Inverted Stereoselectivity in Grignard Additions to Chiral Aldehydes by Use of Polyethers.

Publisher Website
Google Scholar
Abstract
The stereoselectivity of organimetallic additions to aldehydes and ketones with an alkoxy function at a chiral .alpha. carbon is usually explained on the basis of a chelation mechanism. The reaction of 1,2-O-isopropylidene-3-O-methyl-.alpha.-D-xylo-pentodialdo-1,4-furanose(1) with CH3MgI is an example of this. Addition of polyethers, including crown ethers, to the reaction mixture inverted the stereoselectivity and the unchelated product was formed. This observation is probably due to a complexation between the Grignard reagent and the polyether which prevents the chelation mechanism from operating.

This publication has 0 references indexed in Scilit: