Unequivocal NMR assignments of the (E,Z) isomeric pairs 3 and 8 are possible by (Z,E) equilibration. Deprotonation of 2-methyl-l-phenylpropene (1) with n-BuLi under any conditions gives only a single allyl-metal derivative 2. Methylation of the latter gives the isomer (2)-3, while deuteriolysis leads to the isotopically labelled derivative 6 of the olefin 1; this proves the NMR assignments for 1 as well as the endo configuration of 2. The phenyl group gives rise to a differential shielding effect on the y-carbon nuclei in methyl and rnethylene groups along a CC double bond (ca. 7 ppm), and this effect is comparable to that along a CN double bond as in 8. The nitrile function in 5c is much less effective.

E/Z) Equilibria. Part 16. Lone Electron Pair Donor Quality of the Imino Function: Synthesis and Reactivity of Sterically Strongly Congested Iminocyclopentanes.-Sterically strongly hindered Schiff bases are constructed in order to develop suitable isoelectronic and isosteric model substances for the non-observable carbanions of vinyllithium compounds. (V) is obtained by permethylation; it forms salts such as (VI) by N-protonation. The C= N double bond is strongly shielded against nucleophilic attack and cannot be hydrolyzed. Nitration (and bromination) occur in the aromatic ring showing strongly the directing power of the lone pair of the imino function. This π-donor quality is assessed by probing weaker electrophiles and qualitative competition experiments. -(KNORR, R.; HINTERMEYER-HILPERT, M.; MEHLSTAEUBL, J.; HOANG THI PHUNG; NEUNER, B.; BOEHRER, P.; Chem.

Deprotonation of (I) leads to the endo‐configurated allyl anion (II) exclusively.

Sterically Congested Molecules. Part 6. Lone Electron Pair Donor Quality of the Imino Function: Increased Front Strain and Electronic Substituent Effects on Sterically Accelerated Nitrogen Inversion in Iminocyclopentanes.-The p-substituents in (I) are modified without interfering reactions at the C=N double bond. For a quantification of the lone-pair donor quality of the imino function in the substituted series (Ib) and (Ic) ( total 13 examples) their activation parameters of stereomutation ( Hammett values) are invesigated. -(KNORR, R.; HOANG THI PHUNG; MEHLSTAEUBL, J.; HINTERMEYER-HILPERT, M.; LUEDEMANN, H.-D.; LANG, E.; SEXTL, G.; RATTAY, W.; BOEHRER, P.; Chem. Ber. 126 (1993) 1, 217-224; Inst. Org. Chem., Univ.