The first directed reduction of beta-alkoxy ketones to anti-1,3-diol monoethers: Identification of spectator and director alkoxy groups

[GRAPHICS] A new reduction procedure for the stereoselective reduction of certain beta -alkoxy ketones is described. The method relies upon electron-transfer redu ction using samarium diiodide in THF with MeOH as an additive. Reduction is facile for a number of alkoxy groups that can complex samarium effectively but is not observed with TBS or benzyl protecting groups. Experiments with deuterated methanol show that the stereoselectivity arises from protonatio n of a samarium carbanion intermediate.