The acid accelerated ruthenium-catalysed dihydroxylation. Scope and limitations

Abstract

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.

Studies on the Total Synthesis of Lactonamycin: Synthesis of the Fused Pentacyclic B–F Ring Unit

“…Finally, the reaction was conducted at -45°C and only trace amounts of quinone 23 were detected; pure quinone 6 was obtained in 60 % yield ( Unfortunately, attempted dihydroxylation of quinone 6 under the conditions previously described by Danishefsky (N-methylmorpholine N-oxide in the presence of 3.25 mol-% OsO 4 ) [5,6b] or by using stoichiometric quantities of OsO 4 led to complete decomposition. Additionally, attempted dihydroxylation with ruthenium chloride and sodium periodate [25] was also unsuccessful, despite being applied earlier to other lactonamycin intermediates. Finally, attempted dihydroxylation under Sharpless conditions [26] also failed (Scheme 6).…”

Palladium-catalyzed cross-couplings of allylic carbonates with triarylbismuths as multi-coupling atom-efficient organometallic nucleophiles

“…1,3-disubstituted propenes are important skeletons found in natural products [40][41][42][43]. These compounds are also useful for a variety of synthetic transformations [44][45][46][47][48][49].…”

Enantioselective Synthesis of Natural Polyoxygenated Cyclohexanes and Cyclohexenes from [(p‐Tolylsulfinyl)methyl]‐p‐quinols

“…mCPBA oxidation of the sulfoxide to the sulfone (98 %) was followed by stereoselective DIBALH reduction (99 %), secondary OH protection and elimination of MeSO 2 pTol (Cs 2 CO 3 , 87 % for the two steps) to give the cyclohexenone (4S,6R)-24, [12] while epoxidation under the conditions described above (Ph 3 The synthesis of the other natural target bearing a cyclohexane structure-(À)-gabosine O (6)-only required the diastereoselective cis-dihydroxylation of the double bond of cyclohexenone (4R,6S)-24 and deprotection of the alcohol (Scheme 6). When (4R,6S)-24 was treated with RuCl 3 / NaIO 4 , [44] however, an inseparable 58:42 mixture of diaste- The p-facial diastereoselectivities of OsO 4 dihydroxylations are normally governed by steric factors, [17,45] and the bulky OTBDMS protecting group in 24 was slightly favouring dihydroxylation anti to the vicinal OTBDMS substituent. On the other hand, the diastereoselectivity of OsO 4 dihydroxylation of free allylic cyclohexenols has been shown to be dependent on the reactive conformation and the possibility of hydrogen bonding.…”