- DYNAMIC NMR SPECTROSCOPY OF THE TETRAVALENT ORGANOBORATE COMPOUNDS. SYNTHESIS AND SOME UNIQUE FEATURES OF ORGANOBORATES CONTAINING THE C6H4CH2NMe2-2 LIGAND
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Novel borates (ArBMe3)Li*OEt2 (I), (ArBEt)Li*OEt2 (II) and (BArPh-9-BBn)Li*OEt2 (III) (Ar=C6H4NMe2-2, 9-BBN=9-borabicyclononyl) were synthesized in the reactions of ArLi with BMe3, BEt3 and BPh-9-BBN, respectively.Detailed studies were made of 1H,
- Kalbarczyk, E.,Pasynkiewicz, S.
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- A versatile synthesis of 9-BBN derivatives from organometallic reagents and 9-(triisopropylsilyl)thio-9-borabicyclo[3.3.1]nonane
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Representative B-substituted-9-BBNs (3) are efficiently prepared from either organolithium or Grignard reagents through their addition to (TIPS)S- 9-BBN (1) which is readily available from TIPSSH and 9-BBN-H. The thermally induced collapse of the intermediate 'ate' complexes (2) produces 3 which is easily isolated in good yield and high purity. (C) 2000 Elsevier Science Ltd.
- Soderquist, John A.,Justo De Pomar, Jorge C.
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- Palladium-catalyzed 1,3-diol fragmentation: Synthesis of ω-dienyl aldehydes
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2-(1′-Hydroxy-2′-propenyl)cycloalkan-1-ols 1 undergo dehydrative C1-C2 bond cleavage and provide ω-dienyl aldehydes 2 under the catalysis of Pd(0) and 9-phenyl-9-BBN. The Royal Society of Chemistry.
- Kimura, Masanari,Mori, Masahiko,Tamaru, Yoshinao
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- Selective Boryl-Anion Migration in a Vinyl sp2?sp3 Diborane Induced by Soft Borane Lewis Acids
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An intramolecular 1,2-boryl-anion migration from boron to carbon has been achieved by selective activation of the π system in [(vinyl)B2Pin2)]? using “soft” BR3 electrophiles (BR3=BPh3 or 9-aryl-BBN). The soft character is key to ensure 1,2-migration proceeds instead of oxygen coordination/B?O activation. The BR3-induced 1,2-boryl-anion migration represents a triple borylation of a vinyl Grignard reagent using only B2Pin2 and BR3 and forms differentially protected 1,1,2-triborylated alkanes. Notably, by increasing the steric bulk at the β position of the vinyl Grignard reagent used to activate B2Pin2, 1,2-boryl-anion migration can be suppressed in favor of intermolecular {BPin}? transfer to BPh3, thus enabling simple access to unsymmetrical sp2?sp3 diboranes.
- Fasano, Valerio,Cid, Jessica,Procter, Richard J.,Ross, Emily,Ingleson, Michael J.
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- New Method for the Synthesis of Organoboranes
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Mixed organoboranes can be conveniently prepared in a single stage by treatment of a dialkylborane with various lithium dialkyl- or diaryl-cuprates.
- Whiteley, Chris G.
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- “Inverse” Frustrated Lewis Pairs: An Inverse FLP Approach to the Catalytic Metal Free Hydrogenation of Ketones
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For the first time have boron-containing weak Lewis acids been demonstrated to be active components of Frustrated Lewis Pair (FLP) catalysts in the hydrogenation of ketones to alcohols. Combining the organosuperbase (pyrr)3P=NtBu with the Lewis acid 9-(4-CF3-C6H4)-BBN generated an “inverse” FLP catalyst capable of hydrogenating a range of aliphatic and aromatic ketones including N-, O- and S-functionalized substrates and bio-mass derived ethyl levulinate. Initial computational and experimental studies indicate the mechanism of catalytic hydrogenation with “inverse” FLPs to be different from conventional FLP catalysts that contain strong Lewis acids such as B(C6F5)3.
- Mummadi, Suresh,Brar, Amandeep,Wang, Guoqiang,Kenefake, Dustin,Diaz, Rony,Unruh, Daniel K.,Li, Shuhua,Krempner, Clemens
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supporting information
p. 16526 - 16531
(2018/10/20)
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- Suzuki-miyaura cross-coupling reactions of unactivated alkyl halides catalyzed by a nickel pincer complex
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A nickel(II) pincer complex, [(MeN2N)Ni-Cl], was used to catalyze alkyl-alkyl and alkyl-aryl Suzuki-Miyaura coupling reactions of unactivated alkyl halides. The coupling of 9-alkyl-9-borabicyclo[3.3.1]nonane and 9-phenyl-9-borabicyclo[3.3.1]nonane reagents with alkyl halides was achieved in modest to good yields. The reactions tolerated a variety of useful functional groups including ester, ether, furan, thioether, acetal, and Boc groups. Georg Thieme Verlag Stuttgart, New York.
- Di Franco, Thomas,Boutin, Nicolas,Hu, Xile
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p. 2949 - 2958
(2013/11/06)
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- Asymmetric sulfur ylide reactions with boranes: Scope and limitations, mechanism and understanding
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The reactions of aryl-stabilized sulfur ylides with organoboranes has been studied under a variety of conditions. At 5 or -78°C, the reaction with Et3B gave a mixture of the first and second homologation products, but at -100°C, only the first homologation product was obtained even with just 1.1 equiv of Et3B. Under these optimized conditions, the chiral sulfur ylides (derived from camphor sulfonic acid) with different aryl groups were reacted with Et3B to give the corresponding alcohols (95-98% yield, 96-98% ee) and amines (74-77% yield, >98% ee). The origin of the high enantioselectivity is discussed. The use of nonsymmetrical 9-BBN derivatives was also explored. It was found that whereas primary alkyl substituents gave mixtures of products derived from competing migration of the boron substituent and the boracycle, all other groups resulted in either exclusive migration of the boron substituent (Ph, hexenyl, i-Pr) or exclusive migration of the boracycle (hexynyl, cyclopropyl). The factors responsible for the outcome of the reactions involving a hindered (i-Pr) and an unhindered (propynyl) substituent were studied by DFT calculations. This revealed that, in the case of an unhindered substituent, the conformation of the ate complex is the dominant factor whereas, in the case of a hindered substituent, the barriers to interconversion between the conformers of the ate complex and subsequent migration control the outcome of the reaction.
- Fang, Guang Y.,Wallner, Olov A.,Di Blasio, Nadia,Ginesta, Xavier,Harvey, Jeremy N.,Aggarwal, Varinder K.
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p. 14632 - 14639
(2008/09/17)
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- Is phenyl a good migrating group in the rearrangement of organoborates generated from sulfur ylides?
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Calculations show that the unexpected low phenyl migratory aptitude observed in reactions of mixed alkyl-aryl boranes with benzylic sulfur ylides can be attributed to (1) a conformational issue, (2) the reduction of the usual neighbouring effect of the phenyl in the transition state by the benzylic nature of the migrating terminus, (3) steric hindrance suffered by the larger phenyl group migrating to the hindered migrating terminus and this despite (4) the increase in the barrier to alkyl migration by the presence of a 'non-migrating' phenyl on the boron atom. The Royal Society of Chemistry 2006.
- Robiette, Raphael,Guang, Yu Fang,Harvey, Jeremy N.,Aggarwal, Varinder K.
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p. 741 - 743
(2008/02/03)
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- Ring expansion-annulation strategy for the synthesis of substituted azulenes and oligoazulenes. 2. Synthesis of azulenyl halides, sulfonates, and azulenylmetal compounds and their application in transition-metal-mediated coupling reactions
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A "ring expansion-annulation strategy" for the synthesis of substituted azulenes is described based on the reaction of β'-bromo- α-diazo ketones with rhodium carboxylates. The key transformation involves an intramolecular Buechner reaction followed by β-elimination of bromide, tautomerization, and in situ trapping of the resulting 1-hydroxyazulene as a carboxylate or triflate ester. Further synthetic elaboration of the azulenyl halide and sulfonate annulation products can be achieved by employing Heck, Negishi, Stille, and Suzuki coupling reactions. Reaction of the azulenyl triflate 84 with pinacolborane provides access to the azulenylboronate 91, which participates in Suzuki coupling reactions with alkenyl and aryl iodides. The application of these coupling reactions to the synthesis of biazulenes, terazulene 101, and related oligoazulenes is described, as well as the preparation of the azulenyl amino acid derivative 110.
- Crombie, Aimee L.,Kane Jr., John L.,Shea, Kevin M.,Danheiser, Rick L.
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p. 8652 - 8667
(2007/10/03)
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