AN ORGANOMETALLIC APPROACH TO PEROXYKETALS

A new method for peroxyketal synthesis is presented based upon formation of carbon-carbon bonds in the presence of a protected hydroperoxide. The 2-methoxypropyl perketal of 4(S)-hydroperoxy-2(E)-nonenal (2) undergoes reaction with a variety of metal hydrides and organometallic reagents to produce 4-peroxy 2-enols in good to excellent yields via chemoselective addition to the carbonyl carbon. Oxidation of the allylic alcohol to the 4-peroxy 2-enone is followed by deprotection to furnish a single enantiomer of a 4-hydroxyperoxy 2(E)-enone. Photochemical isomerization by the method of Snider induces spontaneous cyclization to epimeric 3-hydroxy-1,2-dioxins (hydroxy endoperoxides). Acidic methanolysis furnishes readily separable diastereomeric perketals as single enantiomers.