✍ Scribed by Anita Hussénius; Peter Somfai; David Tanner
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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 "C. 'H NMR spectroscopy was used to follow the reaction. Rate constants and activation parameters were determined in solvents that differ in polarity, namely l,4-dimethylbenzene, 1,Z-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 AH * values (89, 84 and 91 kJmol-', 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.
📜 SIMILAR VOLUMES
The kin&a OC a hydrogen stift reaction was investigated. The proce~ is governed by large tunnel contributions and takes place during the rcarrangcmcnt of a light-gcncratcd. transient hexahydrocarbazole into a srable hcxahydr~bazole. Luge Isotope effects were observed when the migz~tirg hydrogen was