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Sterically Congested Molecules, 6. Lone Electron Pair Donor Quality of the Imino Function: Increased Front Strain and Electronic Substituent Effects on Sterically Accelerated Nitrogen Inversion in Iminocyclopentanes
Author(s) -
Knorr Rudolf,
Hoang Thi Phung,
Mehlstäubl Johann,
Hintermeyer;Hilpert Monika,
Lüdemann Hans;Dietrich,
Lang Elmar,
Sextl Gerhard,
Rattay Wilfried,
Bührer Petra
Publication year - 1993
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19931260130
Subject(s) - chemistry , steric effects , substituent , lone pair , double bond , electronic effect , stereochemistry , nitrogen inversion , molecule , reactivity (psychology) , medicinal chemistry , crystallography , nitrogen , organic chemistry , medicine , alternative medicine , pathology
The p ‐substituents of 2,6‐dimethyl‐ N ‐(2,2,5,5‐tetramethylcyclopentylidene)anilines are modified without interfering reactions at the CN double bond. The resultant series ( 5 – 8, 10 – 19 ) shows a strong (ca. —4.7 kcal/mol) steric acceleration of ( E / Z ) diastereotopomerization by front strain along the CN double bond but also the usual electronic substituent dependence, characterized by a Hammett s̀ p – correlation (Q = +2.7). Conversely, the substituent constant for lithium at the p ‐position of 7 may be estimated. The volume of activation is 1.5(8) cm 3 mol –1 for 5 . The π donor quality of the imino group corresponds to ca. 55 (±8)% of P π character as evaluated by spectral ( 13 C NMR of 5 and 13 , IR of 13 ) and reactivity data (of 13 ).