- A stereoselective synthetic route to (Z)-α-organostannyl-α,β-unsaturated carbonyl compounds
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Hydrozirconation of acetylenic stannanes 1 affords gemstannazirconocene alkenes 2. Intermediates 2 are treated with acyl halides to obtain (Z)-α-organostannyl-α,β-unsaturated carbonyl compounds 3 via Zr-Cu transmetallation.
- Zhong, Ping,Xiong, Zhi-Xing,Huang, Xian
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- Selective Cross-Dehydrogenative C(sp3)-H Arylation with Arenes
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Selective C(sp3)-C(sp2) bond construction is of central interest in chemical synthesis. Despite the success of classic cross-coupling reactions, the cross-dehydrogenative coupling between inert C(sp3)-H and C(sp2)-H bonds represents an attractive alternative toward new C(sp3)-C(sp2) bonds. Herein, we establish a selective inter-and intramolecular C(sp3)-H arylation of alcohols with nondirected arenes that thereby provides a general pathway to access a wide range of β-arylated alcohols, including tetrahydronaphthalen-2-ols and benzopyran-3-ols, with high to excellent chemo-and regioselectivity.
- Hao, Hong-Yan,Mao, Yang-Jie,Xu, Zhen-Yuan,Lou, Shao-Jie,Xu, Dan-Qian
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p. 2396 - 2402
(2020/03/13)
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- Stereospecific Decarboxylative Nazarov Cyclization Mediated by Carbon Dioxide for the Preparation of Highly Substituted 2-Cyclopentenones
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Highly substituted 2-cyclopentenones were stereospecifically and regioselectively constructed with high catalytic efficiency through Lewis-acid catalyzed decarboxylative Nazarov cyclization of the cyclic carbonate derivative, which is prepared by reacting the propargyl alcohol with carbon dioxide in the presence of a silver catalyst. The stereochemistry of the 2-cyclopentenone is strictly controlled by the geometry of the alkene in the starting material. This method is applicable for various substrates.
- Komatsuki, Keiichi,Sadamitsu, Yuta,Sekine, Kohei,Saito, Kodai,Yamada, Tohru
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p. 11594 - 11598
(2017/09/11)
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- Enantioselective synthesis of β-substituted chiral allylic amines: Via Rh-catalyzed asymmetric hydrogenation
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An asymmetric mono-hydrogenation of 2-acetamido-1,3-dienes catalyzed by a Rh-DuanPhos complex has been developed. This approach provides easy access to chiral allylic amines with excellent enantioselectivities and high regioselectivities. The products are valuable chiral building blocks for pharmaceuticals.
- Wang, Qingli,Gao, Wenchao,Lv, Hui,Zhang, Xumu
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p. 11850 - 11853
(2016/10/07)
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- Acid-catalyzed synthesis of α,β-disubstituted conjugated enones by a Meyer-Schuster-type rearrangement in allenols
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A novel, direct and simple methodology to gain access to α,β-disubstituted conjugated enones from α-allenols in a sustainable metal catalysis context, considering the inexpensiveness and environmentally friendliness of iron(III) species and protons, has b
- Alcaide, Benito,Almendros, Pedro,Cembellín, Sara,Martínez Del Campo, Teresa
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p. 1070 - 1078
(2015/03/30)
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- Preparation of 1-methyl-3-phenylisoquinoline derivatives from oximes using polyphosphoric esters
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We show a beneficial new approach to the preparation of 1-methyl-3-phenylisoquinoline derivatives. This method involves heating polyphosphate ester and the appropriate oximes obtained from 3,4-diphenylbut-3-en-2-one derivatives. The isoquinolines were syn
- Niemczak, Micha?,Czerniak, Kamil,Kopczyński, Tomasz
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p. 1868 - 1873
(2015/03/18)
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- Copper-catalyzed regio- and stereoselective intermolecular three-component oxyarylation of allenes
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A copper(II)-catalyzed intermolecular three-component oxyarylation of allenes using arylboronic acids as a carbon source and TEMPO as an oxygen source is described. The reaction proceeded under mild conditions with high regio- and stereoselectivity and functional group tolerance. A plausible reaction mechanism is proposed, involving carbocupration of allenes, homolysis of the intervening allylcopper(II), and a radical TEMPO trap.
- Itoh, Taisuke,Shimizu, Yohei,Kanai, Motomu
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supporting information
p. 2736 - 2739
(2014/06/09)
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- Synthesis and antimicrobial evaluation of some pyrazole derivatives
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Reaction of a series of (E)-3-phenyl-4-(p-substituted phenyl)-3-buten-2- ones with p-sulfamylphenyl hydrazine in glacial acetic acid gave the corresponding hydrazones, subsequent treatment of which with 30% HCl afforded pyrazole-1-sulphonamides. On the ot
- Sharshira, Essam Mohamed,Hamada, Nagwa Mohamed Mahrous
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scheme or table
p. 4962 - 4971
(2012/09/22)
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- Iridium-catalyzed asymmetric hydrogenation of α-substituted α,β-unsaturated acyclic ketones: Enantioselective total synthesis of (-)-mesembrine
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A highly efficient asymmetric hydrogenation of α-substituted α,β-unsaturated acyclic ketones catalyzed by chiral spiro iridium complexes for the preparation of chiral 2-substituted allylic alcohols has been developed (ee up to 99.7%). This method provides a concise route to (-)-mesembrine (34% yield, 12 steps).
- Zhang, Qian-Qian,Xie, Jian-Hua,Yang, Xiao-Hui,Xie, Jian-Bo,Zhou, Qi-Lin
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supporting information
p. 6158 - 6161
(2013/02/23)
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- H2SO4-promoted synthesis of (E)-stilbenes from substituted phenylacetones and substituted benzaldehydes through tandem aldol-Grob reaction
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Stilbene derivates (stilbenoids) are present in plants and show a wide range of biological activities and potential therapeutic value. In continuation of our natural product synthesis program, an efficient, simple, and practical method has been developed to regioselectively synthesize (E)-stilbenes using H2SO4 as a catalyst in a short time (30-60 s) at room temperature in good to excellent yields.
- Narender,Papi Reddy,Tiwari, Sriniwas
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scheme or table
p. 1572 - 1583
(2011/06/27)
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- CuH-catalyzed enantioselective 1,2-reductions of α,β-unsaturated ketones
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The first study on a general technology for arriving at valued nonracemic allylic alcohols using asymmetric ligand-accelerated catalysis by copper hydride is described.
- Moser, Ralph,Boskovia, Zarko V.,Crowe, Christopher S.,Lipshutz, Bruce H.
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supporting information; experimental part
p. 7852 - 7853
(2010/08/04)
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- Enantioselective reduction of ketones and imines catalyzed by (CN-Box)ReV-oxo complexes
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The development and application of chiral, non-racemic ReV-oxo complexes to the enantioselective reduction of prochiral ketones is described. In addition to the enantioselective reduction of prochiral ketones, we report the application of these complexes to 1) a tandem Meyer-Schuster rearrangement/reduction to access enantioenriched allylic alcohols and 2) the enantioselective reduction of imines.
- Nolin, Kristine A.,Ahn, Richard W.,Kobayashi, Yusuke,Kennedy-Smith, Joshua J.,Toste, F. Dean
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supporting information; experimental part
p. 9555 - 9562
(2010/10/03)
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- Palladium-catalyzed oxidative cross-coupling reaction of arylboronic acids with diazoesters for stereoselective synthesis of (E)-α,β- diarylacrylates
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A Pd-catalyzed oxidative cross-coupling reaction of arylboronic acids with α-diazoesters was achieved using molecular oxygen as the sole reoxidant, and E-α,β-diarylacrylates were obtained in good yields and >20:1 E-to-Z selectivity.
- Tsoi, Yuk-Tai,Zhou, Zhongyuan,Chan, Albert S. C.,Yu, Wing-Yiu
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supporting information; experimental part
p. 4506 - 4509
(2010/12/25)
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- Characterization of route specific impurities found in methamphetamine synthesized by the Leuckart and reductive amination methods
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Impurity profiling of seized methamphetamine can provide very useful information in criminal investigations and, specifically, on drug trafficking routes, sources of supply, and relationships between seizures. Particularly important is the identification of "route specific" impurities or those which indicate the synthetic method used for manufacture in illicit laboratories. Previous researchers have suggested impurities which are characteristic of the Leuckart and reductive amination (Al/Hg) methods of preparation. However, to date and importantly, these two synthetic methods have not been compared in a single study utilizing methamphetamine hydrochloride synthesized in-house and, therefore, of known synthetic origin. Using the same starting material, 1-phenyl-2-propanone (P2P), 40 batches of methamphetamine hydrochloride were synthesized by the Leuckart and reductive amination methods (20 batches per method). Both basic and acidic impurities were extracted separately and analyzed by GC/MS. From this controlled study, two route specific impurities for the Leuckart method and one route specific impurity for the reductive amination method are reported. The intra- and inter-batch variation of these route specific impurities was assessed. Also, the variation of the "target impurities" recently recommended for methamphetamine profiling is discussed in relation to their variation within and between production batches synthesized using the Leuckart and reductive amination routes.
- Kunalan, Vanitha,Daeid, Niamh Nic,Kerr, William J.,Buchanan, Hilary A. S.,McPherson, Allan R.
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experimental part
p. 7342 - 7348
(2010/04/06)
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- A nonsymmetric pincer-catalyzed Suzuki-Miyaura arylation of benzyl halides and other nonactivated unusual coupling partners
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(Chemical Equation Presented) The catalytic activity of a PCN-type palladium pincer complex is evaluated in the construction of C(sp 2)-C(sp2) and C(sp2)-C(sp3) bonds by Suzuki-Miyaura cross-couplings employing nontypical substrates such as benzyl halides, α-haloenones, or alkylboronic acids as coupling partners. Most of the reported reactions are achieved in aqueous media, with all of the advantages implied.
- Ines, Blanca,Moreno, Isabel,SanMartin, Raul,Dominguez, Esther
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supporting information; experimental part
p. 8448 - 8451
(2009/04/11)
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- Highly enantioselective synthesis of optically active ketones by iridium-catalyzed asymmetric hydrogenation
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(Chemical Equation Presented) Close to perfect enantioselectivity (up to 99% ee, see scheme) is found for the formation of α-substituted ketones by the asymmetric hydrogenation of enones with an iridium-phosphinooxazoline catalyst. In an operationally simple process, both linear and cyclic substrates react well and afford the desired products in high yields. A wide variety of substituents are tolerated, thus making the method synthetically appealing.
- Lu, Sheng-Mei,Bolm, Carsten
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supporting information; experimental part
p. 8920 - 8923
(2009/05/30)
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- The α-arylation of α-bromo- and α-chloroenones using palladium-catalysed cross-coupling
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The palladium-catalysed cross-coupling reaction of various arylboronic acids with α-bromoenones and α-chloroenones offers an operationally simple approach to the synthesis of both cyclic and acyclic α-arylenones.
- Banks, James C.,Mele, David Van,Frost, Christopher G.
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p. 2863 - 2866
(2007/10/03)
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- Base-catalyzed ring openings of benzocyclobutenones and -ols
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The base-catalyzed ring opening of a number of isomeric E- and Z-benzylidenebenzocyclobutenones and -ols has been studied in both protic and aprotic solvents.Cleavage of the C1-C2 bond results in the formation of stilbenes with mainly, and at times exclusively, retained stereochemistry.For the alcohols, these results point to an oxyanion-induced carbon-carbon bond cleavage leading to a vinyl anion that is protonated with retention of configuration in the protic solvents rather than to an electrocyclic ring opening to an alkoxy o-quinodimethane.Reaction of the Z isomer of benzylidenebenzocyclobutenol with methyllithium in THF at 20 deg C causes isomerization to the E isomer, cleavage of the C1-C2 bond, and recyclization of the resultant isomerized vinyl anion. - Key words: benzylidenebenzocyclobutenones, base-catalyzed ring opening; benzylidenebenzocyclobutenols, base-catalyzed ring opening.
- Bradley, J. C.,Durst, T.
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p. 1660 - 1665
(2007/10/02)
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- SYNTHESIS OF HETEROCYCLIC COMPOUNDS. XXXVI. PREPARATION OF ALKYL SUBSTITUTED PYRANCARBONITRLES.
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The cyclization of the ketonitriles obtained from the reaction of suitably substituted propenones with propanedinitrile leads to alkyl substituted 4H-pyrans.Some of the starting propenones had to be prepared by base promoted opening of an isoxazole ring in the presence of an aldehyde.An exception to the general synthesis is also reported.
- Soto, Jose L.,Seoane, Carlos,Martin, Nazario,Quinteiro, Margarita
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- Interaction of Fischer carbene complexes of the type W(CO)5[C(OMe)R] (R = CH3, C2H5) with acetylenes
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W(CO)5[C(OMe)CH2R1] (R1 = H, CH3) reacts with PhC2R2 (R2 = Ph, CH3) in toluene at 100°C to give vinyl ethers and enones. The formation of these products can be explained by an exocyclic β-hydride elimination reaction of a metallacyclobutene intermediate.
- Macomber, David W.
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p. 1589 - 1591
(2008/10/08)
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- Aza Cope Rearrangements in the Cyclopropenyl-and Allyl-Substituted Δ2-Oxazolinone Systems
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The scope of the thermal and photochemical reorganization reactions of a number of cyclopropenyl- and allyl- substituted oxazolinones has been examined.These systems undergo a facile sigmatropic rearrangement in accord with orbital symmetry predictions. 2-Methyl-4-allyl-Δ2-oxazolinones were found to undergo a 3,3-sigmatropic allyl shift on thermolysis to give the Δ3-oxazolinone isomer.In contrast, on direct irradiation the 2-methyl-4-allyl-Δ3-oxazolinones undergo a 1,3-allyl shift to give the Δ2-isomer.The 4,4-disubstituted Δ2-oxazolinones undergo decarbonylat ion either on irradiation or by flash vacuum pyrolysis to give acetimides.The acetimides formed were easily hydrolyzed to give the corresponding ketones.The excited-state behavior of the 2-phenyl-4-methyl-Δ2-oxazolinone system was found to be markedly different from that encountered with the 2-methyl-4-phenyl-substituted isomer.The rationale for the difference in behavior is discussed.
- Padwa, Albert,Akiba, Mitsuo,Cohen, Leslie A.,MacDonald, Gavin J.
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p. 695 - 703
(2007/10/02)
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