- γ-Carboline synthesis enabled by Rh(iii)-catalysed regioselective C-H annulation
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A redox-neutral Rh(iii)-catalyzed C-H annulation of indolyl oximes was developed. Relying on the use of various alkynyl silanes as the terminal alkyne surrogates, the reaction exhibited a reverse regioselectivity, thus giving an exclusive and easy way for the synthesis of a wide range of substituent free γ-carbolines at C3 position with high efficiency. Deuterium-labelling experiments and kinetic analysis have preliminarily shed light on the working mode of this catalytic system. This journal is
- Jiang, Bo,Jia, Jingwen,Sun, Yufei,Wang, Yichun,Zeng, Jing,Bu, Xiubin,Shi, Liangliang,Sun, Xiaoying,Yang, Xiaobo
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supporting information
p. 13389 - 13392
(2020/11/10)
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- Propargylic C(sp3)-H Bond Activation for Preparing η3-Propargyl/Allenyl Complexes of Yttrium
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Propargylic C(sp3) - H bond activation of 1-substituted-1-propynes, such as 1-trimethylsilyl-1-propyne, 2-hexyne, and 1-phenyl-1-propyne, was achieved by treatment with an alkylyttrium complex 8 bearing an ene-diamido ligand to give the corresponding (η3-propargyl/allenyl)yttrium complexes 7a-c. A unique delocalized η3-propargyl/allenyl structure of these three complexes was revealed by NMR spectroscopy and X-ray single crystal analyses. To elucidate the reactivity of the η3-propargyl/allenyl unit of complexes 7a-c, we conducted two reactions with N-methylaniline and N,N′-dicyclohexylcarbodiimine. For protonation by N-methylaniline, we found that the product distribution of monosubstituted internal alkynes and allenes depended on the substituent on the η3-propargyl/allenyl moiety: 7a and 7b afforded the corresponding internal alkynes as the major products, whereas the major protonation product of 7c was phenylallene. For the insertion of N,N′-dicyclohexylcarbodiimine, complex 7a selectively yielded η3-{N,N′-dicyclohexyl-2-(3-trimethylsilylpropargyl)amidinate}yttrium 12a, while complex 7c produced η3-{N,N′-dicyclohexyl-2-(1-phenylallenyl)amidinate}yttrium complex 13c, though complex 7b gave a mixture of η3-{N,N′-dicyclohexyl-2-(3-normalpropylpropargyl)amidinate}yttrium complex 12b and η3-{N,N′-dicyclohexyl-2-(1-normalpropylallenyl)amidinate}yttrium 13b in an 83:17 ratio. On the basis of the product distributions in these two-types of reactions, (η3-propargyl/allenyl)yttrium complexes were shifted into preferentially favorable η1-allenyl species or η1-propargyl species depending on the substituents prior to the reaction with electrophiles via a four-membered cyclic mechanism.
- Nagae, Haruki,Kundu, Abhinanda,Tsurugi, Hayato,Mashima, Kazushi
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p. 3061 - 3067
(2017/09/05)
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- Synthesis of 2,3-disubstituted indenones by cobalt-catalyzed [3+2] annulation of: O -methoxycarbonylphenylboronic acid with alkynes
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Treatment of alkynes with o-methoxycarbonylphenylboronic acid in the presence of a cobalt catalyst resulted in the corresponding 2,3-disubstituted indenones in good yields. Excellent regioselectivities were observed, when silyl aryl alkynes were used. The intermediate 3-silyl-2-aryl-substituted indenones were converted to 2,3-diaryl indenones by a three-step protocol involving C-Si bromination and Suzuki-Miyaura coupling reaction.
- Ueda, Mitsuhiro,Ueno, Tamami,Suyama, Yuki,Ryu, Ilhyong
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supporting information
p. 13237 - 13240
(2016/11/17)
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- Preparative synthesis via continuous flow of 4,4,5,5-tetramethyl-2-(3- trimethylsilyl-2-propynyl)-1,3,2-dioxaborolane: A general propargylation reagent
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A scalable process for the preparation of 4,4,5,5-tetramethyl-2-(3- trimethylsilyl-2-propynyl)-1,3,2-dioxaborolane from trimethylsilylpropyne, isopropyl pinacol borate, and n-butyllithium is described. Problems associated with implementing a typical aqueous workup and batch process into production due to borolane ate equilibration and protonolysis are presented. To address these issues, a continuous-flow and distillation process was developed which efficiently produced 297 kg of the key propargylation reagent.
- Fandrick, Daniel R.,Roschangar, Frank,Kim, Chunyoung,Hahm, Byoung J.,Cha, Myoung H.,Kim, Hyoun Y.,Yoo, Gyesang,Kim, Taeyun,Reeves, Jonathan T.,Song, Jinhua J.,Tan, Zhulin,Qu, Bo,Haddad, Nizar,Shen, Sherry,Grinberg, Nelu,Lee, Heewon,Yee, Nathan,Senanayake, Chris H.
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supporting information; scheme or table
p. 1131 - 1140
(2012/08/13)
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- Regioselective allene synthesis and propargylations with propargyl diethanolamine boronates
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"Chemical Equation Presented" The utility of propargyl diethanolamine boronates as reagents for the preparation of allenes and homopropargylic alcohols is presented. Protonolysis with TFA and electrophilic substitution with N-halosuccinimides proceeded wi
- Fandrick, Daniel R.,Reeves, Jonathan T.,Tan, Zhulin,Lee, Heewon,Song, Jinhua J.,Yee, Nathan K.,Senanayake, Chris H.
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scheme or table
p. 5458 - 5461
(2010/03/01)
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- Unique σ-bond metathesis of silylalkynes promoted by an ansa-dimethylsilyl and oxo-bridged uranium metallocene
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The tetrachloride salt of uranium reacts with 1 equiv of the lithium ligand Li2[(C5Me4)2SiMe2] in DME to form the complex [η5-(C5Me4)2SiMe2]UCl2·2LiCl·2DME (1), which undergoes a rapid hydrolysis in toluene to yield the dimeric bridged monochloride, monooxide complex [{[η5-(C5Me4)2SiMe2]UCl}2(μ-O)(μ-Cl)?Li?1/2DME]2 (2). Metathesis of 2 with BuLi in DME gives the mono-bridged dibutyl complex {[η5-(C5Me4)2SiMe2]UBu}2(μ-O) (3). Complex 2 was characterized by solid-state X-ray analysis. Complex 3 was found to be an active catalyst for the disproportionation metathesis of TMSC≡CH (TMS = SiMe3) and the cross-metathesis of TMSC≡CH or TMSC≡CTMS with various terminal alkynes. The metathesis of TMSC≡CH gives TMSC≡CTMS and HC≡CH, whereas the cross-metathesis of TMSC≡CH or TMSC≡CTMS with terminal alkynes (RC≡CH) yields TMSC≡CTMS, TMSC≡CR, and HC≡CH. In addition, TMSC≡CCH3 also was found to react with tBuC≡CH, yielding TMSC≡CBut and CH3C≡CH. A plausible mechanism for the catalytic process is presented. Copyright
- Wang, Jiaxi,Gurevich, Ylia,Botoshansky, Mark,Eisen, Moris S.
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p. 9350 - 9351
(2007/10/03)
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- Trimethylsilylated 1,4-Diborinanes and 1,3-Diborolanes - Formation, Isomer Separation, and Characterisation
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Me3SiCCH (A) reacts with excess (Et2BH)2 via the compounds 1, 1' and 2, 2' to yield a mixture of four regio- and stereoisomeric 1,4-diethyl-2,5(6)-bis(trimethylsilyl)-1,4-diborinanes (3a-d) and minor amounts of 1,3-diethyl-2-methyl-trans-2,5-bis(trimethylsilyl)-1,3-diborolane(4a).The 2,5-ee-(Me3Si)2 compound 3d is isolated as the adduct 3d(Pic)2 (X-ray structure analysis), from which pure 3d is obtained with Et2O-BF3. 3d and Me3P form equilibria of the 1:1 and 1:2 addition compounds 3d(Me3P)n (n = 1,2) at room temperature.Me3SiCCMe (B) reacts with (Et2BH)2 via 5 to give 6 - 10, and Me3SiCCSiMe3 (C) reacts with (Et2BH)2 to form the ring compounds 12 and 13 via the presumably threo/erythro mixture of 11a and b. - Key Words: Hydroboration of 1-alkinylsilanes / Ethyldiboranes(6) / Alkyl substituent exchanges, >BH-borane-catalysed / 1,4-Diborinanes, trimethylsilyl-substituted, isomers of / Lewisbase - 1,4-Diborinanes
- Koester, Roland,Seidel, Guenter,Lutz, Frank,Krueger, Carl,Kehr, Gerald,Wrackmeyer, Bernd
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p. 813 - 820
(2007/10/02)
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- A new route to α,β-unsaturated aldehydes using the condensation of trimethylsilyl β-trimethylsilyl enol ethers with aldehydes
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β-Trimethylsilyl enol ethers 1 (Z) obtained from β-bromoenolethers 2 were condensed with aliphatic and aromatic aldehydes in the presence of a catalytic quantity of trimethylsilyl triflate leading to ethylenic aldehydes 3 (E) with good yields (79-90%).
- Duhamel, Lucette
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p. 7745 - 7748
(2007/10/02)
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- Preparation of metallated and substituted alkynes
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A process is provided for making metallated and substituted alkynes from feedstocks which include alkadienes containing allenic unsaturation or such alkadienes in a mixture with alkynes having either internal or terminal unsaturation, such as a mixture of propadiene and propyne. This reaction involves an initial step in which the allenic hydrocarbon and any internal alkyne is isomerized and simultaneously the resultant terminal alkynes are metallated with an alkali metal. The reaction is carried out at relatively low temperatures in a suitable inert solvent such as diethylether. When metallation is complete the reaction mixture can be contacted directly with any suitable electrophile, such as a halo silane, for example, chlorotrimethylsilane, and the alkali metal on the terminal alkyne is replaced with the desired substituent. The products thus formed are useful as monomers for preparing polymers having a variety of properties, for example, as asymmetric membranes for gas separation.
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- The Synthesis and Molecular Structure of Tetra(isopropyl)silane
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Tetra(isopropyl)silane has been prepared using literature methods, with the individual steps improved by changes in some of the experimental conditions.The key reagent 2-lithiopropene, which can now be obtained in good yields from 1-methacrylic acid via 1,2-dibromo-1-methylpropionic acid and 2-bromopropene by treatment of the latter with ultrasound-activated lithium metal, was shown to contain mono- and dilithiopropyne.The reaction with chlorotrimethylsilane led to the corresponding silylated derivatives, while with silicon tetrachloride tetra(isopropenyl)silane was obtained, which after purification is easily converted into the title compound by catalytic hydrogenation. - The gas phase molecular structure of 4Si has been determined by electron diffraction.The parameters could be successfully refined for a model of S4 symmetry.Bond distances Si-C, C-C, and C-H as well as bond angles Si-C-C and C-C-H show the steric compression of the four isopropyl substituents.Steric strain is minimized by twists of the methyl groups and the isopropyl groups away from the fully staggered conformations, but also by an increase of two of the C-Si-C angles as compared to the remaining four, which are decreased relative to the tetrahedral standard.The structure differs strongly (mainly in the twist angles) from that of the isoelectronic tetra(isopropyl)phosphonium cation in 4P(1+)(1-), but is very similar to those of tetra(cyclohexyl)silane and of tri(isopropyl)phosphonium isopropylide, where the pyramidal configuration of the ylidic carbon atoms leads to a pseudo homoleptic array of the substituents at phosphorus. - Key Words: Conformational analysis / Electron diffraction / Organosilanes / Silane, tetra(isopropyl)-
- Anderson, David G.,Rankin, David W. H.,Robertson, Heather E.,Frazao, Carlos M. F.,Schmidbaur, Hubert
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p. 2211 - 2218
(2007/10/02)
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- Oxygen permeable polymeric materials
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A polymer represented by the general formula STR1 where m is the average degree of polymerization of the polymer, y is an integer from 1 to 3, x is an integer from 1 to 10, A denotes a halogen atom and R denotes an alkyl radical with 1 to 6 carbon atoms.
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- Interactions of Thiol-Containing Androgens with Human Placental Aromatase
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A series of thiol androgens were synthesized and investigated to characterize structural features important for the inhibition of aromatase.Analogues of androstenedione with thiol groups in either the 2α-, 10β-, or 19-positions caused time-dependent inhibition of human placental aromatase.When their KI and kcat values were compared with those of 4-hydroxyandrost-4-ene-3,17-dione (4-OHa) and 10-β-propargylestr-4-ene-3,17-dione (PED), the thiol androgen 10β-mercaptoestr-4-ene-3,17-dione (10β-SHnorA) proved to be the most potent suicide substrate.However, 19-merc aptoandrost-4-ene-3,17-dione (19-SHA) was the best all-around inhibitor.All compounds except 19-SHA exhibited normal type I P-450 difference spectra with partially purified/solubilized, human placental aromatase.The KS values for the series of compounds compared qualitatively to the KI values determined from the time and concentration-dependent inhibition experiments. 19-SHA induced split Soret peaks at 380 and 474 nm, which suggested binding of the 19-thiolate directly to the ferric iron of aromatase.This binding could be displaced by aminoglutethimide but not by androstenedione.The inhibitory activity of 19-SHA may be explained by two independent mechanisms: (1) suicide inactivation of aromatase in the ferrous state; and (2) a direct "hyper-type II" binding to the remaining portion of the cytochrome in the ferric state.A free thiol group was necessary for the suicide inhibitory activity of 19-SHA; time-dependent inactivation of aromatase by 19-(acetylthio)androst-4-ene-3,17-dione (19-SAcA) and 19-xanthogenylandrost-4-ene-3,17-dione (19-XanA) could be prevented if the microsomes were preincubated with a carboxyesterase inhibitor.Aromatase previously inactivated by either thiol androgens, 4-OHA, or PED could not be reactivated after incubation with the disulfide reducing agent dithiothreitol, which suggests that a disulfide bond may not be involved in aromatase inactivation by these inhibitors.
- Bednarski, Patrick J.,Nelson, Sidney D.
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p. 203 - 213
(2007/10/02)
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- Sulfone reagents in organic synthesis. VI. Sulfonyl- and silyl-substituted hydrocarbons as versatile carbanion precursors in organic synthesis
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The basic organometallic chemistry of β-silyl-substituted acetylenic, vinylic and alkyl sulfones has been investigated, with attention being given to metallation, carbometallation and the chemical reduction of carbon-carbon unsaturation. 2-Trimethylsilylvinyl and 2-trimethylsilylalkyl sulfones underwent smooth and stereoselective lithiation with RLi on the carbon α to the sulfonyl group. Carbometallation of vinyl sulfones could be achieved with RMgX or LiCuR2, but acetylenic sulfones carbometallated smoothly only with LiCuR2; with RMgX or RLi, these acetylenes underwent alkyldesulfonylation. The utility in synthesis of these metallo derivatives of sulfonyl-silyl-hydrocarbons is discussed and their value in elaborating carbon skeletons is illustrated for the preparation of alkenes, allenes, carbocycles and stereo-defined vinyl sulfones.
- Eisch, John J.,Behrooz, Mohammad,Dua, Suresh K.
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p. 121 - 136
(2007/10/02)
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- THE STEREOCHEMISTRY OF ORGANOMETALLIC COMPOUNDS. XXXVI. REGIO- AND STEREO-CHEMICAL CONTROL IN THE NICKEL-CATALYSED HYDROCYANATION OF SILYLALKYNES
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The regioselectivity of hydrocyanation of silylalkynes can be controlled by varying the size of the groups attached to silicon leading, for example, to efficient preparations of E-3-trialkylsilyl-2-alkyl-2-alkenenitriles.High yields of the silylalkene nitriles can be obtained by using either acetone cyanohydrin or hydrogen cyanide as reagents.
- Fitzmaurice, Neil J.,Jackson, W. Roy,Perlmutter, Patrick
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p. 375 - 382
(2007/10/02)
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- Regio- and Stereocontrolled Synthesis of Allenic and Acetylenic Derivatives. Organotitanium and Boron Reagents
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The propargyltitanium reagents derived from 1-alkylpropyne condensed with aldehydes to give α-allenyl alcohol regioselectively, while the allenyltitanium reagents generated from 1-alkyl-1-butyne derivatives gave threo-β-acetylenic alcohols with high regio- and stereoselectivities.The course of the reaction was determined by the substitution pattern of starting alkynes.The similar reactions of metallated 1,3-bis(trialkylsilyl)propyne or (trialkylsilyl)acetonitrile with aldehydes were also investigated.
- Furuta, Kyoji,Ishiguro, Masaharu,Haruta, Ryuichi,Ikeda, Nobuo,Yamamoto, Hisashi
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p. 2768 - 2776
(2007/10/02)
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- Vinyl Cations, 35. Mechanisms of Formation of Vinyl Triflates on Treatment of Ketones with Trifluoromethanesulfonic Anhydride
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Alkynones (5) are treated with trifluoromethanesulfonic anhydride in the presence of various bases to give 1-(1-alkynyl)vinyl triflates (6).The mechanisms of formation of vinyl triflates are discussed in detail.
- Hanack, Michael,Hassdenteufel, Juergen R.
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p. 764 - 771
(2007/10/02)
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- Gas-Phase Reactions of Anions with Substituted Silanes
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The gas-phase reactions of fluoride, amide, hydroxide, and methoxide ions with a variety of substituted silanes have been studied by the flowing afterglow technique.Fluoride reacts readily with trimethylsilyl derivatives to displace benzyl, alkenyl, and alkynyl anions.These reactions have also been used to generate specific structural isomers (CH3CC- and CH2C=C=CH-).Anions more basic than phenide ion cannot be produced in this manner, and their parent trimethylsilanes interact with fluoride by more complex mechanisms.Amide, hydroxide, and methoxide ions react with substituted trimethylsilanes by both displacement and proton abstraction whenever an acidic hydrogen is present; in the absence of displaceable groups and acidic hydrogen, the reactions of amide, hydroxide, and methoxide parallel those of fluoride ion.
- DePuy, C. H.,Bierbaum, Veronica M.,Flippin, L. A.,Grabowski, Josef J.,King, Gary K.,et al.
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p. 5012 - 5015
(2007/10/02)
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