KINETIC STUDY OF A HOM0DIENYL-[1,5]-HYDROGEN SHIFT IN A VINYLZAZIRIDINE

摘要

The thermal rearrangement of an N-substituted vinylaziridine to the corresponding (Z)-allylic imine, i.e. a homodienyl-[1,5]-hydrogen shift, was studied at different temperatures in the range 40-90℃. ~1H NMR spectroscopy was used to follow the reaction. Rate constants and activation parameters were determined in solvents that differ in polarity, namely 1,4-dimethylbenzene, 1,2-dichlorobenzene and dimethylformamide (DMF). The activation enthalpies and entropies obtained clearly indicate that the solvent polarity has little influence on the rearrangement, since these values are almost the same in the three solvents used. The low ΔW~≠ values (89, 84 and 91 kJmol~(-1), respectively) are consistent with a concerted mechanism, while the activation entropies are all small and negative, which is also supportive of a cyclic transition state. The rate constant is slightly higher in the most polar of the solvents used, DMF.