Kinetics oxirane isomerization

The -deprotonation reaction was initially considered as the normal mode of oxirane isomerization in basic media with a-deprotonation appearing as an alternative pathway when the principal process was slowed. Recent studies based on kinetic studies, calculations and labeling experiments, along with advances in the determination of the organolithium... 

Based on this feature, aggregation states of transition-state structures for base-promoted isomerization of oxiranes have been established by kinetic studies of LDA-mediated isomerizations of selected oxiranes in nonpolar media in the presence of variable concentrations of coordinating solvents (ligands). Results reported provide the idealized rate law V = [ligand]" [base] [oxtrane] for a-deprotonation and v = fc[ligand]°[base] / [oxirane]... 

The growing interest in enantioselective isomerization of meso oxiranes to allylic alcohols arises from the ready availabihty of starting materials and the synthetic value of the homochiral products. First apphed to simple meso cycloalkene oxides, this methodology has been successfully exteuded to fuuctioualized meso oxiranes, and even to the kinetic resolution of racemic oxiranes, demonstrating its potential in accessing highly advanced synthons. 

In a recent theoretical study [MP2, B3LYP, CCSD(T)]112 the inversion at the oxygen of the (9-methylated oxirane cation 39 was calculated to be 15.7 kcal mol-1, which agrees well with the experimentally determined value for cation 38. Cation 39 is kinetically stable because a high-energy barrier (35.3 kcal mol-1) separates it from the ring-opened, significantly more stable isomeric oxonium ions (Scheme 4.5). In... 

Kinetic examinations have been made in order to shed light on the reaction mechanism. For oxiranes with asymmetrical structures isomerization takes place in both directions (Eq. 142). ... 

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