These compounds may be compared with the known title ethylene. The exceptionally short central bonds in (V) and (IX) support the concept of vinylogous and cumulogous polar conjunction. -(TINANT, B.; DECLERCQ, J.-P.; BOUVY, D.; JANOUSEK, Z.; VIEHE, H. G.; J. Chem. Soc., Perkin Trans. II (1993) 5, 911-915; Lab. Chim. Phys. Cristallogr., Univ. Cathol. Louvain, 1348 Louvain-la-Neuve, Belg.; EN)

1993nitriles nitriles (acyclic compounds) P 0350 -126Condensation of Dichloromethyleniminium Chloride with Alkylidenemalononitriles or Alkylidenecyanoacetates.-Condensation of the title compound (II) with malonodinitriles, e.g. (I) , easily yields the new compounds (III), which are stable in neutral aqueous solution, due to their stabilizing push-pull conjugation. They undergo chlorine substitution by various nucleophilic reagents, e.g. to (V) with inversion of configuration, and heterocyclization reactions, e.g. to (VI) and, with loss of malononitrile, to (VIII) and (IX). Condensation of (II) with alkylidenecyanoacetates (X) is also accomplished, yielding new pyrones of type (XII) by immediate cyclization of the intermediates (XI), while condensation with the corresponding malonodiesters does not take place under these conditions. -(BOUVY, D.; JANOUSEK, Z.; VIEHE, H. G.; Bull.