Abstract
The known preparative route to macrocycles from aromatic diamines and di-iminoisoindoline has been extended to the use of starting materials containing bulky alkyl substituents. A number of metal-free macrocycles and metal derivatives have been isolated, together with some simpler condensation products. These materials are considerably more soluble than the compounds which did not contain bulky alkyl substituents and p. m. r. studies have readily been carried out. From these spectra, it is clearly demonstrated that nickel derivatives of the pyridine macrocycle do not contain extensive cyclically delocalized pi-electron systems as an X-ray crystallographic study had suggested, but that they are cross-conjugated. It is also shown in the case of some dicondensation products, that syn- and anti-geometrical isomers are possible and the relative concentration of each in solution at 34° has been calculated from the p. m. r. spectra. Difficulties which were encountered in macrocyclic syntheses are explained in part on the basis of solubilities and of electronic effects of the alkyl substituents. The preparation of some 2,4-disubstituted pyrimidine derivatives is outlined and their reactions with phthalonitrile and di-iminoisoindolines described. It was not found possible to obtain isolable macrocyclic products here but evidence is available for their presence in some reaction mixtures.