Samarium mediated pinacol coupling of carbonyl compounds in the presence of a catalytic amount of iodine under aqueous media

In the presence of a catalytic amount of iodine, metallic samarium mediated pinacol coupling of carbonyl compounds has been carried out under saturated aqueous NH4Cl-THF conditions at room temperature. It gives corresponding 1,2-diols in good yields.     

Tandem aminoxylation-allylation reactions: a rapid, asymmetric conversion of aldehydes to mono-substituted 1,2-diols

A facile and rapid synthesis of enantiopure mono-substituted 1,2-diols was achieved by the tandem aminoxylation-allylation reactions of aldehydes.     

Sequential use of regio- and stereoselective lipases for the efficient kinetic resolution of racemic 1-(5-phenylfuran-2-yl)ethane-1,2-diols

Possible routes for the enzymatic transformation of various substituted 1-(5-phenylfuran-2-yl)ethane-1,2-diols and their mono- and diacetylated counterparts were studied. Combining the regioselectivity of LPS mediated acylation of the starting racemic diols, the stereoselectivity of LAK shown in the enantiomer selective transformation of the previously formed racemic primary acetates and the LPS mediated mild hydrolysis-alcoholysis of the resolution products, an efficient preparative scale procedure for the synthesis of various highly enantiomerically enriched (R)- and (S)-phenylfuran-2-yl-ethane-1,2-diols has been developed.     

Selective monofluorination of diols using DFMBA

Selective monofluorination of 1,2- and 1,3-diols was achieved by reaction with DFMBA. The method is applicable for the synthesis of optically-active fluorohydrin derivatives.     

Regioselective synthesis of 1,2- and 1,3-diols from ω-hydroxy allyl acetates and carbonates via Pd complexes using boric acid and trialkyl borates

The synthesis of 1,2- and 1,3-diols and derivatives has been achieved from ω-hydroxy π-allyl palladium complexes by using boric acid and trialkyl borates.     

Copper ion-induced activation and asymmetric benzoylation of 1,2-diols: kinetic chiral molecular recognition

New catalytic ability of copper(II) ion has been exploited for monobenzoylation of 1,2-diols. The catalyst can be readily modified by ligation to acquire higher stereoselectivity. Highly effective kinetic resolution of dl-1,2-diols was achieved. The enantiodiscrimination process was clearly shown to be controlled by the kinetics of acylation of dl-1,2-diols. The catalytic method was successfully applied to asymmetric desymmetrization of meso-hydrobenzoin.     

Kinetic resolution of diols and pyridyl alcohols by Cu(II)(borabox)-catalyzed acylation

[reaction: see text] Boron-bridged bisoxazoline (borabox) ligands have been used in the copper(II)-catalyzed benzoylation of pyridyl alcohols and 1,2-diols. Efficient kinetic resolution of 1,2-diols was achieved using both borabox and bisoxazoline (box) ligands. Borabox ligands induced high selectivities in the benzoylation of suitable pyridyl alcohols, where they outperformed bisoxazolines. In addition, highly enantioselective Cu(II)(borabox)-catalyzed benzoylation has been used for the synthesis of both enantiomers of a pyridyl alcohol.     

Convenient synthesis of ethylene carbonates from carbon dioxide and 1,2-diols at atmospheric pressure of carbon dioxide

An efficient and convenient synthesis of ethylene carbonates was achieved by the reaction of carbon dioxide with 1,2-diols in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), followed by treatment with 1-bromobutane. This DBU-promoted transformation proceeded at an atmospheric pressure of carbon dioxide at 25 °C and gave ethylene carbonates in good yields.     

Synthesis and Glycosidic Reaction of 1,2-Anhydromanno-, Lyxo-, Gluco-, and Xylofuranose Perbenzyl Ethers

ABSTRACT

Stereospecific synthesis of 1,2-anhydromanno-, lyxo-, gluco-, and xylofuranose perbenzyl ethers was successfully achieved via intramolecular S _N2 reaction of the corresponding C-1 alkoxide with C-2 bearing tosyloxy group. The key intermediates, furanose 2-sulfonates, were prepared from the corresponding 1,2-diols and tosyl chloride under phase transfer conditions in good yields. Condensation of the anhydro sugars with 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose or N-benzyloxycarbonyl L-serine methyl ester in the absence of catalyst gave 1,2-trans-linked glycofuranosides in high yield.     

Thioamination of Alkenes with Hypervalent Iodine Reagents

An efficient thioamination of alkenes mediated by iodine(III) reagents is described. The use of different sulfur nucleophiles allows the flexible synthesis of 1,2‐aminothiols from alkenes. By employing chiral iodine(III) reagents, a stereoselective version of the thioamination protocol has also been developed.     

Stereoelectronic effects in the reactions of conformationally restricted,substituted cyclohexane-1,2-diones with 1,2-diols

The asymmetric synthesis of a C₂-symmetric cyclic 1,2-diketone is reported along with investigations into its properties as a potential asymmetric protecting group for 1,2-diols as the corresponding 1,2-diacetal.     

Total synthesis of (+)-blastmycinone and formal synthesis of (+)-antimycin A3b

The formal synthesis of (+)-antimycin A_3b and the total synthesis of (+)-blastmycinone were achieved using, as a key step, a method developed by us for the synthesis of 2-methyl-1,3-diols via Ti(III)-mediated diastereo- and regioselective opening of trisubstituted 2,3-epoxy alcohols, to carry out the stereoselective construction of the hydroxy-acid segment. An interesting intramolecular radical translocation took place during the epoxide opening process transforming its vicinal PMB-ether in situ, into an ‘1,2-O-(p-methoxy)benzylidene’ ring.     

Azide/oxygen photocatalysis with homogeneous and heterogeneous photocatalysts for 1,2-aminohydroxylation of acyclic/cyclic alkenes and Michael acceptors

Homogeneous as well as heterogeneous photocatalysts that are able to oxidize the azide anion with low competitive singlet oxygen quantum yields are used to generate azidyl radicals. These radicals add to electron-rich as well as electron-poor (Michael acceptors) alkenes, and carbon radicals are formed regioselectively. Trapping with triplet oxygen (type I photooxygenation) is diffusion controlled, and the initially formed peroxy radicals are reduced with regeneration of the photocatalyst. Fluorescence quenching studies reveal rapid photoinduced electron transfer in the first catalysis step. The lack of rearrangement products in the bicyclic terpene series (pinenes, limonene) accounts for rapid subsequent oxygen trapping and back electron transfer steps. The 1,2-azidohydroperoxidation enables synthesis of 1,2-azidoalcohols and 1,2-aminoalcohols by different reduction protocols. Substrate modification and combination of type II photooxygenation with electron transfer photocatalysis allows the synthesis of 1-amino-2,3-diols and 2-amino-1,3-diols.     

Cycloalumination of allylbenzenes with triethylaluminum in the presence of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>. One-pot synthesis of 2-benzylbutane-1,4-diols as precursors of dibenzylbutane lignans

One-pot synthesis of 2-[(hydroxy- and methoxyphenyl)methyl]butane-1,4-diols in an overall yield of 60–65% by cycloalumination of allylbenzenes (4-allyl-1-methoxybenzene, 4-allyl-1,2-dimethoxybenzene, 5-allyl-2-methoxyphenol, and 5-allyl-1,2,3-trimethoxybenzene) with triethylaluminum in the presence of Cp₂ZrCl₂ is reported for the first time. The developed procedure opens a new synthetic route to practically important β-substituted butane-1,4-diols that are precursors to dibenzylbutane lignans.     

Catalytic monosilylation of 1,2-diols

The selective monosilylation of 1,2-diols catalyzed by dimethyltin dichloride was successfully developed. This procedure was applied to various 1,2-diols, giving monosilylated products in good to excellent yields with high chemoselectivity.     

Epoxide hydrolase-catalyzed enantioselective synthesis of chiral 1,2-diols via desymmetrization of meso-epoxides. lzhao@diversa.com

The discovery, from nature, of a diverse set of microbial epoxide hydrolases is reported. The utility of a library of epoxide hydrolases in the synthesis of chiral 1,2-diols via desymmetrization of a wide range of meso-epoxides, including cyclic as well as acyclic alkyl- and aryl-substituted substrates, is demonstrated. The chiral (R,R)-diols were furnished with high ee's and yields. The discovery of the first microbial epoxide hydrolases providing access to complementary (S,S)-diols is also described.     

Catalytic monoalkylation of 1,2-diols

A catalytic monoalkylation of 1,2-diols by using a weak base has been developed. Copper(II) dichloride and boronic acids are effective catalysts for activating 1,2-diols in the presence of potassium carbonate as a base. Various 1,2-diols were selectively monoalkylated with allyl-, benzyl- and alkyl- halides in DMF by choosing a suitable catalyst for each 1,2-diols.     

Catalytic Enantioselective Synthesis of anti-Vicinal Silylboronates by Conjunctive Cross-Coupling

Chiral 1,2-bimetallic reagents are useful motifs in synthetic chemistry. Although syn-1,2-bimetallic compounds can be prepared by alkene dimetallation, anti-1,2-bimetallics are still rare. The stereospecific 1,2-metallate shift that occurs during conjunctive cross-coupling is shown to enable a practical and modular approach to the catalytic synthesis of enantioenriched anti-1,2-borosilanes. In addition to reaction development, the synthetic utility of anti-1,2-borosilanes was investigated, including applications to the synthesis of anti-1,2-diols and anti-1,2-amino alcohols     

Preparation of furans from alkynols utilizing palladium catalyzed intramolecular addition of alcohol to acetylene as a key reaction

A procedure is described for the synthesis of furans from 3-alkyn-1,2-diols or 2-methoxy-3-alkyn-1-ols by palladium catalyzed intramolecular addition of alcoholic moiety to acetylene linkage followed by elimination of water or methanol. The intermediary 3-furylpalladiums can be trapped with allyl halides affording 3-allylfurans in good yields.     

(Triisopropylsilyl)acetaldehyde acetal as a novel protective group for 1,2-diols

(Triisopropylsilyl)acetaldehyde dimethyl acetal (TIPS-ADMA) was synthesized from chlorotriisopropylsilane in three steps. Cyclic and acyclic 1,2-diols can be transformed to (triisopropylsilyl)ethylidene acetals (TIPS-AA). Removal of the acetal by LiBF₄ regenerates the starting diol in excellent yield even in the presence of an acetonide of 1,2-diol. The TIPS-AA group can survive under the deprotection conditions of the acetonide in acetic acid at 80 °C. Selective protection of 2,3- and 4,6-diols for O-methyl d-mannoside with TIPS-ADMA and selective deprotection of the acetals have been achieved.