Kinetic vs Thermodynamic Selectivity

The formal complex of an imine RCH=NR with a zirconocene of C2v symmetry will be formed as a racemic mixture, with equal amounts of two enantiomers. If a zirconaaziridine possesses another stereogenic element, it will have two diastereomers of unequal energy, and they may be generated in a kinetic ratio that is not equal to their thermodynamic ratio. 

Similarly, a difference between the kinetic and thermodynamic selectivities was observed by Taguchi and coworkers while generating zirconaaziridines by 

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Fig.2. Free energy diagram showing kinetic vs. thermodynamic selectivity...

Dioxabicyclo[3.2.1]octane, the carbon skeleton of 1,6-anhydropyranose, is present in plant extracts and pheromones, and it is a crucial fragment in orally active 5-lipoxygenase inhibitors. The synthon 6,8-dioxabicyclo[3.2.1]octane-3-one (1102) is readily prepared from ( S)-malic acid-derived diol 45a, as shown in Scheme 162 [234]. Silylation of ketone 1099 with TBS triflate provides the kinetically derived silyl enol ether 1100 (10 1 kinetic vs. thermodynamic selectivity) in high yield. Lewis acid cyclization of the cyclic ortho ester 1100 affords the bicycloketone 1102 in 25.5% overall yield starting from (iS)-malic acid. 

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