The reaction of (2S,S-S)-alpha-(1-hydroxyethyl)vinyl sulfoxide with alkyl radicals and tributyltin hydride gave the addilion-hydrogenation products with high diastereoselectivity, whereas (2R,S-S)-alpha-(-1-hydroxyethyl)vinyl sulfoxide gave no products under similar conditions. An important role of intramolecular hydrogen bonding for the diastereoselectivity as well as the reactivity toward alkyl radicals is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.
Diastereoselective radical allylation and hydrogenation of α-(arylsulfinyl)alkyl radicals induced by chelation control
The radical allylation and the hydrogenation of α-(arylsulfinyl)alkyl radicals were examined. In the presence of a bidentate Lewis acid, high diastereoselectivities were achievable in the allylation and the hydrogenation of α-(arylsulfinyl)alkyl radicals derived through the radical β-addition to vinyl sulfoxides bearing the 2-pyridyl, the imidazol-2-yl, or the benzimidazol-2-yl groups.