- Silylation of Alcohols, Phenols, and Silanols with Alkynylsilanes – an Efficient Route to Silyl Ethers and Unsymmetrical Siloxanes
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The formation of several silyl ethers (alkoxysilanes, R3Si-OR') and unsymmetrical siloxanes (R3Si-O-SiR'3) can be catalyzed by the commercially available potassium bis(trimethylsilyl)amide (KHMDS). The reaction proceeds via direct dealkynative coupling between various alcohols or silanols and alkynylsilanes, with a simultaneous formation of gaseous acetylene as the sole by-product. The dehydrogenative and dealkenative coupling of alcohols or silanols are well-investigated, whilst the utilization of alkynylsilanes as silylating agents has never been comprehensively studied in this context. Overall, the presented system allows the synthesis of various attractive organosilicon compounds under mild conditions, making this approach an atom-efficient, environmentally benign, and sustainable alternative to existing synthetic solutions.
- Kuciński, Krzysztof,Stachowiak, Hanna,Hreczycho, Grzegorz
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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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- Mechanistic Studies and Expansion of the Substrate Scope of Direct Enantioselective Alkynylation of α-Ketiminoesters Catalyzed by Adaptable (Phebox)Rhodium(III) Complexes
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Mechanistic studies and expansion of the substrate scope of direct enantioselective alkynylation of α-ketiminoesters catalyzed by adaptable (phebox)rhodium(III) complexes are described. The mechanistic studies revealed that less acidic alkyne rather than more acidic acetic acid acted as a proton source in the catalytic cycle, and the generation of more active (acetato-κ2O,O′)(alkynyl)(phebox)rhodium(III) complexes from the starting (diacetato)rhodium(III) complexes limited the overall reactivity of the reaction. These findings, as well as facile exchange of the alkynyl ligand on the (alkynyl)rhodium(III) complexes led us to use (acetato-κ2O,O′)(trimethylsilylethynyl)(phebox)rhodium(III) complexes as a general precatalyst for various (alkynyl)rhodium(III) complexes. Use of the (trimethylsilylethynyl)rhodium(III) complexes as precatalysts enhanced the catalytic performance of the reactions with an α-ketiminoester derived from ethyl trifluoropyruvate at a catalyst loading as low as 0.5 mol % and expanded the substrate scope to unprecedented α-ketiminophosphonate and cyclic N-sulfonyl α-ketiminoesters.
- Morisaki, Kazuhiro,Sawa, Masanao,Yonesaki, Ryohei,Morimoto, Hiroyuki,Mashima, Kazushi,Ohshima, Takashi
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- Lewis base mediated β-elimination and lewis acid mediated insertion reactions of disilazido zirconium compounds
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The reactivity of a series of disilazido zirconocene complexes is dominated by the migration of anionic groups (hydrogen, alkyl, halide, OTf) between the zirconium and silicon centers. The direction of these migrations is controlled by the addition of two-electron donors (Lewis bases) or two-electron acceptors (Lewis acids). The cationic nonclassical [Cp2ZrN(SiHMe 2)2]+ ([2]+) is prepared from Cp2Zr{N(SiHMe2)2}H (1) and B(C 6F5)3 or [Ph3C][B(C 6F5)4], while reactions of B(C 6F5)3 and Cp2Zr{N(SiHMe 2)2}R (R = Me (3), Et (5), n-C3H7 (7), CH? -CHSiMe3 (9)) provide a mixture of [2]+ and [Cp2ZrN(SiHMe2)(SiRMe2)]+. The latter products are formed through B(C6F5)3 abstraction of a β-H and R group migration from Zr to the β-Si center. Related β-hydrogen abstraction and X group migration reactions are observed for Cp2Zr{N(SiHMe2)2}X (X = OTf (11), Cl (13), OMe (15), O-i-C3H7 (16)). Alternatively, addition of DMAP (DMAP = 4-(dimethylamino)pyridine) to [2]+ results in coordination to a Si center and hydrogen migration to zirconium, giving the cationic complex [Cp2Zr{N(SiHMe2)(SiMe2DMAP)}H] + ([19]+). Related hydrogen migration occurs from [Cp 2ZrN(SiHMe2)(SiMe2OCHMe2)] + ([18]+) to give [Cp2Zr{N(SiMe 2DMAP)(SiMe2OCHMe2)}H]+ ([22] +), whereas X group migration is observed upon addition of DMAP to [Cp2ZrN(SiHMe2)(SiMe2X)]+ (X = OTf ([12]+), Cl ([14]+)) to give [Cp 2Zr{N(SiHMe2)(SiMe2DMAP)}X]+ (X = OTf ([26]+), Cl ([20]+)). The species involved in these transformations are described by resonance structures that suggest β-elimination. Notably, such pathways are previously unknown in early metal amide chemistry. Finally, these migrations facilitate direct Si-H addition to carbonyls, which is proposed to occur through a pathway that previously had been reserved for later transition metal compounds.
- Yan, Kaking,Duchimaza Heredia, Juan J.,Ellern, Arkady,Gordon, Mark S.,Sadow, Aaron D.
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- A new synthetic route to donor-acceptor porphyrins
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Some new donor-acceptor porphyrins have been prepared based on a metallated bis(ethynyl) porphyrin core. 4-(Dimethylamino)phenyl was used as the donor group and 4-nitrophenyl, 4-cyanophenyl and 5-nitrothiazoyl as the acceptor groups. Dipyrrylmethane was used for large scale porphyrin ring synthesis because the absence of methylene substituents reduces the difficulty of substituent scrambling that occurs during porphyrin synthesis.
- Plater, M.John,Aiken, Stuart,Bourhill, Grant
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- Simple procedures for ethynylmagnesium bromide, ethynyltrialkylsilanes and ethynyltrialkylstannanes
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1 Molar solutions of ethynylmagnesium bromide in tetrahydrofuran can be successfully prepared by introducing acetylene into a cooled solution of ethylmagnesium bromide. Subsequent reaction with trialkylsilyl or trialkylstannyl chloride gives the expected ethynyl derivatives in excellent yields.
- Brandsma,Verkruijsse
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- Preparation of a Diethynyl Hypervalent Silicon Monomer by Coordination-selective Cleavage: Structure and Polymerization to give Novel Polycarbosilanes containing Main-chain Hexacoordinate Silicon
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The hexacoordinate monomer R2Si(CCH)2 , formed from R2Si(CCSiMe3)2 by coordination-selective cleavage of the trimethylsilyl-acetylene bonds in the presence of Bun4NF, undergoes palladium-catalysed cross-coupling polymerization with dihaloarenes to afford novel polycarbosilanes n (Ar = 1,4-phenylene, 4,4'-biphenylene, 9,10-anthrylene) containing hexacoordinate silicon.
- Boyer-Elma, Karine,Carre, Francis H.,Corriu, Robert J.-P.,Douglas, William E.
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- Trimethylsilylacetylene synthesis process
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The invention discloses a process route for synthesizing trimethylsilylacetylene, which comprises the following steps of: generating trimethylchlorosilylethylene by taking ethylene bromide and trimethylchlorosilane as initial raw materials through a Grignard method, and forming 1-bromo trimethylchlorosilylethylene under the action of alkali through a bromination reagent; and removing monomolecularhydrogen bromide under the action of strong alkali to generate trimethylsilylacetylene. Compared with the traditional process, the process route has the advantages that the use of gas acetylene is avoided, the risk is reduced, the safety is improved, the used raw materials are easily available, the operation is easy, the safety and the environmental protection are realized, and the industrial production can be realized.
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Paragraph 0024; 0025
(2021/01/11)
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- Three-coordinate copper(II) alkynyl complex in C-C bond formation: The sesquicentennial of the glaser coupling
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Copper(II) alkynyl species are proposed as key intermediates in numerous Cu-catalyzed C-C coupling reactions. Supported by a β-diketiminate ligand, the three-coordinate copper(II) alkynyl [CuII]-C≡CAr (Ar = 2,6-Cl2C6H3) forms upon reaction of the alkyne H-C≡CAr with the copper(II) tertbutoxide complex [CuII]-OtBu. In solution, this [CuII]-C≡CAr species cleanly transforms to the Glaser coupling product ArC≡C-C≡CAr and [CuI](solvent). Addition of nucleophiles R′C≡C-Li (R′ = aryl, silyl) and Ph-Li to [CuII]-C≡CAr affords the corresponding Csp-Csp and Csp-Csp2 coupled products RC≡C-C≡CAr and Ph-C≡CAr with concomitant generation of [CuI](solvent) and {[CuI]-C≡CAr}-, respectively. Supported by density functional theory (DFT) calculations, redox disproportionation forms [CuIII](C≡CAr)(R) species that reductively eliminate R-C≡CAr products. [CuII]-C≡CAr also captures the trityl radical Ph3C· to give Ph3C-C≡CAr. Radical capture represents the key Csp-Csp3 bond-forming step in the copper-catalyzed C-H functionalization of benzylic substrates R-H with alkynes H-C≡CR′ (R′ = (hetero)aryl, silyl) that provide Csp-Csp3 coupled products R-C≡CR via radical relay with tBuOOtBu as oxidant.
- Warren, Timothy H.,Bakhoda, Abolghasem,Okoromoba, Otome E.,Greene, Christine,Boroujeni, Mahdi Raghibi,Bertke, Jeffery A.
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supporting information
p. 18483 - 18490
(2020/11/27)
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- Preparation technology of trimethylsilylacetylene
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Trimethylsilylacetylene is an important chemical product. The technological process comprises steps as follows: (1) preparation of an n-butyl magnesium chloride Grignard reagent; (2) preparation of a unilateral ethynylmagnesium chloride Grignard reagent; (3) preparation of trimethylsilylacetylene; (4) distillation; (5) washing; (6) removal of calcium chloride by suction filtration; (7) atmospheric distillation.
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Paragraph 0001; 0002
(2017/07/19)
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- Lanthanide-Catalyzed Reversible Alkynyl Exchange by Carbon–Carbon Single-Bond Cleavage Assisted by a Secondary Amino Group
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Lanthanide-catalyzed alkynyl exchange through C?C single-bond cleavage assisted by a secondary amino group is reported. A lanthanide amido complex is proposed as a key intermediate, which undergoes unprecedented reversible β-alkynyl elimination followed by alkynyl exchange and imine reinsertion. The in situ homo- and cross-dimerization of the liberated alkyne can serve as an additional driving force to shift the metathesis equilibrium to completion. This reaction is formally complementary to conventional alkyne metathesis and allows the selective transformation of internal propargylamines into those bearing different substituents on the alkyne terminus in moderate to excellent yields under operationally simple reaction conditions.
- Shao, Yinlin,Zhang, Fangjun,Zhang, Jie,Zhou, Xigeng
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supporting information
p. 11485 - 11489
(2016/10/24)
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- C-substituted, 1H-azoles for amphoteric, solvent-less proton conductivity
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Disclosed herein are the compounds shown below. Also disclosed are methods of making the compounds. R1=—O—; R2=any alkyl chain; R3=—CH3, —CN, —COOCH3, -tetrazole, -imidazole, or -triazole; R4=—H or —R5; R5=—H, -halogen, —C≡CH, or —C≡C—; n is a positive integer; and m is a positive integer.
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- Tandem Claisen Rearrangement/6-endo Cyclization Approach to Allylated and Prenylated Chromones
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Allyl, dimethylallyl and prenyl ethers derived from o-acylphenols reacted upon microwave irradiation to form C-allylated or -prenylated chromone derivatives, depending on the substitution pattern of the arene and the allyl substituent. The reaction proceeds through a tandem Claisen rearrangement and 6-endo-trig or 6-endo-dig cyclization sequence. For prenyl ethers, the tandem sequence can be extended by a Cope rearrangement to furnish 6-prenylchromones. The method is potentially useful for the synthesis of natural products and drugs.
- Schmidt, Bernd,Riemer, Martin,Schilde, Uwe
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supporting information
p. 7602 - 7611
(2016/01/25)
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- C-SUBSTITUTED, 1H-AZOLES FOR AMPHOTERIC, SOLVENT-LESS PROTON CONDUCTIVITY
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Disclosed herein are the compounds shown below. Also disclosed are methods of making the compounds. R1=—O—; R2=any alkyl chain; R3=—CH3, —CN, —COOCH3, -tetrazole, -imidazole, or -triazole; R4=—H or —R5; R5=—H, -halogen, —C≡CH, or —C≡C—; n is a positive integer; and m is a positive integer.
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(2014/02/16)
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- 1,4-OXAZEPINES AS BACE1 AND/OR BACE2 INHIBITORS
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The present invention relates to 1,4 Oxazepines of formula I having BACE1 and/or BACE2 inhibitory activity, their manufacture, pharmaceutical compositions containing them and their use as therapeutically active substances. The active compounds of the present invention are useful in the therapeutic and/or prophylactic treatment of e.g. Alzheimer's disease and type 2 diabetes.
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Page/Page column 47
(2012/10/08)
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- The behaviors of metal acetylides with dinitrogen tetroxide
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Lithium phenylacetylide (1a) and N2O4 (2) at - 78° yield diphenylbutadiyne (6a) by oxidative coupling, phenylacetylene (7a) by oxidation and then solvent H-abstraction, and benzoyl cyanide (8) by dimerizative-rearrangement of nitroso(phenyl)acetylene (23). Nitro(phenyl)acetylene (3, R = Ph) is not obtained. Benzonitrile (9), a further product, possibly results from hydrolytic decomposition of nitroso(phenyl)ketene (27) generated from phenylacetylenyl nitrite (26). Phenylacetylene (7a) and 2 give, along with (E)- and (Z)-1,2-dinitrostyrenes (34 and 35, resp.), 3-benzoyl-5-phenylisoxazole (10), presumably as formed by cycloaddition of benzoyl nitrile oxide (40) to 7a. Further, 2 reacts with other lithium acetylides (1b-1e), and with sodium, magnesium, zinc, copper, and copper lithium phenylacetylides, 1f-1l, to yield diacetylenes 6a-6c and monoacetylenes 7a-7c. Conversions of metallo acetylide aggregates to diacetylenes are proposed to involve generation and addition reactions of metallo acetylide radical cationic intermediates in cage, further oxidation, and total loss of metal ion. Loss of metal ions from metallo acetylide radical cations and H-abstraction by non-caged acetylenyl radicals will give terminal acetylenes. The principal reactions (75-100%) of heavy metal acetylides phenyl(trimethylstannyl)acetylene (44) and bis(phenylacetylenyl)mercury (47) with 2 are directed nitrosative additions (NO+) and loss of metal ions to give nitroso(phenyl)ketene (27), which converts to benzoyl cyanide (8).
- Woltermann, Christopher J.,Shechter, Harold
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p. 354 - 369
(2007/10/03)
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- METHOD FOR THE PRODUCTION OF ACETYLENE ALCOHOLS
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The invention relates to a method for producing acetylene alcohols of general formula (I), wherein R1, R2 can independently be identical or different and represent optionally substituted hydrogen, an optionally substituted saturated, monounsaturated or polyunsaturated C1-C30 alkyl radical, aryl radical, cycloalkylalkyl radical, or cycloalkyl radical, or a group of general formula (II), wherein R3, R4 can independently be identical or different and represent optionally substituted hydrogen or an optionally substituted saturated, monounsaturated, or polyunsaturated C1-C30 alkyl radical, aryl radical, cycloalkylalkyl radical, or cycloalkyl radical while the dashed line can represent an additional double bond. Said acetylene alcohols are produced by monoethynylating a ketone of general formula R1-CO-R2 by (a) reacting lithium with a C1-C10 alkyl halide, (b) introducing acetylene gas, and (c) adding the ketone.
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(2008/06/13)
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- Process for preparing bisallylboranes and nonaromatic boronic acids
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A process for preparing bisallylboranes of the formula (I) by reacting a diene with sodium borohydride in the presence of an oxidant in an inert solvent, with the borane generated in situ reacting selectively with the diene to form the bis(allyl)borane of the formula (I) and the substituents R1 to R6 having the following meanings: R1-R6 are H, aryl or substituted or unsubstituted C1-C4-alkyl or two radicals R may be closed to form a cyclic system. As oxidant, it is possible to use, for example, alkyl halides or dialkyl sulfates. In a particularly preferred embodiment, the diene used is 2,5-dimethylhexa-2,4-diene (R1, R2, R5, R6=methyl, R3, R4=H).
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- Synthesis and characterization of coordinatively unsaturated alkynyl- and aryl-cobalt complexes with 15 valence electrons, TpiPr2Co-R, bearing the hydrotris(3,5-diisopropylpyrazolyl)borato ligand (TpiPr2)
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Coordinatively unsaturated 15e alkynyl- (TpiPr2Co-C≡C-R) and aryl-cobalt complexes (TpiPr2Co-aryl) bearing the hydrotris(3,5-diisopropylpyrazolyl)borato ligand (TpiPr2) are prepared by dehydrative condensation of the hydroxo complex [TpiPr2Co(μ-OH)2]2 with 1-alkyne and arylation of the chloro complex TpiPr2Co-Cl with Grignard reagents, respectively. Spectroscopic and crystallographic analyses reveal the apparent C3-symmetrical tetrahedral structures with high-spin electronic configuration (S = 3/2), which should result from the property of the TpiPr2 ligand as a tetrahedral enforcer. The TpiPr2Co and hydrocarbyl fragments, are connected dominantly through σ-bonding interaction, and π-interaction including back-donation is not significant as revealed by EHMO calculations. The Co-C bonds are so polarized as to be readily protonated even by moisture to give the corresponding hydrocarbons, but the reactivity toward unsaturated hydrocarbons turns out to be sluggish. TpiPr2Co-C≡C-COOMe is found to catalyze a rare example of specific linear trimerization of methyl propiolate to give (E,E)-MeOOC(H)C=CH-CH=C(COOMe)-C≡C-COOMe.
- Yoshimitsu, Shin-Ichi,Hikichi, Shiro,Akita, Munetaka
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p. 3762 - 3773
(2008/10/08)
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- Preparation of preparing substituted indanones
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a process for the preparation of indanones of the formula II from, indanones of the formula I or of indanones of the formula IIa from indanones of the formula Ia comprises reacting an indanone of the formula I or Ia with a coupling component.
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- Silylenes of the elemental composition C4H2Si: Generation and matrix-spectroscopic identification
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Flash pyrolysis of 1,1-diethynyl-2,2,2-trimethyldisilane (16) and triethynylsilane (18) led to the formation of two silylenes of the elemental composition C4H2Si, namely diethynylsilylene (10) and ethynylsilacyclopropenylidene (7), which were isolated in an argon matrix at 10 K. Both compounds could be photoconverted into another isomer, butadiynylsilylene (9). The identification of these reactive intermediates is based on the comparison between the experimental and calculated IR spectra for the parent compounds as well as for their dideuterated and fully 13C-labeled isotopomers.
- Maier, Guenther,Reisenauer, Hans Peter,Meudt, Andreas
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p. 1285 - 1290
(2007/10/03)
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- Enantioselective catalysis 107: new optically active deltacyclenes as building blocks for the synthesis of expanded phosphanes
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The cobalt-catalyzed homo Diels-Alder reaction of norbornadiene and terminal acetylenes yields chiral deltacyclenes.We tried to extend the scope of this reaction to acetylenes containing a heteroatom (i) in the propargylic position, (ii) in the ortho position of phenylacetylene or (iii) directly bonded to the triple bond.The synthesis of nine new substituted deltacyclenes with cobalt cytalysts derived from CoI2 and zinc powder or Co(acac)3 and Et2AlCl is described.Using Norphos as a cocatalyst, the products are obtained in high enantiomeric excess. - Keywords: enantioselective homogeneous catalysis; homo Diels-Alder reaction; deltacyclene; terminal acetylene
- Brunner, Henri,Reimer, Alfred
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p. 307 - 314
(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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- PLA2 INHIBITORS AS ANTIINFLAMMATORIES
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This invention relates to novel compounds for treating inflammatory conditions by inhibition of phospholipase A2 activity of the formula (I), compositions comprised of the novel compounds; and methods of treating inflammatory conditions with these composition
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- Mechanism of CH2.+ Transfer from Distonic Ions X-CH2.+ (X=CH2O, CH2CH2) to ?- and n-Electron Bases in the Gas Phase. A Fourier Transform Ion Cyclotron Resonance (FTICR) Study Supplemented by ab initio MO Calculations
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The reactions of acetonitrile, propyne, acetylene, trimethylsilylacetylene, and tetramethylsilane, with distonic ions CH2XCH2.+ are studied in the gas phase using Fourier Transform Ion Cyclotron Resonance (FTICR) mass spectrometry.In line with previous studies, CH2.+ is transferred to the electron lone-pair of the nitrogen atom of CH3CN to generate CH3CN-CH2.+ (4); upon collisional excitation, this ion undergoes competitive losses of H. and CH..While both neutrals originate from the "methylene" unit of 4, detailed studies employing labeledsubstrates and using various types of collision experiments reveal an intriguing dissociation pattern in that the dissociations are preceded by two intramolecular hydrogen migrations giving rise to CH3C(H)=NCH.+ (6) and CH3C=N(H)CH.+ (7).While 6 serves as intermediate en route to loss of H. from the "CH" moiety, 7 is the actual precursor to generate, by loss of CH., protonated acetonitrile, CH3CNH+ (12) (Scheme 5).In addition, 12 is formed by bimolecular proton transfer.In this reaction, translationally excited CX3CN-CY2.+* (X, Y = H, D) transfers X+ to neutral CX3CN to generate CX3CNX+ (Scheme 4).The bimolecular proton transfer as well as the intramolecular isomerizations of 4 to 6 and 7 are subject to very large kinetic isotope effects.In the transfer of CH2.+ to CH3CCH two products are formed .+ (16) and CH2=C=CHCH3.+ (17) presumably via intermediate 18 (Scheme 6)>; the latter is formed by addition of CH2.+ to the less hindered carbon atom of HCCCH3 reflecting the higher stability of the so-formed intermediate compared with addition to C-2.Reactions of 2 and 3 with HCCH do not result in the formation of a detectable CH2.+-transfer product.When using CH2CH2CH2.+ (2) the reaction is prohibited by the endothermicity to generate the initial complex (structurally related to 18).On the other hand, when CH2OCH2.+ (3) is employed, the intermediate of CH2.+ transfer is formed with sufficient energy to split off a hydrogen atom.Preliminary experiments with silicon-containing molecules, like Si(CH3)4 or HCCSi(CH3)3, demonstrate that the favored processes of these neutrals with 2 and 3 are due to charge transfer (in the form of an electron or an anion like CH3- or C2H-) from the silicon-containing molecule to the distonic ions.The experimental results obtained for CH3CN/CH2.+ system are supported by ab initio MO calculations (3-21G/3-21G + ZPVE).
- Rusli, Ridwan D.,Schwarz, Helmut
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p. 535 - 540
(2007/10/02)
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- PALLADIUM-CATALYZED REACTIONS OF TRIALKYLSTANNYL PHENYL SULFIDES WITH ALKENYL BROMIDES. A NEW DIASTEREOSELECTIVE SYNTHESIS OF (E)-1-ALKENYL PHENYL SULFIDES
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The reaction of easily available stereoisomeric mixtures of 1-alkenyl bromides with molar excesses of trialkylstannyl phenyl sulfides takes place readily in the presence of Pd(PPh3)4 to afford diastereoselectively (E)-1-alkenyl phenyl sulfides in excellent yields.
- Carpita, Adriano,Rossi, Renzo,Scamuzzi, Barbara
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p. 2699 - 2702
(2007/10/02)
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- Synthesis and Properties of Some Silylethynylsilane; Molecular Structure of Tetrakis(trimethylsilylethynyl)silane
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Trimethylsilylethine (1) has been prepared from C2H2, sodium and Me3SiCl in anisole.The product can be converted into a Grignard reagent Me3SiCCMgCl using iPrMgCl.This reagent yields the compounds Me3SiCCSiH3, (Me3SiCC)2SiH2, (Me3SiCC)3SiH, and (Me3SiCC)4Si (2-5) when treated with equivalent amounts of H3SiBr, H2SiBr2, HSiCl3, or SiCl4, respectively.The new silanes have been characterized by NMR data.The crystal structure of (Me3SiCC)4Si has been determined by single crystal X-ray diffraction.It shows the expected tetrahedral geometry at the central silicon atom with four linear SiCCSi linkages. - Keywords: Silylethynylsilane, Molecular Structure, Tetrakis(trimethylsilylethynyl)silane
- Schmidbaur, Hubert,Ebenhoech, Jan,Mueller, Gerhard
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- The Synthesis of Some Thiophenophanes and Attempted Cyclisations to Polycyclic Thiophenium Salts
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5,10-Diphenylcyclotrideca-2,4,10,12-tetraene-6,8-diyn-1-one (28), 5,6,7,8-tetrahydrodibenzocyclotridecen-15-one (21), and 13,14,16,17-tetrahydro-5,6,7,8-tetradehydrodibenzocyclotridecen-15-one (40) were synthesized.All attempts to add hydrogen sulphide across the triple bonds of these compounds to give thiophenes failed. 13,14,16,17-Tetrahydro-5,8-epithiodibenzocyclotridecen-15-one (43), from which hydrogen sulphide was removed by DDQ or chloroanil to give the ketone (40), was synthesized via the copper(II) acetate oxidation of 1,5-bis(2-ethynylphenyl)pentan-3-one (36).This ketone was obtained from 2-iodobenzaldehyde which on successive treatment with acetone, and ethynyltrimethylsilane yielded 1,5-bis(2-trimethylsilylethynylphenyl)penta-1,4-dien-3-one (18).Tributyltin hydride reduced the vinyl double bonds only in this ketone, and subsequent hydrolysis gave the ketone (36).Reduction of the cyclic ketone (40) with sodium borohydride gave the alcohol (41), sodium sulphide converted the diyne grouping into a thiophene ring giving the thiophene alcohol (42), and chromic acid now yielded the ketone (43).Attempts to convert this alcohol (42) and ketone (43) into pentacyclic sulphonium salts or related compounds resulted in elimination of oxygen and the formation of olefins.
- Acheson, R. Morrin,Lee, Gary C. M.
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p. 2321 - 2332
(2007/10/02)
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- Action du chlorure de fer(III) sur des acetyleniques substitues par des elements de la colonne IVB. Formation de diynes
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We have studied the behaviour of mono- and diheterosubstituted acetylenies (1,2,3) in the presence of iron(III) chloride in a carbon tetrachloride-toluene medium at 25 deg C. 1: ; 2: ; 3: .The reaction always takes place in heterogeneous phase, the reaction medium being carefully kept free from air and humidity. Compounds of type 1. The reaction rate increases from the carbon compound to the stannyl compound. The germyl and stannyl acetylenics give 2,4-hexadiyne with good yields, respectively 62 and 84percent . Compounds of types 2 and 3. The influence of heterosubstituents on the reaction rate is the same as for compounds 1.For the mixed compound 3b, only one hexadiyne can be obtained with a yield of 90percent, gis(trimethylsilyl)buta-1,3-diyne.In the course of all these reactions, iron(III) is reduced into iron(II). The influence of the metal and its substituents as well as the action of iron chloride on the various conjugated diynes are discussed.A mechanism based on the respective reaction rates is suggested.
- Braun, Jacques,Trung, Bui Khac
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- C-Silylated Hydroxyaldehydes, Hydroxyketones, and Carbohydrates
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The Grignard compound of (trimethylsilyl)methyl chloride (1) adds to the carbonyl group of the aldehydes, ketones, and sugar derivatives 2, 4, 6, 8, 10, 12, and 15 to yield the C-silylated hydroxyaldehydes, -ketones, and carbohydrates 3, 5, 7, 9, 11, 13, 14, and 16. - (Trimethylsilyl)ethylmagnesium bromide (17) gives 2, 4, 6, 23, and 8 the C-(trimethylsilyl)ethynylated hydroxy compounds 18, 19, 21, 22, 24, and 25.
- Birkofer, Leonhard,Wundram, Dieter
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p. 1132 - 1140
(2007/10/02)
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- vic-Iodothiocyanates and Iodoisothiocyanates. Part 4. The Synthesis of 2-Substituted-2-thiazolines
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The reactions of trans-1-iodo-2-isothiocyanatocyclohexane with a number of carbon nucleophiles to form 2-substituted-2-thiazolines are described.Reactions of several vic-iodoisothiocyanates with butil-lithium give products which are dependent on the solvent and/or temperature.
- Cambie, Richard C.,Chambers, David,Rutledge, Peter S.,Woodgate, Paul D.
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