¹³C NMR studies of cis–trans isomerization of N‐benzylidene‐propyl‐ and ‐substituted aryl‐amines induced by a lanthanide shift reagent

Abstract

The 13C chemical shifts of cis-and trans-benzylidenepropylamine and substituted benzylideneanilines were analysed after additons of Eu(fod),. The cisltrans ratio increases as the amount of lanthanide shift reagent increased. The cis isomers showed large lanthanide-induced shifts, whereas the trans isomers showed little or no effect.

β-Lactams fromD-Erythrose-Derived Imines: A Convenient Synthesis of 2,3-Diamino-2,3-dideoxy-D-mannonic-Acid Derivatives

“…This agrees well with literature data showing that (E)-and (Z)-aldimines equilibrate, resulting, as a rule, in (E)/(Z)-mixtures b 99 : 1 [67] [68] (for mixtures of ( E )-and ( Z )-aldimines, see, e.g., [69] [70]). The imines were usually treated directly with the ketene precursor.…”

“…Similarly, the d-manno-or d-allo-configured 28c results from a (Z)-imine [74], indicating that the (Z)-imine derived from 16 and 23 is more reactive than its (E)-isomer (cf. [67] [70]), or that it equilibrates more slowly than the imine 26. The imines derived from the cyclic aldehydes 6 and 17 led to single lactams possessing an opposite configuration at C(2) and C(3), indicating opposite directions of the conrotatory ring closure of the zwitterionic intermediates 24B and 17B (Fig.…”

Keto- Enol Tautomerism of 2-Hydroxy Naphthylideneaniline with Lanthanide Shift Reagent Pr(fod)3in Different Solvents

“…[6][7][8] Theoretical studies of tautomeric equilibrium in orhto-hydroxy schiff-bases have been reported. [9][10][11] Earlier [12][13][14] we have reported the cistrans isomerization of benzylideneaniline on addition of Eu(fod) 3 .…”