The synthesis of enantiomerically pure a-hydroxyaldehydes

Solladie later refined the reduction procedure, and applied the methodology to the synthesis of nonracemic epoxides [7]. Interestingly, he discovered that the addition of an equimolar amount of anhydrous zinc chloride to the ketone substrate in 

In the presence of a metal cation capable of chelation, transition state (8) was proposed to be favoured the high levels of diastereoselectivity observed in the ZnCyDIBAL reduction can therefore be rationalized on the basis of intermolecular hydride transfer from the least hindered face of the chelated, prochiral carbonyl system. 

It was originally proposed that in the absence of a chelating metal counterion, conformation (9) would be favoured owing to the electronic repulsion of the oxygen atoms [7]. Intermolecular hydride delivery would then be favoured from the least sterically hindered face of the prochiral carbonyl group. 

Solladie later proposed the now favoured explanation of intramolecular hydride transfer from the DIBAL reducing agent in the absence of a chelating metal 

Steven M. Allin, Stephen J. Shuttleworth and Philip C. Bulman Page 

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