Catalytic Asymmetric Dihydroxylation Reaction Research Articles

Aggregation-Induced Catalysis: Asymmetric Catalysis with Chiral Aggregates.

So far, there have been 4 methods to control chirality including the use of chiral auxiliaries, reagents, solvents, and catalysts documented in literature and textbooks. Among them, asymmetric catalysts are normally divided into homogeneous and heterogeneous catalysis. In this report, we present a new type of asymmetric control-asymmetric catalysis via chiral aggregates that would not belong to the above categories. This new strategy is represented by catalytic asymmetric dihydroxylation reaction of olefins in which chiral ligands are aggregated by taking advantage of typical aggregation-induced emission systems containing tetrahydrofuran and H2O cosolvents. It was proven that the chiral induction can be enhanced from er of 78:22 to 97:3 simply by changing the ratios of these 2 cosolvents. The formation of chiral aggregates of asymmetric dihydroxylation ligands, (DHQD)2PHAL and (DHQ)2PHAL, has been proven by aggregation-induced emission and a new analytical tool-aggregation-induced polarization established by our laboratory. In the meanwhile, chiral aggregates were found to be formed either by adding NaCl into tetrahydrofuran/H2O systems or by increasing concentrations of chiral ligands. The present strategy also showed promising reverse control of enantioselectivity in the Diels-Alder reaction. This work is anticipated to be extended broadly to general catalysis, especially to asymmetric catalysis in the future.

Synthesis of a New Chiral Nonracemic C2‐Symmetric 2,2′‐Bipyridyl Ligand and Its Application in Copper(I)‐Catalyzed Enantioselective Cyclopropanation Reactions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of a new chiral nonracemic C(2)-symmetric 2,2'-bipyridyl ligand and its application in copper(I)-catalyzed enantioselective cyclopropanation reactions.

An efficient synthesis of a low molecular weight, chiral nonracemic and C(2)-symmetric bipyridyl ligand is reported. The ligand was prepared using a catalytic asymmetric dihydroxylation reaction of a pyrindine as a key step. The ligand was evaluated in the asymmetric copper(I)-catalyzed cyclopropanation reactions of a series of alkenes and diazoesters. Very high diastereoselectivities and enantioselectivities were observed (>95:5 dr and up to 99% ee). These are the highest reported stereoselectivities for a chiral bipyridyl ligand. [structure: see text]

An enantioselective synthesis of the C 1C 9 segment of antitumor macrolide peloruside A

A stereocontrolled synthesis of the C 1C 9 segment of the marine natural product peloruside A is described. The key steps involve Sharpless's catalytic asymmetric dihydroxylation reaction, a chelation-controlled reduction of chiral β-alkoxy ketones to elaborate the syn-1,3-diol functionality and a ring-closing olefin metathesis of a homoallylic alcohol-derived acrylate ester to form an α,β-unsaturated δ-lactone.

ChemInform Abstract: Process Development of the Sharpless Catalytic Asymmetric Dihydroxylation Reaction to Prepare Methyl (2R,3S)‐2,3‐Dihydroxy‐3‐phenylpropionate.

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.

Process Development of the Sharpless Catalytic Asymmetric Dihydroxylation Reaction To Prepare Methyl (2R,3S)-2,3-Dihydroxy-3-phenylpropionate

A typical Sharpless catalytic asymmetric dihydroxylation (ADH) process to make methyl (2R,3S)-2,3-dihydroxy-3 phenylpropionate has been successfully developed. The ADH reaction was exothermic and complete in 2−3 h without affecting the optical purity and yield. The major impurity of methyl (2R)-hydroxy-3-keto-phenylpropionate, which may seriously damage the quality of diol, has been identified and removed properly in the process.

Syntheses of four d- and l-hexoses via diastereoselective and enantioselective dihydroxylation reactions

An expeditious approach to various protected hexoses has been developed by the use of the Sharpless catalytic asymmetric dihydroxylation reaction. Applying the Sharpless catalytic asymmetric dihydroxylation reaction on vinylfuran, diols with high enantioexcess are produced. The resulting diols can be stereoselectively transformed into either protected d- or l-mannose in five steps and approximately 39% yield from furfural. Similarly, both d- and l-talose and gulose have been synthesized in 19% overall yields, respectively. Using a modified strategy, both protected d- and l-gulo- and allo-sugar-δ-lactones were synthesized in eight steps and ∼20% overall yield from furfural.

Sharpless asymmetric dihydroxylation of 5-aryl-2-vinylfurans: application to the synthesis of the spiroketal moiety of papulacandin D.

[formula: see text] Using the Sharpless catalytic asymmetric dihydroxylation reaction on 5-aryl-2-vinylfurans, diols are produced in high enantioexcess. The resulting diols can be efficiently transformed into the spiroketal ring precursor of the antifungal compound papulacandin D. Stereoselective reduction of this precursor followed by a diastereoselective dihydroxylation completes the synthesis of a mannopyranoside isomer of a papulacandin derivative.

A soluble polymer-bound approach to the Sharpless catalytic asymmetric dihydroxylation (AD) reaction: Preparation and application of a [(DHQD) 2PHAL-PEG-OMe] ligand

The synthesis of a soluble polymer-bound (DHQD) 2PHAL ligand 1 and its successful application in the catalytic asymmetric dihydroxylation reaction are described. The results highlight that the soluble polymer-bound ligand approach offers all the benefits associated with insoluble supports but with the key advantages of increased reactivity and enantioselectivity inherent with solution-phase methodology.

Synthesis of Tuckolide, a New Cholesterol Biosynthesis Inhibitor.

Tuckolide (decarestrictine D), a 10-membered lactone isolated from P. corylophilum and polyporus tuberaster fungi that potently inhibits cholesterol biosynthesis, was synthesized. The key steps include a Sharpless catalytic asymmetric dihydroxylation reaction (AD) of the methoxymethyl (MOM) ether protected diene 2 and a direct Corey-Nicolaou lactonization reaction of seco-acid 1with added silver perchlorate. The selectivity of the dihydroxylation step was found to be highly dependent on the nature of the protecting group adjacent to the diene in 2. The selectivity of the asymmetric dihydroxylation reaction of 2 indicates that both steric and electronic effects can lead to significant amounts of the undesired isomers. This synthesis establishes the absolute stereochemistry of tuckolide showing the C3 hydroxyl bearing carbon with an S-configuration comparable in an absolute sense to that in the lactone portion of the HMG-CoA reductase inhibitor compactin.

ChemInform Abstract: Anomalous Enantioselectivity in the Sharpless Catalytic Asymmetric Dihydroxylation Reaction of 1,1‐Disubstituted Allyl Alcohol Derivatives.

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.

Anomalous enantioselectivity in the Sharpless catalytic asymmetric dihydroxylation reaction of 1,1-disubstituted allyl alcohol derivatives

The Sharpless asymmetric dihydroxylation (AD) reaction has been examined on a number of 1,1-disubstituted allyl alcohol derivatives. In the majority of substrates studied, the product diols had ee's in the 11–91% range and had absolute stereochemistry opposite to that predicted using the Sharpless steric model.