Chemistry of amidines. Part 4. Analysis of conformation for a series of N′-pyridylformamidines by 1H NMR spectroscopic, molecular mechanical and semi-empirical molecular orbital methods

Abstract

The results of NOE measurements for a series of N′-pyridylformamidines and their conjugate acids have been interpreted with the aid of molecular mechanical and semi-empirical molecular orbital calculations. Conformations about the pyridyl–N_im and the C_f–N_am bonds are determined by delocalisation of the N_am lone pair, dipolar interactions, steric interactions and, in the conjugate acids, long range interaction between the pyridyl N and the electron-deficient formyl H.