Theoretical calculations of minimum energy structures and thermodynamics for the formation of cyclic amidines and imidates by intramolecular nucleophilic addition/elimination reactions

摘要

Theoretical calculations of minimum energy structures and thermodynamic terms using SCF theory with thermodynamic and solvation corrections have been made of the cyclisation of 1-amino-8-(acetylamino)naphthalene to give 2-methylperimidine with the liberation of water and of the related reaction of 1-hydroxy-8-(acetylamino)naphthalene to 2-methylnaphtho[1,8-d,e][1,3]oxazine. The calculations predict that in the gas phase the former reaction is strongly thermodynamically favourable (Delta G = -37.9 kJ mol(-1), Delta H = -0.6 kJ mol(-1) and T Delta S = +37.3 kJ mol(-1) at 298.2 K) whereas the latter is much less favourable (Delta G = -2.0 kJ mol(-1), Delta H = +31.1 kJ mol(-1) and T Delta S = +33.1 kJ mol(-1) at 298.2 K), The results are in qualitative agreement with experimental observations for the reactions in solution, Reasons for the different behaviour of the two reactions are discussed. [References: 12]