Osmium-catalyzed asymmetric dihydroxylation of olefins by H2O2; dual role of the cinchona alkaloid ligand.
[reaction: see text]. A novel application of the cinchona alkaloid derivative (DHQD)2PHAL in the osmium-catalyzed asymmetric dihydroxylation of olefins is presented. In a triple catalytic system using H2O2 as the terminal oxidant, the alkaloid ligand has a dual function in providing stereocontrol in the addition step and, via its N-oxidized form, acting as reoxidant for the in situ generated osmium(VI). The formation of the N-oxide is catalyzed by a biomimetic flavin.
Jonsson
S Y
SY
Department of Organic Chemistry, Stockholm University, SE-106 91 Stockholm, Sweden.
Adolfsson
H
H
Bäckvall
J E
JE