Vinylogues and heterocyclic analogues of benzylidenemalonaldehydes

Abstract

Nine analogues of benzylidenemalonaldehyde (IV) were prepared by condensation of bis(dimethylamino)trimethinium perchlorate with two vinylogues of benzaldehyde and a series of heterocyclic aldehydes. The reaction intermediate was isolated and shown by 1H NMR spectroscopy to be the bis-iminium salt III. The conformation of 3-phenylprop-2-enylidenemalonaldehyde (IVa), determined by its 1H NMR spectrum, may serve as a more general model of arylmethylenemalonaldehydes.