24099-52-3Relevant articles and documents
Ene-diamine versus imine-amine isomeric preferences
Reich, B. Jesse E.,Greenwald, Erin E.,Justice, Aaron K.,Beckstead, Brittany T.,Reibenspies, Joseph H.,North, Simon W.,Miller, Stephen A.
, p. 8409 - 8416 (2005)
Cyanide-catalyzed aldimine coupling was employed to synthesize compounds with 1,2-ene-diamine and α-imine-amine structural motifs: 1,2,N,N′-tetraphenyletheylene-1,2-diamine (13) and (±)-2,3-di-(2- hydroxyphenyl)-1,2-dihydroquinoxaline (17), respectively. Single-crystal X-ray diffraction provided solid-state structures and density functional theory calculations were used to probe isomeric preferences within this and the related hydroxy-ketone/ene-diol system. The ene-diamine and imine-amine core structures were calculated (B3LYP/6-311++G(d,p)) to be essentially identical in energy (ΔG = 0.2 kcal/mol in favor of the imine-amine, within the error of the calculation). However, additional effects-such as π conjugation-in 13 render an ene-diamine structure that is slightly more stable than the imine-amine tautomer (14) (ΔG = 0.2-0.7 kcal/mol, within the error of the calculation). In contrast, the intramolecular hydrogen bonding present in 17 significantly favors the imine-amine isomer over the ene-diamine tautomer (18) (ΔG = 7.2-8.9 kcal/mol). For both 13 and 17, the optimized calculated structures (B3LYP/6-31+G(d′)) are identical to those observed by single-crystal X-ray diffraction.
