Recently, we discovered a significant rate acceleration in RuO4-catalysed dihydroxylations of olefins by addition of Bronsted-acids resulting in a reduction of the catalyst loading to only 0.5 mol%. The present paper gives a full account on the optimisation protocol that led to the discovery of the beneficial influence of protic acids. A strong focus is set on the detailed description of the influence of different reaction parameters on both reactivity and selectivity. In the second part an intense investigation of scope and limitations will be presented. The results provided in this manuscript might lead to a deeper understanding of competing processes that influence the selectivity in RuO4-catalysed dihydroxylations.
Alcohols
Alcohols Q 0230The Acid Accelerated Ruthenium-Catalyzed Dihydroxylation. Scope and Limitations. -The present paper describes the RuO 4 -catalyzed dihydroxylation of olefins. A wide range of different olefins are oxidized in good to excellent yields using the catalyst in a loading of only 0.5mol% together with a Broenstedt-acid. The interplay of ruthenium-and acid concentration allows even the dihydroxylation of acid labile alkenes like (Ia) and (VI). However, stabilized tri-and tetrasubstituted olefins can not be converted to the diols. Advantages of the present dihydroxylation protocol are the lower costs and toxicity of the reagents. -(PLIETKER*, B.; NIGGEMANN, M.; POLLRICH, A.; Org.
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