Diastereoselective radical hydrogenation of alpha-(1-hydroxyalkyl)vinyl sulfoxides and sulfones controlled by intramolecular hydrogen bonding

The reaction of (S)-alpha-(1-hydroxyallryl)vinyl sulfoxides (S)-5 with alky l radicals and, tributyltin hydride gave the addition-hydrogenation product s with high diastereoselectivity, whereas the reaction with (R)-alpha-(1-hy droxyalkyl)vinyl sulfoxides (R)-5 resulted in complete recovery of the star ting sulfoxides. Stereoselective intramolecular hydrogen bonding between th e hydroxy group and the diastereotopic sulfonyl oxygen led to high diastere oselectivity in the radical reaction of alpha-(1-hydroxyethyl)vinyl sulfone 12. An important role of intramolecular hydrogen bonding on the diastereos electivity as well as the reactivity toward alkyl radicals is discussed.