- Cu-catalyzed [2 + 2 + 1] cascade annulation of vinyl iodonium salts with elemental sulfur/selenium for the modular synthesis of thiophenes and selenophenes
-
A [2 + 2 + 1] annulation protocol has been established for the modular synthesis of 2,4-disubstituted thiophenes/selenophenes, with excellent regioselectivity. The reactions have been catalyzed by copper salt with elemental sulfur and selenium serving as
- Chen, Chao,Wang, Fei,Wu, Chao,Wu, Yaxing
-
supporting information
p. 945 - 949
(2022/02/01)
-
- Rate dependence on inductive and resonance effects for the organocatalyzed enantioselective conjugate addition of alkenyl and alkynyl boronic acids to β-indolyl enones and β-pyrrolyl enones
-
Two key factors bear on reaction rates for the conjugate addition of alkenyl boronic acids to heteroaryl-appended enones: the proximity of inductively electron-withdrawing heteroatoms to the site of bond formation and the resonance contribution of available heteroatom lone pairs to stabilize the developing positive charge at the enone β-position. For the former, the closer the heteroatom is to the enone β-carbon, the faster the reaction. For the latter, greater resonance stabilization of the benzylic cationic charge accelerates the reaction. Thus, reaction rates are increased by the closer proximity of inductive electron-withdrawing elements, but if resonance effects are involved, then increased rates are observed with electron-donating ability. Evidence for these trends in isomeric substrates is presented, and the application of these insights has allowed for reaction conditions that provide improved reactivity with previously problematic substrates.
- Boylan, Amy,Li, Jian-Yuan,Lundy, Brian J.,May, Jeremy A.,Nguyen, Thien S.,Sundstrom, Sasha,Vallakati, Ravikrishna
-
-
- Synthesis of Acrylonitriles via Mild Base Promoted Tandem Nucleophilic Substitution-Isomerization of α-Cyanohydrin Methanesulfonates
-
Main observation and conclusion: We have developed an efficient synthesis of acrylonitriles via mild base promoted tandem nucleophilic substitution-isomerization of α-cyanohydrin methanesulfonates with alkenylboronic acids. This transition metal-free protocol works under simple and mild conditions and offers good chemical yields for a wide range of substrates and demonstrates good functional group tolerance. (Figure presented.).
- Liu, Shiwen,Meng, Lingling,Zeng, Xiaojun,Hammond, Gerald B.,Xu, Bo
-
p. 913 - 917
(2021/04/05)
-
- Transition-Metal-Free C(sp2)–C(sp2) Cross-Coupling of Diazo Quinones with Catechol Boronic Esters
-
A transition-metal-free C(sp2)?C(sp2) bond formation reaction by the cross-coupling of diazo quinones with catechol boronic esters was developed. With this protocol, a variety of biaryls and alkenyl phenols were obtained in good to high yields under mild conditions. The reaction tolerates various functionalities and is applicable to the derivatization of pharmaceuticals and natural products. The synthetic utility of the method was demonstrated by the short synthesis of multi-substituted triphenylenes and three bioactive natural products, honokiol, moracin M, and stemofuran A. Mechanistic studies and density functional theory (DFT) calculations revealed that the reaction involves attack of the boronic ester by a singlet quinone carbene followed by a 1,2-rearrangement through a stepwise mechanism.
- Che, Chi-Ming,Wu, Kai,Wu, Liang-Liang,Zhou, Cong-Ying
-
supporting information
p. 16202 - 16208
(2020/07/17)
-
- Synthesis, Structure and Reactivities of Pentacoordinated Phosphorus–Boron Bonded Compounds
-
The isolation and reactivities of two pentacoordinated phosphorus–tetracoordinated boron bonded compounds were explored. A highly Lewis acidic boron reagent and electron-withdrawing ligand system were required to form the pentacoordinated phosphorus state of the P–B bond. The first compound, a phosphoranyl-trihydroborate, gave a THF stabilised phosphoranyl-borane intermediate upon a single hydride abstraction in THF. This compound could undergo a unique rearrangement, which involved a two-fold ring expansion, to give a fused bicyclic compound or it could act as a mono-hydroboration reagent. The hydroboration reactivity of the intermediate was found to be higher towards alkynes vs. alkenes, with good to moderate regioselectivity towards the terminal carbon. The second compound, a phosphoranyl-triarylborate, was found to have different reactivity as it was highly stable towards acids and bases. This is thought to be due to the large bulk around the P–B bond as shown in the crystal structure.
- Havare, Nizam,Kano, Naokazu,Morokuma, Keiji,O'Brien, Nathan J.,Ramozzi, Romain,Uematsu, Ryohei
-
-
- Transition-Metal-Free Deaminative Vinylation of Alkylamines
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The amino group is one of the most fundamental structural motifs in natural products and synthetic chemicals. However, amines potential as effective alkylating agents in organic synthesis is still problematic. A unified strategy has been established for deaminative vinylation of the alkylamines with vinyl boronic acids by C?N bond activation under catalyst-free conditions. The key to the high reactivity is the utilization of pyridinium salt-activated alkylamines, with a base as a promoter. The transformation exhibits good functional group compatibility, and includes inexpensive primary amine feedstocks and amino acids. The proposed method can serve as a powerful synthetic method for late-stage modification of complex compounds. Mechanistic experiments suggest that free radical processes are involved in this system. (Figure presented.).
- Hu, Jiefeng,Cheng, Bo,Yang, Xianyu,Loh, Teck-Peng
-
p. 4902 - 4908
(2019/09/13)
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- Coupling of Trifluoroacetaldehyde N-Triftosylhydrazone with Organoboronic Acids for the Synthesis of gem-Difluoroalkenes
-
The synthesis of alkyl gem-difluoroalkenes remains a difficult task in organic synthesis. Here, we report a general and efficient approach for tackling this problem by gem-difluoroolefination of trifluoroacetaldehyde N-triftosylhydrazone with organoboronic acids. This protocol is operationally simple, free of transition metals, and suitable for a broad range of organoboronic acids. Moreover, the utility of the products was demonstrated by further conversion of the gem-difluorovinyl group.
- Ma, Yu,Reddy, Bhoomireddy Rajendra Prasad,Bi, Xihe
-
p. 9860 - 9863
(2019/12/24)
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- N -Heterocyclic Carbene-Catalyzed Olefination of Aldehydes with Vinyliodonium Salts to Generate α,β-Unsaturated Ketones
-
An organocatalyzed metal-free, direct olefination of aldehydes with vinyliodonium salts has been achieved by an N-heterocyclic carbene-promoted C-H bond activation. The reaction proceeds under very mild conditions, delivering a range of (hetero)aryl-vinyl ketones in good yields. The retention of the double bond configuration is uniformly observed, and the application of 2-methoxyphenyl auxiliary group in iodonium salts secures a complete selectivity of the vinyl transfer.
- Rajkiewicz, Adam A.,Kalek, Marcin
-
p. 1906 - 1909
(2018/04/16)
-
- Mild Base Promoted Nucleophilic Substitution of Unactivated sp3-Carbon Electrophiles with Alkenylboronic Acids
-
Diverse alkenylboronic acids react smoothly with various sp3-carbon electrophiles such as unactivated alkyl triflates in the presence of mild bases such as K3PO4. The reaction protocol is very mild and thereby enables high functional group tolerance. This transition metal-free condition is orthogonal towards the classic transition metal catalyzed Suzuki coupling. (Figure presented.).
- Liu, Shiwen,Zeng, Xiaojun,Hammond, Gerald B.,Xu, Bo
-
p. 3667 - 3671
(2018/09/12)
-
- Synthesis of α-Borylated Ketones by Regioselective Wacker Oxidation of Alkenylboronates
-
As part of a program aimed at metal-catalyzed oxidative transformations of molecules with carbon-metalloid bonds, the synthesis of α-borylated ketones is reported via regioselective TBHP-mediated Wacker-type oxidation of N-methyliminodiacetic acid (MIDA)-protected alkenylboronates. The observed regioselectivity correlates with the hemilabile nature of the B-N dative bond in the MIDA boronate functional group, which allows boron to guide selectivity through a neighboring group effect.
- Corless, Victoria B.,Holownia, Aleksandra,Foy, Hayden,Mendoza-Sanchez, Rodrigo,Adachi, Shinya,Dudding, Travis,Yudin, Andrei K.
-
supporting information
p. 5300 - 5303
(2018/09/12)
-
- NH2-directed C-H alkenylation of 2-vinylanilines with vinylbenziodoxolones
-
The first directing-group-mediated C-H alkenylation with alkenyl-λ3-iodanes as electrophilic alkene-transfer reagents has been developed. The application of free aromatic amines as challenging but synthetically valuable directing groups in combination with an IrIII catalyst enabled the synthesis of highly desirable 1, 3- dienes in excellent yields of up to 98% with high to perfect (Z, E) stereoselectivity. A broad substrate scope and further synthetic modifications are demonstrated.
- Boelke, Andreas,Caspers, Lucien D.,Nachtsheim, Boris J.
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p. 5344 - 5347
(2017/11/07)
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- Oxalyl Boronates Enable Modular Synthesis of Bioactive Imidazoles
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Described herein is the preparation of oxalyl boronate building blocks and their application for the construction of heterocycles. The oxalyl unit, readily accessible through commercially available starting materials, enables a modular approach for the synthesis of imidazoles. A variety of aromatic, heteroaromatic, and alkyl carboxaldehydes were condensed with oxalyl boronates to afford substituted boryl imidazoles in a regiocontrolled fashion. Subsequent palladium-catalyzed cross-coupling with haloarenes furnished the desired trisubstituted imidazole scaffolds. To demonstrate the utility of these scaffolds, potent inhibitors of the serine/threonine-protein kinase STK10 were synthesized.
- Lee, C. Frank,Holownia, Aleksandra,Bennett, James M.,Elkins, Jonathan M.,St. Denis, Jeffrey D.,Adachi, Shinya,Yudin, Andrei K.
-
supporting information
p. 6264 - 6267
(2017/05/19)
-
- Enantioselective Multicomponent Condensation Reactions of Phenols, Aldehydes, and Boronates Catalyzed by Chiral Biphenols
-
Chiral diols and biphenols catalyze the multicomponent condensation reaction of phenols, aldehydes, and alkenyl or aryl boronates. The condensation products are formed in good yields and enantioselectivities. The reaction proceeds via an initial Friedel-Crafts alkylation of the aldehyde and phenol to yield an ortho-quinone methide that undergoes an enantioselective boronate addition. A cyclization pathway was discovered while exploring the scope of the reaction that provides access to chiral 2,4-diaryl chroman products, the core of which is a structural motif found in natural products.
- Barbato, Keith S.,Luan, Yi,Ramella, Daniele,Panek, James S.,Schaus, Scott E.
-
supporting information
p. 5812 - 5815
(2015/12/11)
-
- An efficient synthesis of 2-(1-(E)-alkenyl)phenylphosphonates via Suzuki reaction of aryl nonaflates with (E)-1-alkenylboronates
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An efficient and general Suzuki coupling reaction between 2-phosphonylaryl nonaflates and (E)-1-alkenylboronic pinacol esters using Pd(OAc) 2/PPh3 as catalysts, K2CO3 as base and DMF as solvent has been develope
- Peng, Ai-Yun,Chen, Ba-Tian,Chen, Pei-Jiang
-
-
- Organotrifluoroborate hydrolysis: Boronic acid release mechanism and an acid-base paradox in cross-coupling
-
The hydrolysis of potassium organotrifluoroborate (RBF3K) reagents to the corresponding boronic acids (RB(OH)2) has been studied in the context of their application in Suzuki-Miyaura coupling. The "slow release" strategy in such SM couplings is only viable if there is an appropriate gearing of the hydrolysis rate of the RBF3K reagent with the rate of catalytic turnover. In such cases, the boronic acid RB(OH)2 does not substantially accumulate, thereby minimizing side reactions such as oxidative homocoupling and protodeboronation. The study reveals that the hydrolysis rates (THF, H2O, Cs2CO 3, 55 °C) depend on a number of variables, resulting in complex solvolytic profiles with some RBF3K reagents. For example, those based on p-F-phenyl, naphthyl, furyl, and benzyl moieties are found to require acid catalysis for efficient hydrolysis. This acid-base paradox assures their slow hydrolysis under basic Suzuki-Miyaura coupling conditions. However, partial phase-splitting of the THF/H2O induced by the Cs2CO 3, resulting in a lower pH in the bulk medium, causes the reaction vessel shape, material, size, and stirring rate to have a profound impact on the hydrolysis profile. In contrast, reagents bearing, for example, isopropyl, β-styryl, and anisyl moieties undergo efficient "direct" hydrolysis, resulting in fast release of the boronic acid while reagents bearing, for example, alkynyl or nitrophenyl moieties, hydrolyze extremely slowly. Analysis of B-F bond lengths (DFT) in the intermediate difluoroborane, or the Swain-Lupton resonance parameter (R) of the R group in RBF3K, allows an a priori evaluation of whether an RBF3K reagent will likely engender "fast", "slow", or "very slow" hydrolysis. An exception to this correlation was found with vinyl-BF 3K, this reagent being sufficiently hydrophilic to partition substantially into the predominantly aqueous minor biphase, where it is rapidly hydrolyzed.
- Lennox, Alastair J. J.,Lloyd-Jones, Guy C.
-
supporting information; experimental part
p. 7431 - 7441
(2012/06/16)
-
- Lithium aminoborohydrides 17. Palladium catalyzed borylation of aryl iodides, bromides, and triflates with diisopropylaminoborane prepared from lithium diisopropylaminoborohydride
-
The Alcaraz-Vaultier borylation of aryl halides and triflates is reported utilizing diisopropylaminoborane (BH2N(iPr)2) prepared from the corresponding lithium aminoborohydride (LAB reagent). BH 2N(iPr)2, prepared by reacting lithium diisopropylaminoborohydride with trimethylsilyl chloride, provided the most consistent isolated yields from this reaction. Catalytic amounts of palladium dichloride produced the highest yields from aryl iodides, while catalytic tris(dibenzylideneacetone)dipalladium(chloroform) provided the best yields for aryl bromides and triflates. This route to boronic acids is mild enough to tolerate various functionalities and for the first time employs aryl triflates as substrates for the Alcaraz-Vaultier borylation. In addition, it was found that both boronic acid and ester compounds could be isolated from the reaction mixture utilizing simple work-up procedures. Treatment of the reaction intermediate with an acid/base work-up provided the corresponding boronic acid, while treating the same intermediate with a diol, such as neopentyl glycol, afforded the corresponding boronic ester.
- Haddenham, Dustin,Bailey, Christopher L.,Vu, Chau,Nepomuceno, Gabby,Eagon, Scott,Pasumansky, Lubov,Singaram, Bakthan
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experimental part
p. 576 - 583
(2011/03/18)
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- Anomalies in the stereoselectivity of the petasis reaction using styrenyl boronic acids
-
The Petasis three-component coupling reaction of N-benzylphenylglycinol, glyoxylic acid, and styrenylboronic acids allows for the efficient synthesis of functionalized homoarylalanine derivatives. The reactions were shown to proceed in high yield but low selectivity, regardless of the nature of the substituent on the styrenylboronic acid component. Anomalies in the stereoselectivity of these reactions compared with previously reported results have been traced to the source of the organoboronic acid. Asymmetric dihydroxylation of the unsaturated amino acid derivatives enables a highly efficient route to dihydroxyhomoarylalanine derivatives. CSIRO 2011.
- Churches, Quentin I.,Johnson, James K.,Fifer, Nathan L.,Hutton, Craig A.
-
-
- Thermal and microwave hydrolysis of organotrifluoroborates mediated by alumina
-
Hydrolysis of organotrifluoroborates to the corresponding organoboronic acids is readily achieved under either thermal or microwave conditions in the presence of alumina. The organoboronic acid products are obtained in good to excellent yields with essent
- Kabalka, George W.,Coltuclu, Vitali
-
experimental part
p. 6271 - 6272
(2010/01/11)
-
- Efficient hydrolysis of organotrifluoroborates via silica gel and water
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(Chemical Equation Presented) A general, mild, and efficient method for the hydrolysis of organotrifluoroborates to unveil boronic acids using silica gel and H2O was developed. This method proved to be tolerant of a broad range of aryl-, heteroaryl-, alkenyl-, and alkyltrifluoroborates as well as structurally diverse aminomethylated organotrifluoroborates.As anticipated, electron-rich substrates provided the corresponding boronic acids more readily than electron-poor substrates, owing to the resonance-stabilized difluoroborane intermediate. The method developed was expanded further for the conversion of organotrifluoroborates to the corresponding boronate esters. 2009 American Chemical Society.
- Molander, Gary A.,Cavalcanti, Livia N.,Canturk, Belgin,Pan, Po-Shen,Kennedy, Lauren E.
-
supporting information; experimental part
p. 7364 - 7369
(2010/01/16)
-
- Lithium aminoborohydrides 16. Synthesis and reactions of monomeric and dimeric aminoboranes
-
(Chemical Equation Presented) 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 tetrahydrofuran (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°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, monomelic aminoboranes, such as BH2-N(iPr)2, can reduce nitriles in the presence of catalytic amounts of LiBH4. This BH 2-N(iPr)2/LiBH4 reducing system also reduces 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.
- Pasumansky, Lubov,Haddenham, Dustin,Clary, Jacob W.,Fisher, Gary B.,Goralski, Christian T.,Singaram, Bakthan
-
p. 1898 - 1905
(2008/09/18)
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- Facile synthesis of iodonium salts by reaction of organotrifluoroborates with p-iodotoluene difluoride
-
A simple and easy method for the synthesis of various iodonium salts was developed, and involves the reaction of potassium organotrifluoroborates with p-iodotoluene difluoride under mild conditions. The one-pot synthesis of a (Z)-(2-fluoroalkenyl)iodonium
- Yoshida, Masanori,Osafune, Kanako,Hara, Shoji
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p. 1542 - 1546
(2008/02/05)
-
- Synthesis and biological evaluation of 6,7-disubstituted 4-aminopyrido[2,3-d]pyrimidines as adenosine kinase inhibitors
-
The synthesis and structure-activity relationship of a series of 6,7-disubstituted 4-aminopyrido[2,3-d]pyrimidines as novel non-nucleoside adenosine kinase inhibitors is described. A variety of substituents, primarily aryl, at the C6 and C7 positions of the pyridopyrimidine core were found to yield analogues that are potent inhibitors of adenosine kinase. In contrast to the 5,7-disubstituted and 5,6,7-trisubstituted pyridopyrimidine series, these analogues exhibited only modest potency to inhibit AK in intact cells.
- Perner, Richard J.,Lee, Chih-Hung,Jiang, Meiqun,Gu, Yu-Gui,DiDomenico, Stanley,Bayburt, Erol K.,Alexander, Karen M.,Kohlhaas, Kathy L.,Jarvis, Michael F.,Kowaluk, Elizabeth L.,Bhagwat, Shripad S.
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p. 2803 - 2807
(2007/10/03)
-
- 2-Pyrones possessing antimicrobial and cytotoxic activities
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The 2-pyrone sub-unit is found in a number of natural products possessing broad spectrum biological activity. Such compounds are validated as being capable of binding to specific protein domains and able to exert a remarkable range of biological effects. In an effort to identify synthetic 2-pyrones with interesting biological effects, herein we report the synthesis and biological evaluation of 4-substituted-6-methyl-2-pyrones. Synthetic routes to 4-alkyl/alkenyl/aryl/alkynyl-6-methyl-2-pyrones have been developed utilising Sonogashira, Suzuki and Negishi cross-coupling starting from readily available 4-bromo-6-methyl-2-pyrone. Specific conditions for each organometallic protocol were required for successful cross-coupling. In particular, a triethylamine/acetonitrile - base/solvent mixture was crucial to Sonogashira alkynylation of 4-bromo-6-methyl-2-pyrone, whereas thallium carbonate was a mandatory base for the Suzuki cross-coupling of trialkylboranes. The 2-pyrones demonstrate potent inhibitory activity against Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Schizosaccharomyces pombe and Botrytis cinerea. The growth inhibitory activities of selected 2-pyrones were determined in A2780 human ovarian carcinoma and K562 human chronic myelogenous leukaemia cell lines using an in vitro cell culture system (MTT assay). These studies demonstrate that 4-phenylethynyl-, 4-tetrahydropyranylpropargyl ether- and 4-ethynyl-6-methyl-2-pyrones have excellent potential as a new class of anticancer agents.
- Fairlamb, Ian J. S.,Marrison, Lester R.,Dickinson, Julia M.,Lu, Feng-Ju,Schmidt, Jan Peter
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p. 4285 - 4299
(2007/10/03)
-
- Kinetic Enzymatic Resolution of Cyclopropane Derivatives
-
The kinetic enzymatic resolution of various cyclopropane derivatives was systematically investigated. The study focused on synthetically useful cyclopropylmethanols (e.g., 18a/j or 19a/j) as well as some rarely investigated cyclopropanols (e.g., 24/25 or 27). The combination of enantioselective catalytic or diastereoselective synthesis of enantiomerically enriched compounds with enzymatic approaches ultimately led to the most convenient route to enantiomerically pure starting materials. Again, this was especially proven for the synthesis of cyclopropanols 18a/j and 19a/j. Key to the successful investigation was to rigorously establish an analytical tool for the analysis of enantiomeric composition of reaction mixtures.
- Pietruszka, Joerg,Rieche, Anja C. M.,Wilhelm, Thorsten,Witt, Andreas
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p. 1273 - 1286
(2007/10/03)
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- Di(isopropylprenyl)borane: A new hydroboration reagent for the synthesis of alkyl and alkenyl boronic acids
-
The best of the old: The new hydroboration reagent 1 combines the selectivity of disiamylborane (2) with the reactivity towards carbonyls of allyl boranes 3. Conventional oxidative workup conditions are avoided, as facile hydrolysis in protic media provides the corresponding boronic acids with up to 99% anti-Markovnikov selectivities. A one-pot hydroboration/ Suzuki-Miyaura protocol adds to the synthetic value of 1.
- Kalinin, Alexey V.,Scherer, Stefan,Snieckus, Victor
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p. 3399 - 3404
(2007/10/03)
-
- Synthesis of 8-substituted xanthine derivatives by Suzuki cross-coupling reaction
-
A Suzuki cross-coupling reaction procedure was developed to prepare 8-substituted 3,7-dihydropurine-2,6-dione (xanthine) derivatives. 8-Halogen-substituted xanthines were reacted with phenyl- and styrylboronic acids. The best results were obtained using tetrakis(triphenylphosphine)palladium(0) and tripotassium phosphate in dimethylformamide. The developed procedure allows for a convergent synthesis of pharmacologically active 8-substituted xanthine derivatives.
- Vollmann, Karl,Mueller, Christa E.
-
p. 871 - 879
(2007/10/03)
-
- Palladium catalysed tandem cyclisation-anion capture. Part 8: Cascade hydrostannylation-cyclisation-anion capture and cascade hydroboration-cyclisation-anion capture on solid phase
-
Up to four bonds and five stereocentres are created, in five component processes (five point diversity), utilising resin bound aryl iodides by hydroboration or hydrostannylation of alkynes, followed by cyclisation-anion capture involving Suzuki or Stille reactions. Three small libraries were prepared to validate the chemistry.
- Grigg, Ronald,MacLachlan, William S,MacPherson, David T,Sridharan, Visuvanathar,Suganthan, Selvaratnam
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p. 10335 - 10345
(2007/10/03)
-
- Potassium alkenyl- and aryltrifluoroborates: Stable and efficient agents for rhodium-catalyzed addition to aldehydes and enones
-
(matrix presented). Potassium alkenyl- and aryltrifluoroborates undergo addition to enones and aldehydes in the presence of Rh(I) catalysts to give β-functionalized ketones and allylic/benzylic alcohols, respectively. Reaction proceeds more rapidly than with the corresponding boronic acids, and the choice of phosphine ligand does not signifcantly influence the overall efficiency of addition.
- Batey, Robert A.,Thadani, Avinash N.,Smil, David V.
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p. 1683 - 1686
(2008/02/09)
-
- H NMR evidence for the formation of vinyllead triacetates. The reactions of vinylmercury, vinyltin, and vinylboronic acids with lead tetraacetate
-
Vinylmercury compounds, vinylboronic acids and vinylstannanes undergo rapid metal-lead exchange with lead tetraacetate in deuterochloroform to generate vinyllead triacetates, which have been characterised by their 1H-1H and 207Pb-1H coupling constants. In addition, a number of divinyl and mixed aryl-vinyllead dicarboxylates have been prepared via boron-lead exchange.
- Parkinson, Christopher J.,Stoermer, Martin J.
-
p. 207 - 214
(2007/10/03)
-
- Lithium bis(ethylenedioxyboryl)methide and its reactions with carbonyl compounds and with the chlorotriphenyl derivatives of germanium, tin and lead
-
Transesterification of tris(dimethoxyboryl)methane, HC[B(OCH3)2]3, with ethylene glycol yielded tris(ethylenedioxyboryl)methane (I), HC(BO2C2H4)3 which with methyllithium in THF at -70°C precipitated lithium bis(ethylenedioxyboryl)methide (II), Li+ HC(BO2C2H4)2-. Reaction of II with Ph3MCl, where M = Ge, Sn, or Pb, gave Ph3MCH(BO2C2H4)2. The analogous 1,3-propanediol ester, Li+HC(BO2C3H6)2-, yielded Ph3MCH(BO2C3H6)2. Treatment of Ph3SnCH(BO2C2H4)2 with MeLi followed by Ph3SnCl gave (Ph3Sn)2CHBO2C2H4, showing that one B and one Sn atom are sufficient to stabilize a carbanion. Reaction of II with aldehydes gave high yields of 1-alkene-1-boronic esters, RCHCHBO2C2H4, with unexpectedly high stereoselectivity, 90-100% trans by NMR analysis. Aqueous work-up of these boronic esters yielded the boronic acids, RCHCHB (OH)2, which crystallized as the pure trans isomers. Ketones react with II in an analogous manner. The reaction with acetophenone was not stereospecific. Functional group compatibility has been demonstrated in condensations of II with 1,3-dichloroacetone, cinnamaldehyde, p-nitrobenzaldehyde, and p-dimethylaminobenzaldehyde. The trans geometry of the major isomer of CH3CHCHBO2C2H4 was proved by B-butylation with butyllithium followed by rearrangement with iodine and base to form cis-2-heptene, a sequence of known stereochemistry, and analogous structure proofs were carried out with cis-CH3CHCHBO2C2H4 and trans-C6H5CHCHBO2C2H4.
- Matteson, Donald S.,Jesthi, Pradipta K.
-
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