- Gold(I)-Catalyzed Oxidative 1,4-Additions of 3-En-1-ynamide with Nitrones via Carbon- versus Nitrogen-Addition Chemoselectivity
-
This work reports gold-catalyzed 1,4-oxofunctionalizations of 3-en-1-ynamides with nitrones, yielding two distinct E-configured products. We obtained 1,4-oxoarylation products from 3-en-1-ynamides bearing C(4)-electron-donating substituents and 1,4-oxoamination products from those analogues bearing C(4)-aryl substituents. We propose that if vinylgold carbenes are stable, imines undergo a para-arylation on these gold carbenes. If vinylgold carbenes are highly electron-deficient, this N-attack is irreversible to enable 1,4-oxoaminations.
- Tanpure, Sudhakar Dattatray,Kale, Balaji S.,Liu, Rai-Shung
-
p. 1394 - 1399
(2021/02/20)
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- Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand
-
The hydroformylation of terminal arylalkynes and enynes offers a straightforward synthetic route to the valuable (poly)enals. However, the hydroformylation of terminal alkynes has remained a long-standing challenge. Herein, an efficient and selective Rh-catalyzed hydroformylation of terminal arylalkynes and conjugated enynes has been achieved by using a new stable biphosphoramidite ligand with strong π-acceptor capacity, which affords various important E-(poly)enals in good yields with excellent chemo- and regioselectivity at low temperatures and low syngas pressures.
- Zhao, Jiangui,Zheng, Xueli,Tao, Shaokun,Zhu, Yuxin,Yi, Jiwei,Tang, Songbai,Li, Ruixiang,Chen, Hua,Fu, Haiyan,Yuan, Maolin
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p. 6067 - 6072
(2021/08/16)
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- Synthesis of alkynes under dry reaction conditions
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An easy synthetic method was developed under dry reaction conditions for the preparation of terminal alkynes from 1,1-dibromoalkenes and in the presence of succinimide which acts as a nucleophile and proton donor. It was demonstrated with the synthesis of a broad spectrum of terminal alkynes and extended to synthesize internal alkynes under tandem reaction conditions.
- Rao, Maddali L.N.,Shamim Islam, Sk
-
supporting information
(2021/04/19)
-
- Aminium cation-radical catalysed selective hydration of (E)-aryl enynes
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The hydration of carbon-carbon triple bonds is an important and atom economic synthetic transformation. Herein, we report a mild and selective method for the catalytic Markovnikov hydration of (E)-aryl enynes to the corresponding enones, mediated through the bench-stable aminium salt, tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBPA). The chemoselective and diastereoselective method proceeds under neutral metal-free conditions, delivering excellent product yields from terminal and internal alkyne units. The synthesis of biologically important (E)-3-styrylisocoumarins, including a formal synthesis of the natural product achlisocoumarin III, demonstrates the utility of this novel transformation.
- Giel, Marie-Claire,Barrow, Andrew S.,Smedley, Christopher J.,Lewis, William,Moses, John E.
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p. 6991 - 6994
(2021/07/21)
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- Cu-mediated or metal-free alkylation of gem-dibromoalkenes with tertiary, secondary and primary alkyl Grignard reagents
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A novel copper-mediated or transition-metal-free alkylation of gem-dibromoalkenes with tertiary, secondary and primary alkyl Grignard reagents was described. The outcomes of these reactions were found to be highly dependent on the reaction conditions and
- Deng, Yupian,Zhang, Xuxue,Liu, Chuan,Cao, Song
-
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- Iron-Catalyzed Tertiary Alkylation of Terminal Alkynes with 1,3-Diesters via a Functionalized Alkyl Radical
-
Direct oxidative C(sp)?H/C(sp3)?H cross-coupling offers an ideal and environmentally benign protocol for C(sp)?C(sp3) bond formations. As such, reactivity and site-selectivity with respect to C(sp3)?H bond cleavage have remained a persistent challenge. Herein is reported a simple method for iron-catalyzed/silver-mediated tertiary alkylation of terminal alkynes with readily available and versatile 1,3-dicarbonyl compounds. The reaction is suitable for an array of substrates and proceeds in a highly selective manner even employing alkanes containing other tertiary, benzylic, and C(sp3)?H bonds alpha to heteroatoms. Elaboration of the products enables the synthesis of a series of versatile building blocks. Control experiments implicate the in situ generation of a tertiary carbon-centered radical species.
- Tian, Ming-Qing,Shen, Zhen-Yao,Zhao, Xuefei,Walsh, Patrick J.,Hu, Xu-Hong
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p. 9706 - 9711
(2021/03/19)
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- Fischer Carbene Pentannulation with Alkynes Having Adjacent Carbonate or Acyloxy Groups: Synthesis of 3-Substituted 1-Indanones
-
Various aryl Fischer carbenes reacted with alkynes having adjacent acyloxy or carbonate groups to regioselectively deliver 3-substituted 1-indanones. The acyloxy or carbonate group probably coordinates with the Cr metal to give a tetra-coordinated chromium complex forming a six-membered ring that retards CO insertion for ketene formation, which is required for benzannulation. Alternatively, the ortho position aryl ring attack results in pentannulation, providing regioselectively 3-substituted 1-indanones. The method is extended to the synthesis of the core structure of 3-epi-mutisianthol.
- Bhattacharyya, Shubhankar,Chavan, Vijay P.,Fernandes, Rodney A.,Gholap, Sachin P.,Saiyed, Akeel S.
-
p. 3438 - 3443
(2020/04/20)
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- Towards More Photostable, Brighter, and Less Phototoxic Chromophores: Synthesis and Properties of Porphyrins Functionalized with Cyclooctatetraene
-
Free base and zinc porphyrins functionalized with cyclooctatetraene (COT), a molecule known as a good triplet-state quencher, have been obtained and characterized in detail by structural, spectral, and photophysical techniques. Substitution with COT leads to a dramatic decrease of the intrinsic lifetime of the porphyrin triplet. As a result, photostability in oxygen-free solution increases by two to three orders of magnitude. In non-degassed solutions, improvement of photostability is about tenfold for zinc porphyrins, but the free bases become less photostable. Similar quantum yields of photodegradation in free base and zinc porphyrins containing the COT moiety indicate a common mechanism of photochemical decomposition. The new porphyrins are expected to be much less phototoxic, since the quantum yield of singlet oxygen formation strongly decreases because of the shorter triplet lifetime. The reduction of triplet lifetime should also enhance the brightness and reduce blinking in porphyrin chromophores emitting in single-molecule regime, since the duration of dark OFF states will be shorter.
- Ostapko, Jakub,Gorski, Aleksander,Buczyńska, Joanna,Golec, Barbara,Nawara, Krzysztof,Kharchenko, Anastasiia,Listkowski, Arkadiusz,Ceborska, Magdalena,Pietrzak, Mariusz,Waluk, Jacek
-
supporting information
p. 16666 - 16675
(2020/10/06)
-
- Iron(II)-Based Metalloradical Activation: Switch from Traditional Click Chemistry to Denitrogenative Annulation
-
A unique concept for the intermolecular denitrogenative annulation of 1,2,3,4-tetrazoles and alkynes was discovered by using a catalytic amount of Fe(TPP)Cl and Zn dust. The reaction precludes the traditional, more favored click reaction between an organic azide and alkynes, and instead proceeds by an unprecedented metalloradical activation. The method is anticipated to advance access to the construction of important basic nitrogen heterocycles, which will in turn enable discoveries of new drug candidates.
- Roy, Satyajit,Khatua, Hillol,Das, Sandip Kumar,Chattopadhyay, Buddhadeb
-
supporting information
p. 11439 - 11443
(2019/07/17)
-
- DBU-Mediated Synthesis of Aryl Acetylenes or 1-Bromoethynylarenes from Aldehydes
-
Two well known synthetic organic reactions Ramirez olefination and Corey-fuchs reactions are integrated in one-pot sequential manner for the synthesis of arylacetylenes and 1,3-enynes starting directly from commercially available aldehydes. The bicyclic amidine 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) along with additive NaOH not only exclusively afforded the terminal alkynes directly from the aldehydes, but also enhanced the reaction rate. The dynamic nature of DBU also facilitated the isolation of 1-bromoalkynes intermediate products. Selection of additive from NaOH and H2O served as a switch for the synthesis of terminal alkyne and 1-bromoalkynes, respectively. (Figure presented.).
- Thummala, Yadagiri,Karunakar, Galla V.,Doddi, Venkata Ramana
-
supporting information
p. 611 - 616
(2019/01/04)
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- One-Pot Conversion of Aldehydes and Ketones into 1-Substituted and 1,4-Disubstituted 1,3-Enynes
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Sequential treatment of 2,3-dichloropropene with magnesium and n -BuLi generates the operational equivalent of 1,3-dilithiopropyne, which upon treatment with aldehydes or ketones, produces the corresponding alkoxy lithium acetylide intermediates. Reaction of this alkoxide with tosyl chloride, and t -BuLi produces 1-substituted, or 1,1-disubstituted 1,3-enynes in a one-pot reaction. When this lithium acetylide intermediates, obtained by this procedure, were used to perform palladium-catalyzed cross-coupling reactions, followed by addition of thionyl chloride and pyridine, 1,4-disubstituted or 1,1,4-trisubstituted 1,3-enynes were obtained in a one-pot protocol.
- Cabezas, Jorge A.,Poveda, Rebeca R.,Brenes, José A.
-
p. 3307 - 3321
(2018/09/04)
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- Transformation of Carbonyl Compounds into Homologous Alkynes under Neutral Conditions: Fragmentation of Tetrazoles Derived from Cyanophosphates
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Cyanophosphates (CPs) can be easily prepared from either ketones or aldehydes, and their reaction with NaN3-Et3N·HCl results in the formation of azidotetrazoles. Under microwave irradiation, successive fragmentation of the azidotetrazoles generates alkylidene carbenes that undergo [1,2]-rearrangement and are transformed into homologous alkynes. Treatment of ketone-derived CPs with TMSN3 and Bu2SnO as catalyst in toluene at reflux directly yields the corresponding internal alkynes, whereas the reaction of aldehyde-derived CPs with NaN3-Et3N·HCl in THF at reflux or TMSN3-Bu2SnO (cat.) in toluene at reflux provides homologous terminal alkynes in good yields. These reactions take place under neutral conditions and can be successfully extended to obtain alkynes that are not usually accessible from the corresponding carbonyl compounds by the Ohira-Bestmann or Shioiri procedures, which require basic conditions.
- Yoneyama, Hiroki,Numata, Masahiro,Uemura, Kenji,Usami, Yoshihide,Harusawa, Shinya
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p. 5538 - 5556
(2017/06/07)
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- First synthesis of both 1-aryl-4-[(E)-alk-1-enyl]-1H-1,2,3-triazoles and 1-aryl-4-[(Z)-1-(trimethylsilyl)alk-1-enyl]-1H-1,2,3-triazoles: assembly of π-extended 1,2,3-triazoles using a cross-coupling/click reaction sequence
-
A practical and general synthetic approach to a series of π-extended 1,2,3-triazoles with both aryl and alkenyl moieties on the triazole ring is described. Synthesis of 1-aryl-4-[(E)-alk-1-enyl]-1H-1,2,3-triazoles can be achieved by the click reaction between terminal conjugated (E)-enynes, prepared by copper-mediated cross-coupling reaction of (E)-alk-1-enyldisiamylboranes with (trimethylsilyl)ethynyl bromide, and aryl azides, prepared from arylboronic acids and sodium azide in another flask and employed for the following click reaction without any purification. 1-Aryl-4-[(Z)-1-(trimethylsilyl)alk-1-enyl]-1H-1,2,3-triazoles can be also synthesized by a sequential three-step reaction, which involves copper-mediated cross-coupling reaction of (Z)-1-(trimethylsilyl)alk-1-enyldicyclohexylboranes with (trimethylsilyl)ethynyl bromide to form (Z)-1,3-bis(trimethylsilyl)alk-3-en-1-ynes, deprotection of the trimethylsilyl group on the alkynyl carbon atom to generate (Z)-3-(trimethylsilyl)alk-3-en-1-ynes and click reaction with aryl azides prepared in the same manner as described above. Both synthetic routes are tolerant of a wide range of functional groups with moderate to good yields.
- Oikawa, Asuka,Kindaichi, Gan,Shimotori, Yasutaka,Hoshi, Masayuki
-
p. 4205 - 4213
(2016/07/06)
-
- Development of Non-C2-symmetric ProPhenol Ligands. the Asymmetric Vinylation of N-Boc Imines
-
The development and application of a new generation of non-C2-symmetric ProPhenol ligands is reported herein. Rational design of the ProPhenol ligand paved the way to the first catalytic and asymmetric vinylation of N-Boc imines via hydrozirconation giving rise to valuable allylic amines in excellent yields and enantioselectivities. The utility of this method was demonstrated by developing the shortest reported asymmetric synthesis of the selective serotonine reuptake inhibitor (SSRI) (-)-dapoxetine.
- Trost, Barry M.,Hung, Chao-I,Koester, Dennis C.,Miller, Yan
-
supporting information
p. 3778 - 3781
(2015/08/18)
-
- The Dual Role of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) in the Synthesis of Terminal Aryl- and Styryl-Acetylenes via Umpolung Reactivity
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The dual role of the bicyclic amidine base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was demonstrated in a synthesis of terminal aryl- and styryl-acetylenes. Mechanistically, a tandem process involving elimination/Umpolung/protonation occurs in a single step to generate terminal aryl- and styryl-acetylenes from geminal dibromoalkenes. The key to the success of this transformation lies in the organobase-mediated generation of the acetylide from the 1-bromoalkynes at room temperature. The unique characteristics of DBU as an inherently safer reagent make it an attractive alternative to previous systems wherein required pyrophoric reagents and nonambient temperatures remain unsolved issues. The procedure does not work for the synthesis of alkyl-acetylenes.
- Morri, Ashok Kumar,Thummala, Yadagiri,Doddi, Venkata Ramana
-
supporting information
p. 4640 - 4643
(2015/09/28)
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- Regioselective hydrations of 1-aryl-3-en-1-ynes using gold and platinum catalysts: Selective production of 2-en-1-ones and 3-en-1-ones
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Regiocontrolled hydrations of 1-aryl-3-en-1-ynes have been accomplished with IPrAuOTf and PtCl2/CO to yield 3-en-1-ones and 2-en-1-ones efficiently; our experimental data indicates that the sizes of catalysts play an important role. This journa
- Mokar, Bhanudas Dattatray,Liu, Rai-Shung
-
p. 8966 - 8969
(2014/08/05)
-
- One-pot synthesis of 1-arylmethyl-4-[(E)-alk-1-enyl]-1H-1,2,3-triazoles via a cross-coupling/click reaction sequence
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1-Arylmethyl-4-[(E)-alk-1-enyl]-1H-1,2,3-triazoles have been synthesized from terminal conjugated (E)-enynes, prepared by copper-mediated cross-coupling reaction of (E)-alk-1-enyldisiamylboranes with (trimethylsilyl)ethynyl bromide, benzyl bromides and sodium azide in a one-pot fashion. In this cross-coupling/click reaction sequence, the copper precursor Cu(acac) 2 can serve as a tandem catalyst.
- Hoshi, Masayuki,Okimoto, Mitsuhiro,Oikawa, Asuka,Miyawaki, Shunsuke,Shimotori, Yasutaka
-
p. 2124 - 2128
(2014/01/06)
-
- Synthesis of polysubstituted enynes through iron-catalyzed carbomagnesiation of conjugated diynes
-
Symmetrical and unsymmetrical conjugated diynes are chemo-, regio-, and stereoselectively carbomagnesiated with a ?Grignard reagent at room temperature in the presence of a catalytic amount of FeCl2 without the need for an external ligand. The resulting magnesium intermediate can be further functionalized to give polysubstituted 1,3-enyne derivatives. Georg Thieme Verlag Stuttgart New York.
- Ilies, Laurean,Yoshida, Takumi,Nakamura, Eiichi
-
supporting information
p. 527 - 530
(2014/03/21)
-
- Lithium binaphtholate-catalyzed enantioselective enyne addition to ketones: Access to enynylated tertiary alcohols
-
A new catalytic enantioselective enyne addition to ketones has been developed. In the presence of chiral lithium binaphtholate, the addition reaction proceeded smoothly to produce a series of enynylated tertiary alcohols in up to 96% yield and 94% enantiomeric excess. Convenient transformation of the adduct via Pauson-Khand cycloaddition reaction afforded the bicyclic product without detectable loss of enantioselectivity. Furthermore, catalytic asymmetric enyne addition to trifluoromethylketone was applied in the synthesis of the Efavirenz analogue.
- Cai, Hua,Nie, Jing,Zheng, Yan,Ma, Jun-An
-
p. 5484 - 5493
(2014/07/08)
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- Formation of quaternary stereogenic centers by copper-catalyzed asymmetric conjugate addition reactions of alkenylaluminums to trisubstituted enones
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Alkenylaluminums undergo asymmetric copper-catalyzed conjugate addition (ACA) to β-substituted enones allowing the formation of stereogenic all-carbon quaternary centers. Phosphinamine-copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β-substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl- and alkyl-substituted alkenyl nucleophiles. Moreover, alkyl-substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu-catalyzed ACA. Chiral synthesis made easy: The copper-catalyzed conjugate addition of alkenylaluminum reagents to 3-substituted cyclic enones allows for the formation of all-carbon chiral quaternary centers (see scheme; CuTC=copper(I) thiophene-2-carboxylate). Chiral phosphinamine (SimplePhos) ligands were found to be highly efficient for this transformation.
- Mueller, Daniel,Alexakis, Alexandre
-
supporting information
p. 15226 - 15239
(2013/11/06)
-
- Expeditious cascade reactions: Controlled syntheses of fenestradienes and cyclooctatrienes under palladium catalysis
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Palladium cyclization cascades represent an elegant way to access complex polycyclic scaffolds in a minimum amount of steps. Herein we provide a complete account on two new methodologies including these kind of cascades, each leading to two types of attractive compounds, cyclooctatrienes and [4.6.4.6] fenestradienes. The reader will first discover a strategy requiring three steps starting from alkenyl bromides, based on a first 4-exo-dig carbopalladation/ Sonogashira coupling tandem reaction, and a subsequent P-2 Ni induced semi-hydrogenation. This leads to a first generation of cyclooctatrienes and [4.6.4.6]fenestradienes. Next, the second approach will be presented, in which the second generation of these compounds is accessed in a one-pot reaction including five steps, starting from the same alkenyl bromide compounds. These methods are appealing in terms of atom economy, the use of easy to handle conditions as well as the variability of its scope.
- Charpenay, Mélanie,Boudhar, Aicha,Hulot, Catherine,Blond, Ga?lle,Suffert, Jean
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p. 7568 - 7591
(2013/08/23)
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- Homo- and heterocoupling of terminal conjugated enynes: One-pot synthesis of alka-1,7-diene-3,5-diynes and alk-1-ene-3,5-diynes via two types of coupling reaction
-
Conjugated dienediynes and enediynes with definite geometry- have been prepared in a one-pot manner. This protocol involves two types of coupling reaction, a Suzuki-type coupling and either a Hay coupling or a Cadiot-Chodkiewicz coupling. Thus, the copper
- Hoshi, Masayuki,Okimoto, Mitsuhiro,Nakamura, Shingo,Takahashi, Shinya
-
experimental part
p. 3839 - 3847
(2012/01/04)
-
- Synthesis of 1,3,5-trisubstituted pyrazolines via Zn(ii)-catalyzed double hydroamination of enynes with aryl hydrazines
-
An efficient Zn(ii)-catalyzed intermolecular double hydroamination of 1,3-enynes with aryl hydrazines, for the synthesis of pyrazolines, has been discussed.
- Patil, Nitin T.,Singh, Vipender
-
supporting information; experimental part
p. 11116 - 11118
(2011/11/29)
-
- One-pot synthesis of conjugated (E)-enynones via two types of cross-coupling reaction
-
(Trimethylsilyl)ethynyl bromide can be easily transformed into conjugated (E)-enynones, whose skeleton consists of consecutive carbonyl, ethynyl, and (E)-ethenyl units, via a one-pot multicomponent Suzuki-type reaction-Sonogashira reaction sequence. Thus,
- Hoshi, Masayuki,Yamazaki, Hirokazu,Okimoto, Mitsuhiro
-
experimental part
p. 2461 - 2464
(2010/11/18)
-
- Probing E/Z isomerization on the C10H8 potential energy surface with ultraviolet population transfer spectroscopy
-
The excited-state dynamics of phenylvinylacetylene (1-phenyl-1-buten-3-yne, PVA) have been studied using laser-induced fluorescence spectroscopy, ultraviolet depletion spectroscopy, and the newly developed method of ultraviolet population transfer spectroscopy. Both isomers of PVA (E and Z) show a substantial loss in fluorescence intensity as a function of excitation energy. This loss in fluorescence was shown to be due to the turn-on of a nonradiative process by comparison of the laser-induced fluorescence spectrum to the ultraviolet depletion spectrum of each isomer, with a threshold 600 cm -1 above the electronic origin in Z-PVA and 1000 cm-1 above the electronic origin in E-PVA. Ab initio and density functional theory calculations have been used to show that the most likely source of the nonradiative process is from the interaction of the ππ* state with a close lying πσ* state whose minimum energy structure is bent along the terminal CCH group. Ultraviolet population transfer spectroscopy has been used to probe the extent to which excited-state isomerization is facilitated by the interaction with the πσ* state. In ultraviolet population transfer spectroscopy, each isomer was selectively excited to vibronic levels in the S1 state with energies above and below the threshold for fluorescence quenching. The ultraviolet-excited populations are then recooled to the zero point levels using a reaction tube designed to constrain the supersonic expansion and increase the collision cooling capacity of the expansion. The new isomeric distribution was detected in a downstream position using resonant-2-photon ionization spectroscopy. From these spectra, relative isomerization quantum yields were calculated as a function of excitation energy. While the fluorescence quantum yield drops by a factor of 50-100, the isomerization quantum yields remain essentially constant, implying that the nonradiative process does not directly involve isomerization. On this basis, we postulate that isomerization occurs on the ground-state potential energy surface after internal conversion. In these experiments, the isomerization to naphthalene was not observed, implying a competition between isomerization and cooling on the ground-state potential energy surface.
- Newby, Josh J.,Mueller, Christian W.,Liu, Ching-Ping,Zwier, Timothy S.
-
experimental part
p. 1611 - 1620
(2010/04/04)
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- Synthesis of 4-aryl- and 4-alkyl-2-silyl-1,3-butadienes and their Diels-Alder/cross-coupling reactions
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An ene-yne cross methasis of silyl-substituted alkynes and alkenes has been developed as a route to 4-aryl- and 4-alkyl-2-silyl-substituted 1,3-dienes. The dienes prepared were used to affect highly diastereoselective Diels-Alder reactions and then the silicon-substituted Diels-Alder cycloadducts were used in Hiyama cross-coupling reactions. The cross-coupling reactions enable these silicon dienes to be used as synthons for a variety of other dienes one might prepare and need access to. Two of the silicon-substituted Diels-Alder cycloadducts and one of the Hiyama cross-coupling products were also characterized by X-ray crystallography.
- Junker, Christopher S.,Welker, Mark E.,Day, Cynthia S.
-
scheme or table
p. 8155 - 8165
(2011/03/18)
-
- SYNTHESIS OF FR901464 AND ANALOGS WITH ANTITUMOR ACTIVITY
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The present invention provides novel analogs of FR901464, as well as an improved methodology for preparing FR901464 and its analogs. These compounds display an anti-cancer activity and are candidates for therapies against a number of disease states associ
- -
-
Page/Page column 9
(2008/06/13)
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- Synthesis of bis(alk-3-en-1-ynyl)benzene with either E- or Z-configuration via a one-pot three-component coupling reaction and its optical properties
-
A convenient, efficient and stereoselective synthesis of a range of bis(alk-3-en-1-ynyl)benzenes with E- and Z-configuration is described. The protocol involves Cu-mediated cross-coupling reaction of (E)- and (Z)-alk-1-enyldisiamylboranes with (trimethyls
- Hoshi, Masayuki,Suzuki, Souichi,Saitoh, Shingo,Okimoto, Mitsuhiro,Shirakawa, Kazuya
-
p. 119 - 124
(2007/10/03)
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- Total syntheses, fragmentation studies, and antitumor/antiproliferative activities of FR901464 and its low picomolar analogue
-
FR901464 is a potent anticancer natural product that lowers the mRNA levels of oncogenes and tumor suppressor genes. In this article, we report a convergent enantioselective synthesis of FR901464, which was accomplished in 13 linear steps. Central to the synthetic approach was the diene-ene cross olefin metathesis reaction to generate the C6-C7 olefin without the use of protecting groups as the final step. Additional key reactions include a Zr/Ag-promoted alkynylation to set the C4 Stereocenter, a mild and chemoselective Red-Al reduction, a reagent-controlled stereoselective Mislow-Evans-type [2,3]-sigmatropic rearrangement to install the C5 Stereocenter, a Carreira asymmetric alkynylation to generate the C4′ stereocenter, and a highly efficient ring-closing metathesis-allylic oxidation sequence to form an unsaturated lactone. The decomposition pathways of FR901464's right fragment were studied under physiologically relevant conditions. Facile epoxide opening by β-elimination gave two enones, one of which could undergo dehydration via its hemiketal to form a furan. To prevent this decomposition pathway, a right fragment was rationally designed and synthesized. This analogue was 12 times more stable than the right fragment of the natural product. Using this more stable right fragment analogue, an FR901464 analogue, meayamycin, was prepared in 13 linear steps. The inhibitions of human breast cancer MCF-7 cell proliferation by synthetic FR901464 and meayamycin were studied, and the GI50 values for these compounds were determined to be 1.1 nM and 10 pM, respectively. Thus, meayamycin is among the most potent anticancer small molecules that do not bind to either DNA or microtubule.
- Albert, Brian J.,Sivaramakrishnan, Ananthapadmanabhan,Naka, Tadaatsu,Czaicki, Nancy L.,Koide, Kazunori
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p. 2648 - 2659
(2007/10/03)
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- Construction of terminal conjugated enynes: Cu-mediated cross-coupling reaction of alkenyldialkylborane with (trimethylsilyl)ethynyl bromide
-
The cross-coupling reaction of (E)- and (Z)-alk-1-enyldialkylborane with (trimethylsilyl)ethynyl bromide proceeds in the presence of a catalytic amount of copper(II) acetylacetonate and a base under extremely mild conditions to provide conjugated enynes w
- Hoshi, Masayuki,Kawamura, Noritsugu,Shirakawa, Kazuya
-
p. 1961 - 1970
(2007/10/03)
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- Stereoselective syntheses of (E)- and (Z)-1-arylalk-3-en-1-ynes and (E,E)-, (Z,E)-, (E,Z)-, and (Z,Z)-alka-1,5-dien-3-ynes via a one-pot multicomponent coupling reaction
-
Both 1-arylalk-3-en-1-ynes and alka-1,5-dien-3-ynes have been synthesized under extremely mild reaction conditions in good to high yields via a sequential Suzuki-type and Sonogashira reaction in a one-pot manner. Thus, the protocol involves Cu-mediated cross-coupling reaction of (E)- or (Z)- alkenyldisiamylborane with (trimethylsilyl)ethynyl bromide in the presence of 1M NaOMe and Pd/Cu-catalyzed cross-coupling reaction with aryl or alkenyl iodide in the presence of aqueous n-Bu4NOH. The reaction with aryl iodide is tolerant of a wide variety of functional groups on the aromatic ring and leads to the stereoselective formation of (E)- and (Z)-1-arylalk-3-en-1-ynes. In addition, the reactions with (E)- and (Z)-1-iodoalk-1-enes have accomplished the construction of all possible combinations of geometrical isomers, (E,E)-, (Z,E)-, (E,Z)-, and (Z,Z)-alka-1,5-dien-3-ynes. Georg Thieme Verlag Stuttgart.
- Hoshi, Masayuki,Nakayabu, Hidenori,Shirakawa, Kazuya
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p. 1991 - 2007
(2007/10/03)
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- (Z)-Selective cross-dimerization of arylacetylenes with silylacetylenes catalyzed by vinylideneruthenium complexes
-
The vinylideneruthenium(II) complexes bearing bulky and basic tertiary phosphine ligands, RuCl2(=C=CHPh)L2 (L = PPr i3, PCy3), serves as a good catalyst precursor for (Z)-selective cross-dimerization between arylacetylenes and silylacetylenes in the presence of N-methylpyrrolidine. The Royal Society of Chemistry 2005.
- Katayama, Hiroyuki,Yari, Hiroshi,Tanaka, Masaki,Ozawa, Fumiyuki
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p. 4336 - 4338
(2008/02/08)
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- Flash vacuum pyrolysis of 1,6-diphenyl-1,5-hexadien-3-ynes: Tandem diaryldienyne cyclizations to form chrysene
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Flash vacuum pyrolysis of 1,6-diphenyl-1,5-hexadien-3-yne at 1000°C and its bromo derivative at 800°C yielded chrysene as the major product through tandem diaryldienyne cyclizations.
- Sonoda, Motohiro,Itahashi, Kayo,Tobe, Yoshito
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p. 5269 - 5272
(2007/10/03)
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- Construction of terminal conjugated enynes: Regio- and stereoselective syntheses of 3-alken-1-ynes and 1-trimethylsilyl-3-alken-1-ynes from alkenyldialkylboranes and (trimethylsilyl)ethynyl bromide
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The cross-coupling reaction of (E)- and (Z)-1-alkenyldialkylboranes with (trimethylsilyl)ethynyl bromide proceeds in the presence of a base and a catalytic amount of Cu(acac)2 under very mild conditions to provide conjugated enynes whose carbon
- Hoshi, Masayuki,Shirakawa, Kazuya
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p. 1101 - 1104
(2007/10/03)
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- Dramatic enhancement of reactivity of organosilicon compounds induced by complexation of bis(allyl)silanes with fluoride ion
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New type of fluoride ion catalyzed allylation agent (1a, 1b), allenylation agent (9, 10), and alkynylation agent (17) can be successfully utilized for various carbonyl substrates. The rate acceleration is ascribable to the shift of equilibrium to the chel
- Shibato, Atsushi,Itagaki, Yoshifumi,Tayama, Eiji,Hokke, Yasutoshi,Asao, Naoki,Maruoka, Keiji
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p. 5373 - 5382
(2007/10/03)
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- A one-pot procedure for the synthesis of alkynes and bromoalkynes from aldehydes
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Alkynes R-C≡CH were obtained in good yield through a one-pot procedure by a sequence of reactions starting from a Wittig-type condensation of the aldehydes RCHO with the ylide derived from dibromomethyltriphenylphosphonium bromide 5. The same reactions could also be used to prepare the intermediate dibromoalkenes RCH=CBr2, and in certain cases, the bromoalkynes R-C≡CBr.
- Michel, Patrick,Gennet, Dominique,Rassat, Andre
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p. 8575 - 8578
(2007/10/03)
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- Addition and cyclization reactions in the thermal conversion of hydrocarbons with an enyne structure, 4: Formation and rearrangements of bicyclic C10H8 aromatics from 1-phenyl-1-buten-3-yne
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The thermal conversion of 1-phenyl-1-buten-3-yne (1) into the cycloisomerization products naphthalene (2), azulene (3), and 1-methylene-1H-indene (4) has been studied at temperatures between 550 and 1000°C, a reaction time of approximately 0.3 s at 13 Tor
- Schulz, Kathrin,Hofmann, Joerg,Zimmermann, Gerhard
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p. 2535 - 2539
(2007/10/03)
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- Radical-Stabilization-Energy - the MMEVBH Force Field
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Making use of the VB method of Malrieu et al. a force field has been developed, which allows to calculate heats of formation of hydrocarbons (conjugated and non-conjugated olefins, radicals and diradicals) with high accuracy.With this method radical stabilization energies (RSE) for a great number of delocalized radicals are calculated and compared with experimental values, derived from shock-tube measurements of dissociation energies or from rotational barriers of substituted olefins.A detailed analysis of the RSE with respect to structure, substituents, strain, and aromaticity is presented. - Key Words: Resonance energy / Heats of formation / Single pulse shock tube / Intrisic rotational barrier
- Roth, Wolfgang R.,Staemmler, Volker,Neumann, Martin,Schmuck, Carsten
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p. 1061 - 1118
(2007/10/02)
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- Conversion of 2-alkenylcyclopropylcarbenechromium complexes to 5-alkenyl-2-cyclopentenones: A stereospecific three- To fivecarbon ring expansion reaction
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Upon thermolysis, 2-alkenylcyclopropylcarbene-chromium complexes are converted to 5-alkenyl-2-cyclopentenones. The reaction appears to proceed with retention of configuration in the absence of steric factors.
- Herndon, James W.,Hill, David K.,McMullen, Leonard A.
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p. 5687 - 5690
(2007/10/02)
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- General synthesis of retinoids and arotinoids via palladium-catalyzed cross-coupling of boronic acids with electrophiles
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A novel approach to the synthesis of retinoids and arotinoids (including heterocyclic analogs) is described which is based on the thallium-accelerated palladium-catalyzed cross-coupling of boronic acids with a variety of electrophiles (the Suzuki reaction).
- Torrado,Lopez,Alvarez,De Lera
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p. 285 - 293
(2007/10/02)
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- Flash Vacuum Pyrolysis of Stabilised Phosphorous Ylides. Part 6. Pyrolysis of Substituted Cinnamoyl Ylides as a Route to Conjugated Enynes
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The substituted cinnamoyl ylides 6 and 7, readily prepared in one step from the quaternary phosphonium salts 8 and cinnamoyl chlorides 9, undergo extrusion of Ph3PO upon FVP to give the 1,3-enynes 12 and 13 in moderate yield.At 500 deg C there is little double bond isomerisation, but at 700 deg C this does occur to give almost 1:1 mixtures of E and Z isomers.In a few cases, including those with a nitrophenyl group present, the yields are poor or the reactions fail stabilised ylide was only partly successful since the severe conditions required for loss of the ester group resulted in significant isomerisation to naphthalene.The fully assigned 13C NMR spectra for 20 enynes are reported.One examples of the isomeric β,γ-unsaturated-δ-oxo ylides, 14 has been prepared and is found to undergo loss of Ph3P on FVP at 700 deg C to give indene and benzene in low yield.
- Aitken, R. Alan,Boeters, Christine,Morrison, John J.
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p. 2473 - 2480
(2007/10/02)
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- A stereoselective synthesis of 1-phenyl-1-buten-3-yne and some 1-heteroaryl analogues
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Z-Enynes, RCH=CHC≡CH (R= phenyl, 2-furyl, 2- and 3-thienyl and 3-pyridyl) can be obtained in ~ 40% overall yields and with a stereoselectivity of> 95% by Pd/Cu-catalyzed cross-coupling of the readily available enyne sulfide HC≡CCH=CHSC2H5
- Fossatelli, Marco,Van Der Kerk, Anca C. T. H. M.,Vasilevsky, Sergei F.,Brandsma, Lambert
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p. 4229 - 4232
(2007/10/02)
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- Stereoselective synthesis of naturally-occurring 7-(hetero)aryl (2E,4E,6E)-2,4,6-heptatrienamides and their structural analogues
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A new and efficient highly stereoselective method to prepare naturally-occurring 7-(hetero)aryl (2E,4E,6E)-2,4,6-heptatrienamides and their structural analogues has been developed. The physical and spectral properties of one of these compounds, i.e. (2E,4E,6E)-7-(2-thienyl)-2,4,6-heptatrienoic acid piperidide (4b), have been found to be quite different from those previously reported for 7-(-2-thienyl)-2,4,6,-heptatrienoic acid piperidide isolated from Othantus maritimus to which the (2E,4E,6E)-configuration had been previously assigned.
- Rossi,Carpita,Lippolis
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p. 333 - 349
(2007/10/02)
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- Alkine und Cumulene, XV. Ueber die Photodimerisierung konjugierter Enine
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On irradiation in the presence of triplet sensitizers having a triplet energy >250 KJ/mol, vinylacetylene (1a) dimerizes to cis- and trans-1,2-diethynylcyclobutane (cis- and trans-2) as well as minor amounts of 4-ethynyl-1-vinylcyclobutene (3).The effect of substituents on the course of the reaction is investigated: whereas alkyl, vinyl, and phenyl substituents, respectively, in the 4-position of 1a do not influence the photoaddition, 2-substituted enynes yield the corresponding cyclobutanes in poor yields only.Finally, 1-substituted vinylacetylenes (besides the substituents mentioned above the influence of ethynyl, chloro, and methoxy groups has been investigated) do not provide photodimers; they are cis-trans-isomerized instead.The mechanism of the photoaddition is discussed.
- Eisenhuth, Ludwig,Siegel, Herbert,Hopf, Henning
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p. 3772 - 3788
(2007/10/02)
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