Synthesis and Conformational Analysis of N-Azulenyl-N-methyl Amides: Influence of Coplanarity on Amide Conformational Preference

Abstract

We synthesized a series of N-azulenyl-N-methylamides and investigated their conformational preferences in solution and in the solid state. N-(1-Azulenyl)-N-methyl amides 12 and N-(6-azulenyl)-N-methyl amides 14 adopt the cis form almost exclusively in solution and in the crystal state, like general N-methyl aromatic amides such as N-methylbenzanilide and N-methylacetanilide. However, N-(2-azulenyl)-N-methyl amides 13 exhibit high ratios of the trans form in solution and adopt the trans form in the solid state due to the high degree of coplanarity of the 2-azulenyl moiety and the amide plane.