A Highly Efficient Procedure for Ruthenium Tetroxide Catalyzed Oxidative Cyclizations of 1,5‐Dienes

Abstract

Keywords:Oxidative cyclization / Tetrahydrofurans / Ruthenium / Oxidation / CatalysisWe report a highly efficient procedure for the oxidative cyclization of 1,5-dienes, which generally allows for high yields and selectivities. A solid-supported terminal oxidant and a finely tuned solvent mixture have both been identified as critical factors for this high efficiency. As little as 0.2 mol-% ruthenium(III) chloride as a pre-catalyst for the ruthenium te-

Sequential Catalysis: A Metathesis/Dihydroxylation Sequence

“…[15] Following these observations, we attempted a one-pot RCM/dihydroxylation using catalyst 1. A variety of dienes were treated with 1 mol % of 1 in dichloromethane under reflux conditions.…”

“…A variety of ruthenium sources, such as RuCl 3 , [12] RuO 2 , [13] [RuCl 2 (dppp) 2 ] (dppp = 1,3-bis(diphenylphosphanyl)propane), [14] [RuCl 2 (PPh 3 ) 3 ], [15] [Ru(acac) 3 ] (acac = acetylacetonate) [15] TPAP (tetrapropylammonium perruthenate), [15] and Ru/C, [15] have been used for the formation of the oxidative species RuO 4 in different oxidation reactions. [16] The method of choice for dihydroxylation of olefins is in situ formation from a catalytic amount of RuCl 3 ·3 H 2 O using NaIO 4 as the stoichiometric oxidant.…”

The Absolute Configuration of the Pyrrolosesquiterpenoid Glaciapyrrol A

“…[6] The further synthesis of glaciapyrrol A was performed as outlined in Scheme 5. The reported Ru-catalysed oxidative cyclisation [5] of geranyl benzoate in THF/CH 2 Cl 2 (9:1) selectively yielded 14 bb, whereas the same reaction in THF/ CH 2 Cl 2 (1:1) resulted in a mixture of 14 bb and 14 ba (d.r. 1.5:1) that can be separated by column chromatography.…”

“…Stark and co-workers described a Ru-catalysed method for the synthesis of tetrahydrofurans that can be used for the preparation of all four diastereomeric aldehydes from geraniol or nerol, respectively. [5] It is intriguing that these four isomers are chemically accessible starting from two acyclic terpenoid (E)-and (Z)-diastereoisomers, similar as discussed above for the biosynthetic pathways to the four isomers of 1. In this sense the Ru-catalysed cyclisation can be regarded as biomimetic.…”

Ein doppelt Donor‐aktivierter Ruthenium(VII)‐Katalysator: Synthese enantiomerenreiner THF‐Diole

“…In Schema 1 ist diese Synthesestrategie der diastereoselektiven direkten oxidativen Cyclisierung (Reaktionspfad B) gegenübergestellt. Ausgehend von unseren vorangegangenen Untersuchungen [10,11] TPAP ist ein etablierter Katalysator für die hoch chemoselektive Oxidation primärer und sekundärer Alkohole zu Carbonylverbindungen. Auch eine Reihe von Bishomoallylalkoholen (5-Hydroxyalkenen) wurde ohne jegliche Addition oder Cyclisierung an die C-C-Doppelbindung sauber in die entsprechenden Carbonylverbindungen umgewandelt.…”