Desymmetrisation of meso difuryl alcohols, diols and their derivatives: complementary directed and undirected asymmetric dihydroxylation reactions

摘要

Asymmetric reactions (for example, asymmetric epoxidation and asymmetric dihydroxylation) were examined for thendesymmetrisation of the meso substrates 1,1-difuran-2-ylmethanol, N-(1,1-difuran-2-ylmethyl)-4-methylbenzene-nsulfonamide, (R,S)-1,4-difuran-2-ylbutane-1,4-diol and the derivatives of these compounds. The complex OsO4u0001(S,S)-nS )-1,2-diphenyl-N,Nu0001-bis(2,4,6-trimethylbenzyl)ethane-1,2-diamine was found to be an effective reagent for thendesymmetrisation of meso-1,2-bis(3,6-dihydro-3-hydroxy-2H-pyran-2-yl)ethanes and the corresponding di-p-nmethoxybenzoates by asymmetric dihydroxylation. The stereochemical outcome of this process depends criticallynon the relative stereochemistry and substitution of the substrate, and can occur anti to, or be directed by, an allylicnalcohol or p-methoxybenzoyloxy functional group.