Conformational analysis of N→BH₃, N→BF₃, and N-CH₃⁺complexes with ibuprofen-derivative amides

Abstract

The synthesis and structural characterization of novel amine-borane adducts of ibuprofen derivatives are presented. The changes of the electron density on the carbonyl and pyridine ring after formation of N→BH 3 , N→BF 3 , and N-CH 3 + have been confirmed by 1 H, 11 B, 13 C, and 19 F NMR, further supported by homonuclear and heteronuclear correlations. Moreover, electrostatic interactions -H + ··· − F and the nonclassical H + ··· − H-were identified by NMR spectra. The analysis of the resulting molecular structures offered insights on the 2-aminopyridine N→B adducts. The N→BH 3 adduct formed a single molecular arrangement, both in C 6 D 6 and CDCl 3 .The same behavior was observed for the N→BF 3 adduct in CDCl 3 . However, two conformers of this adduct were detected in C 6 D 6 . All adduct geometries were corroborated by density functional theory computational calculations.