Regioselective cis,vic-dihydroxylation of α,β,γ,δ- unsaturated carboxylic esters: Enhanced γ,δ-selectivity by employing trifluoroethyl or hexafluoroisopropyl esters

Article abstract of DOI:10.1055/s-2006-951473

The regioselectivity of Sharpless asymmetric dihydroxylation (AD) of α,β,γ,δ-unsaturated carboxylic esters was studied as a function of α-, β-, and δ-substituents and for fluorine-free versus fluorinated esters. The latter showed increased or complete γ,δ-selectivities: the hexafluoroisopropyl ester being superior to the trifluoroethyl ester. Olefinations of α,β-unsaturated aldehydes with phosphorus ylide 36 or phosphonate anion 41 provided α,β, γ,δ-unsaturated trifluoroethyl esters, leading inter alia to complete trans selectivity and to 31 with 94% E selectivity, respectively. Georg Thieme Verlag Stuttgart.