| Abstract: | New mono‐quaternized allyl bromide salts of bis‐Cinchona alkaloid ligands, (QD)2PHAL‐Allyl]Br and (QN)2PHAL‐Allyl]Br, have been synthesized which can be converted into their highly water‐soluble multihydroxylated derivatives under asymmetric dihydroxylation (AD) conditions and, thus, easily recovered by a simple extraction method after reaction and reused. These mono‐quaternized ligands exhibited superior catalytic efficiency to their neutral counterparts such as (DHQD)2PHAL and (DHQ)2PHAL for the AD reactions of mono‐ and disubstituted styrenes under Upjohn conditions. Merely 0.1 mol % of osmium was enough to complete the reactions of mono‐ and disubstituted styrenes and, moreover, these ligands showed the highest enantioselectivities (e.g., for styrene, 97 % ee with (QD)2PHAL‐Allyl]Br) among those ever achieved under Upjohn conditions. |
