Hydroboration Of Styrenes Research Articles

Boraalkenes Made by a Hydroboration Route: Cycloaddition and B=C Bond Cleavage Reactions.

Hydroboration of styrene or vinylcyclohexane with the IMes(C6 F5 )BH+ cation followed by deprotonation provided a convenient synthetic entry to the [B]=CHCH2 R boraalkenes 9 a and 9 b. The in situ generated IMes(SCN)BH+ system reacted similarly with 1,1-diphenylethene followed by deprotonation to give the isothiocyanato substituted boraalkene 9 c. The boraalkenes underwent [2+2] cycloaddition reactions with a small series of heterocumulenes to give the respective four-membered heterocycles. The [B]=CHCH2 R+CO2 cycloadducts 13 a and 13 b added the borane HB(C6 F5 )2 with cleavage of the central B-C σ-bond. CS2 underwent an unusual reaction with the boraalkenes, namely insertion into the B=C bond with formation of the borylated dithioketene acetal under complete rupture of the strong B=C double bond. The intermediate dithiobora-β-lactone type intermediate was isolated in the case of the isothiocyanato-boraalkene reaction and characterized by X-ray diffraction.

Magnetically active iron oxide nanoparticles for catalysis of organic transformations: A review

Magnetic iron oxide nanoparticles (MIONPs) are an efficient retrievable catalytic system recognized for their broad applications in numerous fields, including pharmaceutical, nanobiotechnology, and many more. Eco-friendly reusable, inexpensive, superparamagnetic nano sizes are the main reasons for its use in various fields. Several examples are available in the literature wherein MIONPs have been exploited as efficient nanocatalysts for organic transformations. There is no review available focusing on MIONPs catalyzed organic transformation except for coupling reactions only. Thus, the present review article focuses on the compendious account of various MIONPs reported catalyzing organic transformation, including synthesis of bioactive compounds, C–C, C–N, C–O, C–S, and S–S coupling, C–H arylation, hydroboration of styrene, oxidation of m-cresol and Friedel-Crafts benzoylation reactions. In addition, the synthetic routes employed to date for modification and functionalization of MIONPs for making them suitable for catalysis have been discussed in detail with schematic illustrations. The future of catalysis lies in the lucid design and construction of the novel, highly active, and reusable magnetic iron nanocomposite catalysts that would ultimately cover the pathway to establish green and sustainable technologies. This review will be enlightening for the researchers in designing novel functionalized MIONPs for sustainable developments.

Cobalt(I) Complexes of 5-Aryl-2-iminopyrrolyl Ligands: Synthesis, Spin Isomerism, and Application in Catalytic Hydroboration.

This work reports the first successful isolation and full characterization of cobalt(I) complexes of 5-aryl-2-iminopyrrolyl ligands. In one approach, when [Co{κ2 N,N'-5-(2,4,6-R3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}(Py)Cl] (R = iPr, 1a; R = Ph, 1b) were reacted with K(HBEt3) or Na(Hg) in toluene, the Co(I) arene complexes [Co{κ2 N,N'-5-(2,4,6-iPr3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}(η6-C6H5CH3)] (2a) and [ Co{κ2 N,N'-5-[2'-(κ:η6- C6H5)-C6H2-4',6'-Ph2]-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}] (2b) were formed. The reaction of complex 1a with KC8 in Et2O yielded the [Co{κ2 N,N'-5-(2,4,6-iPr3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}]2 (3). On another approach, the metathesis of potassium 5-(2,4,6-triisopropylphenyl)-2-( N-2,6-diisopropylphenylformimino)pyrrolyl (KLa) with CoCl(PMe3)3 yielded the bis(trimethylphosphine) complex [Co{κ2 N,N'-5-(2,4,6-iPr3-C6H2)-NC4H2-2-C(H)═N(2,6-iPr2-C6H3)}(PMe3)2] (4) in a good yield. Complexes 2a, 3, and 4 are paramagnetic, high-spin species, while 2b is a diamagnetic complex. Compound 2b exhibited a spin isomerism behavior ( S = 0 ↔ S = 1) as determined by variable-temperature 1H NMR experiments (Δ H° = 7.7 kcal mol-1), being also supported by computational studies (Δ E = 4.2 kcal mol-1). All complexes were tested in the hydroboration of styrene with pinacolborane (HBPin), with complex 4 exclusively yielding the respective anti-Markovnikov addition product. Additionally, all complexes catalyzed the fast and quantitative hydroboration of benzaldehyde with HBPin.

Hierarchical hybrid MnO/Pd-Fe3O4 and CoO/Pd-Fe3O4 nanocomposites as efficient catalysts for hydroboration of styrene

We report a one-pot synthesis of hierarchical MnO/Pd-Fe3O4 and CoO/Pd-Fe3O4 nanocomposites containing scrolled multilayered nanosheets by controlled thermal decomposition of Fe(CO)5 and reduction of metal precursors [Pd(OAc)2]. During the synthetic process, particles of amorphous MnO and CoO are immobilized on the Pd-Fe3O4 support. These hierarchical nanocomposites follow a stepwise growth mechanism, initially forming Pd-Fe3O4 seeds aggregated from nuclei, followed by growth to produce multilayered MnO/Pd-Fe3O4 or CoO/Pd-Fe3O4 structures. To the best of our knowledge, this is the first report on the hydroboration of styrene with bis(pinacolato)diboron using heterogeneous nanocatalysts. Among these catalysts, CoO/Pd-Fe3O4 nanocomposites showed excellent performance due to the presence of a dual Pd and CoO catalytic system.

Iron-Catalyzed Asymmetric Hydroboration of Styrenes

Iron-Catalyzed Asymmetric Hydroboration of Styrenes

ChemInform Abstract: Beyond Benzyl Grignards: Facile Generation of Benzyl Carbanions from Styrenes.

AbstractAn efficient protocol for generation of benzylic carbanion is developed based on hydroboration of styrenes with bulky pinacol borane followed by sterically induced cleavage of the C—B bond using KOtBu.

Selective copper-promoted cross-coupling reaction of anilines and alkylboranes

Extension of the Chan–Lam N-alkylation of anilines by using alkylboranes as organoboron partners is reported. Alkylboranes, synthesized by hydroboration of styrenes, are effectively coupled with anilines, which comprises a facile method for the synthesis of highly functionalized phenethylaniline derivatives. This is the first time that alkylboranes are used in C–N copper-promoted cross-coupling reactions.

ChemInform Abstract: Catalytic Asymmetric Hydroboration with Oxazaborolidines.

Abstract The cyclic secondary boranes derived from ephedrine and pseudoephedrine undergo rhodium complex-catalysed hydroboration of styrenes; both the regiochemistry and derived enantiomeric excess depend strongly on the structure of the catalyst with the ferrocenebiphosphine complex (12d) the most promising to date.

ChemInform Abstract: Highly Regio‐ and Enantioselective Copper‐Catalyzed Hydroboration of Styrenes.

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Highly Regio‐ and Enantioselective Copper‐Catalyzed Hydroboration of Styrenes

In the introduction to this Communication, the third sentence in the first paragraph on p. 6178 should read as follows: “ so far, only combinations of rhodium complexes and catecholborane (CatBH) have shown the desirable high regioselectivity and enantioselectivity.4,5 ”. The authors wish to add references [4 c] and [14 b]. The full references appear below.

Highly Regio‐ and Enantioselective Copper‐Catalyzed Hydroboration of Styrenes

In der Einleitung dieser Zuschrift muss der dritte Satz im ersten Absatz auf S. 6178 wie folgt enden: “ ; so far, only combinations of rhodium complexes and catecholborane (CatBH) have shown the desirable high regioselectivity and enantioselectivity.[4,5] ” Die Autoren möchten überdies die Literaturzitate [4c] und [14b] ergänzen. Die vollständigen Literaturstellen 4 und 14 sind hier angegeben.

Highly Regio‐ and Enantioselective Copper‐Catalyzed Hydroboration of Styrenes

Die Suche nach effizienten regioselektiven Katalysatorsystemen, die mit stabilen Hydroborierungsreagentien verträglich sind und durch den Einsatz nichtracemischer Liganden enantioselektiv gestaltet werden können, führte zu Kupfer(I)-Komplexen mit chelatisierenden Phosphanliganden, die die regio- und enantioselektive Hydroborierung von Styrolen mit Pinakolboran (PinBH) unter Bildung der verzweigten Boronsäureester bei Raumtemperatur katalysieren (siehe Beispiel). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Highly Regio‐ and Enantioselective Copper‐Catalyzed Hydroboration of Styrenes

Highly Regio‐ and Enantioselective Copper‐Catalyzed Hydroboration of Styrenes

Lithium Aminoborohydrides 16. Synthesis and Reactions of Monomeric and Dimeric Aminoboranes

Aminoboranes are synthesized in situ from the reaction of the corresponding lithium aminoborohydrides (LABs) with methyl iodide, trimethylsilylchloride (TMS-Cl), or benzyl chloride under ambient conditions. In hexanes, the reaction using methyl iodide produces aminoborane and methane, whereas in tetrahydro-furan (THF) this reaction produces amine-boranes (R1R2HN:BH3) as the major product. The reaction of iPr-LAB with TMS-Cl or benzyl chloride yields exclusively diisopropylaminoborane [BH2-N(iPr)2] in THF as well as in hexanes at 25 degrees C. Diisopropylaminoborane and dicyclohexylaminoborane exist as monomers due to the steric requirement of the alkyl group. All other aminoboranes studied are not sterically hindered enough to be monomers in solution, but instead exist as a mixture of monomers and dimers. The dimers are four-membered rings formed through boron-nitrogen coordination. In general aminoboranes are not hydroborating reagents. However, monomeric aminoboranes, such as BH2-N(iPr)2, can reduce nitriles in the presence of catalytic amounts of LiBH4. This BH2-N(iPr)2/LiBH4 reducing system also re-duces ketones, aldehydes, and esters. Diisopropylaminoborane, synthesized from iPr-LAB, can be converted into boronic acids by a palladium-catalyzed reaction with aryl bromides. Aminoboranes derived from heterocyclic amines, such as pyrrole, pyrazole, and imidazole, can be prepared by the direct reaction of borane/tetrahydrofuran (BH3:THF) with these heterocyclic amines. It has been reported that pyrazole-derived aminoborane forms a six-membered dimer through boron-nitrogen coordination, where as, pyrrolylborane forms a dimer through boron-hydrogen coordination. Pyrrolylborane monohydroborates both alkenes and alkynes at ambient temperatures. Hydroboration of styrene with pyrrolylborane followed by hydrolysis gives the corresponding boronic acid, 2-phenylethylboronic acid, in 40% yield. Similarly phenylacetylene is mono-hydroborated by pyrrolylborane, to give E-2-phenylethenylboronic acid in 50% yield.

Synthesis of JOSIPHOS‐Type Ligands via a Diastereoselective Three‐Component Reaction and Their Application in Asymmetric Rhodium‐Catalyzed Hydroborations.

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.

Synthesis, reactivity and catalytic properties of rhodium complexes of ( R,R)-1-benzyl-3,4-dithioetherpyrrolidines

Complexes [Rh(cod)(degusR)]ClO 4, where cod is 1,5-cyclooctadiene and degusR represents the homochiral dithioethers ( R,R)-1-benzyl-3,4-bis(methylsulfanyl)pyrrolidine, ( R,R)-1-benzyl-3,4-bis(isopropylsulfanyl)pyrrolidine and ( R,R)-1-benzyl-3,4-bis(phenylsulfanyl)pyrrolidine were prepared and characterized. Their reactivity with CO and PPh 3 was investigated. The complexes were assayed as catalysts in hydroformylation of styrene, hydrogenation of acrylic acids and hydroboration of styrene. Although these complexes containing dithioethers behave as catalytic precursors in hydroformylation reaction, the results suggest that mononuclear hydride rhodium carbonyl species is responsible for the catalytic activity. The cationic complexes are not active in the hydrogenation of acrylic acids in the conditions tested. These complexes are moderately active in the hydroboration of styrene with catecholborane, but their selectivities are not satisfactory.

ジアルコキシポランによるスチレンの選択的ハイドロポレーション

ジアルコキシポランによるスチレンの選択的ハイドロポレーション