Asymmetric Dihydroxylation Of Olefins Research Articles

Molybdenum-catalyzed asymmetric anti-dihydroxylation of allylic alcohols

Asymmetric dihydroxylation of alkenes is one of the fundamental reactions in organic synthesis, but the anti-dihydroxylation is much less developed than its syn-variant. Here we report a highly enantio- and diastereoselective anti-dihydroxylation of allylic alcohols by using a chiral molybdenum-bishydroxamic acid complex as catalyst and environmentally benign hydrogen peroxide as oxidant. This reaction enables the construction of the 1,2,3-triol structural unit in high enantio- and diastereocontrol starting from simple allylic alcohol precursors. Our reaction complements the Sharpless dihydroxylation not only in its diastereoselectivity, but also in regiocontrol. The mechanistic studies indicate that this dihydroxylation reaction consists of an initial enantioselective epoxidation and the following in situ regioselective ring opening, both of which are promoted by the molybdenum-catalyst.

ChemInform Abstract: Engineering Rieske Non‐Heme Iron Oxygenases for the Asymmetric Dihydroxylation of Alkenes

The asymmetric dihydroxylation of olefins is of special interest due to the facile transformation of the chiral diol products into valuable derivatives. Rieske non-heme iron oxygenases (ROs) represent promising biocatalysts for this reaction as they can be engineered to efficiently catalyze the selective mono- and dihydroxylation of various olefins. The introduction of a single point mutation improved selectivities (≥95 %) and conversions (>99 %) towards selected alkenes. By modifying the size of one active site amino acid side chain, we were able to modulate the regio- and stereoselectivity of these enzymes. For distinct substrates, mutants displayed altered regioselectivities or even favored opposite enantiomers compared to the wild-type ROs, offering a sustainable approach for the oxyfunctionalization of a wide variety of structurally different olefins.

Engineering Rieske Non-Heme Iron Oxygenases for the Asymmetric Dihydroxylation of Alkenes.

The asymmetric dihydroxylation of olefins is of special interest due to the facile transformation of the chiral diol products into valuable derivatives. Rieske non-heme iron oxygenases (ROs) represent promising biocatalysts for this reaction as they can be engineered to efficiently catalyze the selective mono- and dihydroxylation of various olefins. The introduction of a single point mutation improved selectivities (≥95 %) and conversions (>99 %) towards selected alkenes. By modifying the size of one active site amino acid side chain, we were able to modulate the regio- and stereoselectivity of these enzymes. For distinct substrates, mutants displayed altered regioselectivities or even favored opposite enantiomers compared to the wild-type ROs, offering a sustainable approach for the oxyfunctionalization of a wide variety of structurally different olefins.

ChemInform Abstract: Stereoselective Reactions. Part 19. Asymmetric Dihydroxylation of Olefins by Employing Osmium Tetroxide-Chiral Amine Complexes.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Preclusion of the “Second Cycle” in the Osmium-Catalyzed Asymmetric Dihydroxylation of Olefins Leads to a Superior Process.

ChemInform Abstract: Preclusion of the “Second Cycle” in the Osmium-Catalyzed Asymmetric Dihydroxylation of Olefins Leads to a Superior Process.

ChemInform Abstract: New Ligands Double the Scope of the Catalytic Asymmetric Dihydroxylation of Olefins.

ChemInform Abstract: New Ligands Double the Scope of the Catalytic Asymmetric Dihydroxylation of Olefins.

ChemInform Abstract: Synthesis of Chiral 2,3-Disubstituted 1,4-Diazabicyclo(2.2.2)octane. New Ligand for the Osmium-Catalyzed Asymmetric Dihydroxylation of Olefins.

Abstract Chiral 2,3-disubstituted 1,4-diazabicyclo[2.2.2]octane (DABCO) derivatives have been synthesized and utilized as a chiral ligand for the osmium-catalyzed asymmetric dihydroxylation of olefins. Optically active diols in up to 41%ee are obtained in good yields.

ChemInform Abstract: Polymeric Cinchona Alkaloids for the Heterogeneous Catalytic Asymmetric Dihydroxylation of Olefins: The Influence of the Polymer Backbone Polarity on the Compatibility Between Polymer Support and Reaction Medium.

Abstract Heterogeneous catalytic asymmetric dihydroxylation of olefins using homo- and co-polymeric cinchona alkaloids has been reported. The benzoate type homopolymers 2a, b showed high enantioselectivity in the heterogeneous ADH reactions, but their catalytic efficiency was largely dependent on the solvent system which may relate to the accessibility of the active catalytic site. The influence of polymer backbone polarity on the compatibility with the reaction medium was investigated using copolymers 3a, b and 4 having polar polymer backbone. The reaction rates and optical yields were dramatically increased by increasing the polarity of the polymer backbone in NMO- acetone H 2 O system.

Green chemistry and catalysis

Green chemistry and catalysis

Asymmetric Dihydroxylation of Alkenes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Clean Osmium‐Catalyzed Asymmetric Dihydroxylation of Olefins in Ionic Liquids and Supercritical CO2 Product Recovery.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An Economical, Highly Efficient and Recyclable Catalyst System for Asymmetric Dihydroxylation of Olefins

A reusable cinchona alkaloid derivative ligand, which could be easily synthesized by two step transformation with cheap 3,6-dichloropyridazine and quinine as materials, was applied to homogeneous asymmetric dihydroxylation of olefins with NMO as co-oxidant in Me2CO-H2O system and the products could be extracted with Et2O from the recyclable catalyst system. 80%–93% yield and 51%–99% ee have been obtained. When trans-stilbene was chosen as the substrate for recycling experiment, 88%–92% yield and > 99% ee have been obtained for ten recycles.

A Triazine Core for a New Class of Sharpless Asymmetric Dihydroxylation Ligands.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Osmylated Macroporous Cinchona Alkaloid Resins: Highly Efficient and Recyclable Catalysts for Asymmetric Dihydroxylation of Olefins

A simple method for simultaneous recovery and reuse of OsO 4 and alkaloid ligand in the asymmetric dihydroxylation of olefins has been developed by usin g macroporous alkaloid resins bearing residual vinyl groups.

Osmium-catalyzed asymmetric dihydroxylation of olefins in ionic liquidsThe effect of the chiral ligand structure on recyclability

Abstract Effective osmium-catalyzed asymmetric dihydroxylation was observed with 1,4-bis(9-O-diquininyl)phthalazine, (DQ)2PHAL, as the chiral ligand in the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6]. It was shown that the ligand undergoes dihydroxylation during the reaction, affording a more polar ligand which remains in the ionic liquid phase, when the latter is extracted with diethyl ether, thus facilitating catalyst recycling. In contrast, when 1,4-bis(9-O-dihydroquininyl)phthalazine, (DHQ)2PHAL, which cannot undergo dihydroxylation, was used as the chiral ligand, the catalyst was extracted into the organic layer.

A triazine core for a new class of Sharpless asymmetric dihydroxylation ligands

Sharpless asymmetric dihydroxylation ligands were synthesized using a triazine spacer group in two, high yielding steps from cheap, readily available starting materials. The ligands, gave good enantioselectivities in the asymmetric dihydroxylation of alkenes and may provide a very economic alternative to current systems.

A Soluble Block Copolymer-Supported bis-Cinchona Alkaloid Ligand for the Asymmetric Dihydroxylation of Olefins

A soluble block copolymer-supported ligand was prepared via polycondensation of a bis-cinchona alkaloid derivative, polyethylene glycol, and terephthaloyl chloride. Its application in the asymmetric dihydroxylation of olefins delivered very good enantioselectivity.

Microencapsulated Osmium Tetroxide‐Catalyzed Asymmetric Dihydroxylation of Olefins in Water Without Using Organic Cosolvents.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Catalytic asymmetric dihydroxylation of olefins with reusable OsO(4)(2-) on ion-exchangers: the scope and reactivity using various cooxidants.

Exchanger-OsO(4) catalysts are prepared by an ion-exchange technique using layered double hydroxides and quaternary ammonium salts covalently bound to resin and silica as ion-exchangers. The ion-exchangers with different characteristics and opposite ion selectivities are specially chosen to produce the best heterogeneous catalyst that can operate using the various cooxidants in the asymmetric dihydroxylation reaction. LDH-OsO(4) catalysts composed of different compositions are evaluated for the asymmetric dihydroxylation of trans-stilbene. Resin-OsO(4) and SiO(2)-OsO(4) designed to overcome the problems associated with LDH-OsO(4) indeed show consistent activity and enantioselectivity in asymmetric dihydroxylation of olefins using K(3)Fe(CN)(6) and molecular oxygen as cooxidants. Compared to the Kobayashi heterogeneous systems, resin-OsO(4) is a very efficient catalyst for the dihydroxylation of a wide variety of aromatic, aliphatic, acyclic, cyclic, mono-, di-, and trisubstituted olefins to afford chiral vicinal diols with high yields and enantioselectivities irrespective of the cooxidant used. Resin-OsO(4) is recovered quantitatively by a simple filtration and reused for a number of cycles with consistent activity. The high binding ability of the heterogeneous osmium catalyst enables the use of an equimolar ratio of ligand to osmium to give excellent enantioselectives in asymmetric dihydroxylation in contrast to the homogeneous osmium system in which excess molar quantities of the expensive chiral ligand to osmium are invariably used. The complexation of the chiral ligand (DHQD)(2)PHAL, having very large dimension, a prerequisite to obtain higher ee, is possible only with the OsO(4)(2-) located on the surface of the supports.

ChemInform Abstract: Osmium‐Catalyzed Asymmetric Dihydroxylation of Olefins by H2O2: Dual Role of the Cinchona Alkaloid Ligand.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.