Dynamic 1 H NMR study of rotational energy barrier around the aryl-nitrogen single bond in γ-spiroiminolactones derived from reaction between 2,6-dimethylphenyl isocyanide and dialkyl acetylenedicarboxylates in the presence of phendione

摘要: The Dynamic effects arc observed in 1 H NMR spectra of highly functional γ-spiroiminolactones such as dimethyl-5-(2,6-dimelhylphenylimino)-6'-oxo-5H,6H-spiro[furan-2,5'- [1,10]phenanthroline]-3,4-dicarboxylate and di-tert-butyl-5-(2.6-dimethylphenylimino)-6'-oxo-5H, 6H-spiro[furan-2, 5'-[1,10]phenanthroline]-3,4-dicarboxylate. calculated free-energy activation (∇G ≠ ) for restricted rotation around the aryl-nitrogen single bonds 4a 4b amounts to (44.4 45.3)±2 kj.mo -1 with first order rate constant (k=109.9 111.0 s at appropriate temperature respectively.