Abstract
AbstractThe synthesis of tripodal carboxamide ligands using one‐pot phosphite coupling reactions with nitrilotriacetic acid (NTA) and 4‐substituted anilines is well established. Generation of such tripodal ligands using ortho‐substituted anilines (2,6−RArNH2, R=F, Me, iPr) has proven to be challenging. The reaction between NTA and 2,6−RArNH2 using triphenylphosphite as a coupling reagent did not yield the desired tripodal carboxamide. Rather, the formation of 3,5‐dioxo‐1‐piperazine intramolecular coupling products N‐(2,6‐difluorophenyl)‐3,5‐dioxo‐1‐piperazine‐N‐(2,6‐difluorophenyl)acetamide (1), N‐(2,6‐dimethyphenyl)‐3,5‐dioxo‐1‐piperazine‐N‐(2,6‐dimethylphenyl)acetamide (2) and N‐(2,6‐diisopropylphenyl)‐3,5‐dioxo‐1‐piperazine‐N‐(2,6‐diisopropylphenyl)acetamide (3) was observed. All three compounds have been extensively characterized using nuclear magnetic resonance, Fourier‐transform infra‐red and mass spectrometry. X‐ray diffraction analysis yielded solid state structures of 2 and 3. Substituents at the ortho position of aniline thus favours intramolecular cyclization over the formation of tripodal carboxamide ligands, preventing preparation of the desired bulky ligand.
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call