Hydrolysis of cyclic unsymmetrical anti imidate salts. New evidence for stereoelectronic control

Abstract
The synthesis and the hydrolytic behavior of the cyclic imidate salts 7, 8, and 9 is reported. Under acidic conditions, the salt 7 gives the ester ammonium salt 21 and the salt 9 gives a 1:1 mixture of the ester ammonium salt 22 and the amide alcohol 23 as the rotamer 23B only. Under basic conditions, the salt 7 (or 8) gives a 2:8 (or 1:9) mixture of the amide alcohol rotamers 25A and 25B (or 27A and 27B) under kinetically controlled conditions. The salt 9 gives, as the kinetic product, the amide alcohol rotamer 23B only. These results can be rationalized on the basis of the stereoelectronic theory for the cleavage of tetrahedral intermediates and by taking into account that the nitrogen in tetrahedral intermediates must be either protonated under acidic conditions, or hydrogen bonded with the solvent under basic conditions, in order to observe the cleavage of a C—N bond.