27839-90-3Relevant articles and documents
Steric effects in the diastereoselective reduction of β-ketosulfones
Grossert, J. Stuart,Dharmaratne, H. Ranjith W.,Cameron, T. Stanley,Vincent, Beverly R.
, p. 2860 - 2869 (2007/10/02)
The stereochemical course of the reduction of ketones adjacent to a chiral center normally shows some diastereoselectivity (described by Cram's rule), the degree of which is dependent on the structure of the ketone and on the reaction conditions; the selectivity in acyclic species is often not very great.In this paper, we described the sodium borohydride reduction of four acyclic β-ketosulfones, containing a chiral center at the α-position, in which the products are formed with high diastereoselectivity.Reasons for this selectivity became apparent when we were able to show that these ketosulfones apparently exist predominantly in the same conformation in solution as in the solid state.This conformation requires that the preferred trajectory for nucleophilic attack on the carbonyl group leads to reaction on the re face, to yield the threo diastereomer of the β-hydroxysulfone.The results that led to these conclusions were obtained from stuctural studies by X-ray crystallography, as well as by detailed 1H and 13C nuclear magnetic resonance spectroscopy.In some cases, the latter spectra were run both in solution and in the solid state.
