Diastereoselectivities in Reductions of α-Alkoxy Ketones Are Not Always Correlated to Chelation-Induced Rate Acceleration

Abstract The chelation-control model is used to predict stereochemical outcomes of many organometallic reactions. Diastereoselectivity arises due to reaction with a chelated intermediate with sterically differentiated faces. Earlier studies with dimethylmagnesium established that the chelated interm...

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Bibliographic Details
Published inSynthesis (Stuttgart) Vol. 51; no. 1; pp. 296 - 302
Main Authors Bartolo, Nicole D., Hornstein, Alana L., Zhao, Annie Y., Woerpel, K. A.
Format Journal Article
LanguageEnglish
Published Stuttgart · New York Georg Thieme Verlag 01.01.2019
Subjects
stereoselectivity
chelation control
hydride reductions
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Summary:Abstract The chelation-control model is used to predict stereochemical outcomes of many organometallic reactions. Diastereoselectivity arises due to reaction with a chelated intermediate with sterically differentiated faces. Earlier studies with dimethylmagnesium established that the chelated intermediate is a minor component of the reaction mixture, so reaction with the chelated intermediate must be faster than reaction with a non-chelated intermediate. High diastereoselectivity and chelation-induced rate acceleration are correlated with some hydride reducing agents. There are examples in which diastereoselectivity is high, but chelation-induced rate acceleration is not observed, however. In other cases, chelation-induced rate acceleration is observed, but diastereoselectivity remains low. These experiments illustrate that a revision to the chelation-control model is needed.
ISSN:0039-7881
1437-210X
DOI:10.1055/s-0037-1610381