77390-49-9Relevant academic research and scientific papers
13 C shieldings in syn and anti aldimines and ketimines
Fraser, Robert R.,Banville, Jacques,Akiyama, Fuminori,Chuaqui-Offermanns, Noemi
, p. 705 - 709 (2007/10/02)
The 13 C chemical shifts in a variety of aldimines and in both acyclic and cyclic ketimines have been examined.A comparison of the shieldings at the α carbons in syn versus anti stereoisomers shows a consistent upfield shift of 8-11 ppm in the syn isomer.The greater magnitude found in imines vs. oximes or hydrazones is a clear indication of a steric origin for the differential shieldings.The shifts in the imines of cyclohexanones exhibited stereochemically dependent effects of methyl substitution, very similar to those in analogous oxime and hydrazone derivatives.Chemical shift differences in the syn isomers of the α-phenetylimines of chiral aldimines and ketimines allow a facile measurement of diastereomer ratios for such compounds.
Empirical Substituent Parameters for E/Z Equilibrium Constants
Knorr, Rudolf
, p. 2441 - 2461 (2007/10/02)
A set of substituent parameters λd is proposed which permits the prediction of E/Z equilibrium constants for olefins, enamines, Schiff bases, hydrazones, semicarbazones, oximes, and nitrones.The set includes values for the "non-bonded" electron pairs and the nitrone oxygen as well as for amino or phenyl groups coplanar and orthogonal to the double bond.Ketone anils prefer a perpendicular phenyl group.Principal limitations of the very simple heuristic model are discussed.The model is also applied to the "cis"- and "ortho"-effects, enolates, and Schiff bases of cyclic and bicyclic ketones.
