- Preparation of tungsten-based olefin metathesis catalysts supported on alumina
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A new tungsten alkylidene complex, W(NAr)(CHCMe2Ph)(OHIPT- NMe2)(pyrrolide) {Ar=2,6-(i-Pr)2C6H 3; HIPT-NMe2=2,6-[2,4,6-(i-Pr)3C 6H2]2-4-NMe2-C6H 2}, has been synthesized and shown to be highly selective for Z homocoupling metathesis of selected terminal olefins in pentane, as is W(NAr)(CH2CH2CH2)(OHIPT)(pyrrolide) (5). Both 5 and W(NAr)(CHCMe2Ph)(OHIPT-NMe2)(pyrrolide) (6) are adsorbed onto calcined alumina. Control experiments and metathesis homocoupling of four substrates lead to the conclusions that 5 is largely adsorbed in a reaction that liberates HIPTOH, while 6 is adsorbed largely through an interaction between the dimethylamino group and an acidic site on the surface. There is no evidence that any adsorbed catalyst can give rise to Z selectivity of a magnitude equal to that found in a homogeneous reaction involving 5 or 6. Copyright
- Yuan, Jian,Townsend, Erik M.,Schrock, Richard R.,Goldman, Alan S.,Mueller, Peter,Takase, Michael K.
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Read Online
- Preparation and reactions of 4-iodobutyl pinacolborate. Synthesis of substituted alkyl and aryl pinacolboronates via 4-iodobutyl pinacolborate utilizing tetrahydrofuran as the leaving group
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Iodine reacts with 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (HBpin), under ambient reaction conditions in THF, to form the iodoalkylborate species 2-(4-iodobutoxy)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (4-IboxBpin). Apparently, one-half equivalent of I2 reacts with HBpin to form IBpin in pentanes, which in turn cleaves THF to form the 4-IboxBpin. Alkyl and aryl Grignard reagents, prepared under Barbier conditions, then react with 4-IboxBpin to form the corresponding alkyl and aryl pinacolboronates while reforming and liberating THF as the leaving group.
- Murphy, Chris L.,Hall, Aaron,Roberts, Emily J.,Ryan, Matthew D.,Clary, Jacob W.,Singaram, Bakthan
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p. 3032 - 3033
(2015/02/19)
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- SYNTHESIS OF BORONIC ESTERS AND BORONIC ACIDS USING GRIGNARD REAGENTS
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Boronic esters and boronic acids are synthesized at ambient temperature in an ethereal solvent by the reaction of Grignard reagents with a boron-containing substrate. The boron-containing substrate may be a boronic ester such as pinacolborane, neopentylglycolborane, or a dialkylaminoborane compound such as diisopropylaminoborane. The Grignard reagents may be preformed or generated from an alkyl, alkenyl, aryl, arylalkyl, heteroaryl, vinyl, or allyl halide compound and Mg°. When the boron-containing substrate is a boronic ester, the reactions generally proceed at room temperature without added base in about 1 to 3 hours to form a boronic ester compound. When the boron-containing substrate is a dialkylaminoborane compound, the reactions generally proceed to completion at 0°C in about 1 hour to form a boronic acid compound.
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Paragraph 0123
(2013/03/26)
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- Diastereodivergent synthesis of trisubstituted alkenes through protodeboronation of allylic boronic esters: Application to the synthesis of the californian red scale beetle pheromone
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E-allylic boronic esters undergo a highly diastereoselective protodeboronation with TBAF·3 H2O to give Z-trisubstituted alkenes. The selectivity can be switched to give predominantly the E-alkene instead by using KHF2/TsOH (see scheme). The utility of the methodology has been illustrated in a short synthesis of a component of the sex pheromone of the Californian red scale beetle. Copyright
- Hesse, Matthew J.,Butts, Craig P.,Willis, Christine L.,Aggarwal, Varinder K.
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supporting information
p. 12444 - 12448
(2013/02/23)
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- Suzuki-Miyaura cross-couplings of secondary allylic boronic esters
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Palladium-catalyzed cross-coupling reactions of secondary allylic boronic esters with iodoarenes were demonstrated under the conditions previously described for the coupling of benzylic substrates. The regioselectivity of the process was largely dictated by the pattern of olefin substitution. The Royal Society of Chemistry 2012.
- Glasspoole, Ben W.,Ghozati, Kazem,Moir, Jonathon W.,Crudden, Cathleen M.
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supporting information; experimental part
p. 1230 - 1232
(2012/02/15)
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- Reaction of grignard reagents with diisopropylaminoborane. Synthesis of alkyl, aryl, heteroaryl and allyl boronic acids from organo(diisopropyl)- aminoborane by a simple hydrolysis
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Diisopropylaminoborane (BH2-N(iPr)2) is prepared by reacting lithium diisopropylaminoborohydride (iPr-LAB) with trimethylsilyl chloride (TMSCl). Aliphatic, aromatic, and heteroaromatic (diisopropylamino) boranes are readily synthesiz
- Bailey, Christopher L.,Murphy, Chris L.,Clary, Jacob W.,Eagon, Scott,Gould, Naomi,Singaram, Bakthan
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p. 331 - 341
(2013/08/23)
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- NOVEL BORATE DERIVATIVES AND THEIR APPLICATIONS
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Borates, compositions comprising chiral (cyclic and acyclic) and achiral (cyclic and acyclic) borates; chiral (cyclic and acyclic) and achiral (cyclic and acyclic) biborates; and methods for their synthesis. Additionally, a significantly improved synthetic protocol for the synthesis of wide range of boronates starting from borates or biborates and Grignard or organolithium reagents that can be used for kilo lab and commercial scale production.
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Page/Page column 6
(2012/12/13)
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- Practical and efficient applications of novel dioxaborolanes and dioxaborinanes in the synthesis of corresponding boronates and their use in the palladium-catalyzed cross coupling reactions
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The syntheses of boronates derived from the reaction of dioxaborolanes and dioxaborinanes with either organolithium or organomagnesium reagents are investigated along with their subsequent use in the palladium cross coupling reaction. The intrinsic stability of these cyclic esters contributes to their facile reaction with both lithium and magnesium nucleophiles at mild and safe conditions. We have found that many of the reactions proceed at room temperature which is a significant improvement over the traditional routes which require cryogenic temperatures. The scope of these reactions and their practical application to large scale process synthesis is described.
- Myslinska, Malgorzata,Heise, Glenn L.,Walsh, Dana J.
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experimental part
p. 2937 - 2941
(2012/07/31)
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- Hydride as a leaving group in the reaction of pinacolborane with halides under ambient Grignard and Barbier conditions. One-pot synthesis of alkyl, aryl, heteroaryl, vinyl, and allyl pinacolboronic esters
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Grignard reagents (aliphatic, aromatic, heteroaromatic, vinyl, or allylic) react with 1 equiv of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (pinacolborane, PinBH) at ambient temperature in tetrahydrofuran (THF) to afford the corresponding pinacolboronates. The initially formed dialkoxy alkylborohydride intermediate quickly eliminates hydridomagnesium bromide (HMgBr) and affords the product boronic ester in very good yield. Hydridomagnesium bromide (HMgBr) in turn disproportionates to a 1:1 mixture of magnesium hydride (MgH2) and magnesium bromide (MgBr2) on addition of pentane to the reaction mixture. DFT calculations (Gaussian09) at the B3LYP/6-31G(d) level of theory show that disproportionation of HMgBr to MgH2 and MgBr2 is viable in the coordinating ethereal solvents. This reaction also can be carried out under Barbier conditions, where the neat PinBH is added to the flask prior to the in situ formation of Grignard reagent from the corresponding organic halide and magnesium metal. Pinacolboronic ester synthesis under Barbier conditions does not give Wurtz coupling side products from reactive halides, such as benzylic and allylic halides. The reaction between PinBH and various Grignard reagents is an efficient, mild, and general method for the synthesis of pinacolboronates.
- Clary, Jacob W.,Rettenmaier, Terry J.,Snelling, Rachel,Bryks, Whitney,Banwell, Jesse,Wipke, W. Todd,Singaram, Bakthan
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supporting information; experimental part
p. 9602 - 9610
(2012/01/03)
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