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

Abstract

Asymmetric reactions (for example, asymmetric epoxidation and asymmetric dihydroxylation) were examined for the desymmetrisation of the meso substrates 1,1-difuran-2-ylmethanol, N-(1,1-difuran-2-ylmethyl)-4-methylbenzenesulfonamide, (R,S)-1,4-difuran-2-ylbutane-1,4-diol and the derivatives of these compounds. The complex OsO₄·(S,S)-1,2-diphenyl-N,N′-bis(2,4,6-trimethylbenzyl)ethane-1,2-diamine was found to be an effective reagent for the desymmetrisation of meso-1,2-bis(3,6-dihydro-3-hydroxy-2H-pyran-2-yl)ethanes and the corresponding di-p-methoxybenzoates by asymmetric dihydroxylation. The stereochemical outcome of this process depends critically on the relative stereochemistry and substitution of the substrate, and can occur anti to, or be directed by, an allylic alcohol or p-methoxybenzoyloxy functional group.