Synthesis and properties of N-cyanodimethyltetradehydro-trideca-, -pentadeca-, -heptadeca-, and -nonadeca-azafulvenes, and benzannelated N-cyanotridecaazafulvene derivatives

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Syntheses of N-cyano-5,10-dimethylcyclotrideca-2,4,10,12-tetraene-6,8-diynyfidenamine, N-cyano 5,10-di-tert-butylcyclotrideca-2,4,10,12-tetraene-6,8-diynyfidenamine, N-cyano-7,12- dimethylcyclopentadeca-2,4,6,12,14-pentaene-8,10-diynylidenamine, N-cyano-7,12-dimethylcycloheptadeca-2,4,6,12,14,16-hexaene-8,10-diynylidenamine, and N-cyano-9,14-dimethylcyclononadeca-2,4,6,8,14,16,18-heptaene-10,12-diynylidenamine are described. Examination of the 1H NMR spectra indicates that the cyclo-C13 and cyclo-C17 compounds are paratropic, while the C15 and C19 compounds are diatropic. Syntheses of benzannelated derivatives of the first mentioned annulene, i.e. N-cyano-11-methyl-12,13,14,15-tetradehydro-7H-benzocyclotridecen-7-ylidenamine and N-cyano-5,6,7,8-tetra - dehydro-15H-dibenzo[a,g]cyclotridecen-15-ylidenamine, are also described. Dynamic NMR analysis of the ring protons suggested a syn–anti isomerization of the cyano group at the exocyclic position of the macrocycle. The influence of the cyanoimino group and benzannelation upon the tropicity of the tetradehydro[13]annulenes is discussed on the basis of their 1H NMR and electronic spectra.