- Palladium-Catalyzed Asymmetric Tandem Denitrogenative Heck/Tsuji-Trost of Benzotriazoles with 1,3-Dienes
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The asymmetric denitrogenative cycloaddition has emerged as a powerful tool to build chiral aza-heterocyles. However, only one example of asymmetric denitrogenative cycloaddition of benzotriazole with unsaturated hydrocarbons has been explored so far, bec
- Li, Yin-Lin,Wu, Hai-Hong,Zhang, Junliang,Zhang, Pei-Chao
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supporting information
p. 13010 - 13015
(2021/09/07)
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- Lewis acids promoted 3 + 2 cycloaddition of oxaziridines and cyclic allylic alcohols through carbonyl imine intermediates
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Syntheses of isoxazolidines through the carbonyl imine intermediates are currently limited to monosubstituted olefin substrates. Herein, we reported syntheses of novel bicyclic isoxazolidine-containing compounds through 1,3-dipolar cycloaddition reactions
- Zhao, Erbao,Zhou, Feilong,Zhao, Yujun
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p. 4282 - 4293
(2019/04/30)
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- Chemo-Enzymatic Oxidative Rearrangement of Tertiary Allylic Alcohols: Synthetic Application and Integration into a Cascade Process
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A chemo-enzymatic catalytic system, comprised of Bobbitt's salt and laccase from Trametes versicolor, allowed the [1,3]-oxidative rearrangement of endocyclic allylic tertiary alcohols into the corresponding enones under an Oxygen atmosphere in aqueous media. The yields were in most cases quantitative, especially for the cyclopent-2-en-1-ol or the cyclohex-2-en-1-ol substrates without an electron withdrawing group (EWG) on the side chain. Transpositions of macrocyclic alkenols or tertiary alcohols bearing an EWG on the side chain were instead carried out in acetonitrile by using an immobilized laccase preparation. Dehydro-Jasmone, dehydro-Hedione, dehydro-Muscone and other fragrance precursors were directly prepared with this procedure, while a synthetic route was developed to easily transform a cyclopentenone derivative into trans-Magnolione and dehydro-Magnolione. The rearrangement of exocyclic allylic alcohols was tested as well, and a dynamic kinetic resolution was observed: α,β-unsaturated ketones with (E)-configuration and a high diastereomeric excess were synthesized. Finally, the 2,2,6,6-tetramethyl-1-piperidinium tetrafluoroborate (TEMPO+BF4?)/laccase catalysed oxidative rearrangement was combined with the ene-reductase/alcohol dehydrogenase cascade process in a one-pot three-step synthesis of cis or trans 3-methylcyclohexan-1-ol, in both cases with a high optical purity. (Figure presented.).
- Brenna, Elisabetta,Crotti, Michele,De Pieri, Matteo,Gatti, Francesco G.,Manenti, Gabriele,Monti, Daniela
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supporting information
p. 3677 - 3686
(2018/06/04)
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- Preparation of optically active cycloalkenes bearing all-carbon quaternary stereogenic centres: Via lipase-oxovanadium combo-catalysed dynamic kinetic resolution
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In this study, a novel asymmetric synthesis of all-carbon quaternary stereogenic centres is developed by the connection of three prochiral or achiral components - conjugated enones, organometallic compounds and vinyl esters - at the C-1 position of the enones. This method involves three sequential steps: 1,2-nucleophilic addition of an organometallic compound to the enone, lipase-catalysed dynamic kinetic resolution (DKR) of the tert-allylic alcohol and the Ireland-Claisen rearrangement of the optically active allyl ester thus generated. This method features the effective use of acyl moieties installed by DKR for achieving high atom economy. The application of this method to the protective-group-free asymmetric total synthesis of (-)-crinane, a core structure of a class of natural alkaloids, has demonstrated that it can alter a known synthetic pathway of a racemate into an asymmetric synthesis of an optically pure molecule while reducing the total transformation steps and increasing the overall yield. With these advantages, this method is practical and attractive as a new environmentally benign protocol.
- Kawanishi, Shinji,Sugiyama, Koji,Oki, Yasuhiro,Ikawa, Takashi,Akai, Shuji
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supporting information
p. 411 - 417
(2017/08/14)
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- Iodine-Promoted Metal-Free Aromatization: Synthesis of Biaryls, Oligo p-Phenylenes and A-Ring Modified Steroids
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We describe efficient procedures based on the use of iodine for the synthesis of biaryls from arylcyclohexenols or arylcyclohexanols using sub-stoichiometric/catalytic iodine and dimethyl sulfoxide (DMSO) as oxidant. Heteroarylcyclohexanols also produced the corresponding biaryl products. It was proven that biphenyl can also be efficiently obtained when the quantity of iodine was reduced to 0.05 equiv. The method is compatible with different functional groups in the aromatic ring (either electron-donating or electron-withdrawing groups). For substrate scope, apart from cyclohexanone and cyclohexenone, some substituted cyclohexanones were also used to synthesize the starting arylcyclohexanols. The process was applied to the synthesis of oligo p-phenylenes and A-ring aromatized steroids, where the combined use of I2/DMSO not only provoked the necessary migration of the methyl group at C-10, but also further extended the conjugation.
- Domingo, Victoriano,Prieto, Consuelo,Castillo, Alexis,Silva, Lucia,Quílez Del Moral, José F.,Barrero, Alejandro F.
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supporting information
p. 3359 - 3364
(2015/11/03)
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- Catalytic olefin hydroamination with aminium radical cations: A photoredox method for direct C-N bond formation
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While olefin amination with aminium radical cations is a classical method for C-N bond formation, catalytic variants that utilize simple 2° amine precursors remain largely undeveloped. Herein we report a new visible-light photoredox protocol for the intramolecular anti-Markovnikov hydroamination of aryl olefins that proceeds through catalytically generated aminium radical intermediates. Mechanistic studies are consistent with a process involving amine oxidation via electron transfer, turnover-limiting C-N bond formation, and a second electron transfer step to reduce a carbon-centered radical, rendering the overall process redox-neutral. A range of structurally diverse N-aryl heterocycles can be prepared in good to excellent yields under conditions significantly milder than those required by conventional aminium-based protocols.
- Musacchio, Andrew J.,Nguyen, Lucas Q.,Beard, G. Hudson,Knowles, Robert R.
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supporting information
p. 12217 - 12220
(2014/12/09)
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- Palladium-catalyzed oxidative rearrangement of tertiary allylic alcohols to enones with oxygen in aqueous solvent
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A one-pot procedure for Pd(TFA)2-catalyzed 1,3-isomerization of tertiary allylic alcohols to secondary allylic alcohols followed by a Pd(TFA)2/neocuproine-catalyzed oxidative reaction to β-disubstituted-α,β-unsaturated kenones was developed. (Chemical Equation Presented).
- Li, Jingjie,Tan, Ceheng,Gong, Jianxian,Yang, Zhen
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supporting information
p. 5370 - 5373
(2015/01/09)
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- Migratory dynamic kinetic resolution of carbocyclic allylic alcohols
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A novel migratory dynamic kinetic resolution based on the interplay between an enzyme acylation catalyst and a heterogeneous Bronsted acid as an isomerization/racemization catalyst gives rise to carbocyclic allylic esters with excellent stereoselectivity
- Manzuna Sapu, Chicco,G?rbe, Tams,Lihammar, Richard,B?ckvall, Jan-E.,Deska, Jan
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supporting information
p. 5952 - 5955
(2015/02/19)
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- Continuous flow-processing of organometallic reagents using an advanced peristaltic pumping system and the telescoped flow synthesis of (E/Z)-tamoxifen
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A new enabling technology for the pumping of organometallic reagents such as n-butyllithium, Grignard reagents, and DIBAL-H is reported, which utilises a newly developed, chemically resistant, peristaltic pumping system. Several representative examples of its use in common transformations using these reagents, including metal-halogen exchange, addition, addition-elimination, conjugate addition, and partial reduction, are reported along with examples of telescoping of the anionic reaction products. This platform allows for truly continuous pumping of these highly reactive substances (and examples are demonstrated over periods of several hours) to generate multigram quantities of products. This work culminates in an approach to the telescoped synthesis of (E/Z)-tamoxifen using continuous-flow organometallic reagent-mediated transformations.
- Murray, Philip R. D.,Browne, Duncan L.,Pastre, Julio C.,Butters, Chris,Guthrie, Duncan,Ley, Steven V.
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p. 1192 - 1208
(2013/10/08)
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- TARTROL-derived chiral phosphine-phosphite ligands and their performance in enantioselective Cu-catalyzed 1,4-addition reactions
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By using (R,R,R,R)-2,3-dimethoxy-2,3-dimethyl-1,4-dioxane-5,6-bis- diphenylmethanol (TARTROL) as a chiral building block, a set of six modular phosphine-phosphite ligands (with a 1,2-phenylene backbone) were synthesized and evaluated in the Cu-catalyzed a
- Dindaroglu, Mehmet,Akyol, Sema,Simsir, Hamza,Neudoerfl, Joerg-Martin,Burke, Anthony,Schmalz, Hans-Guenther
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p. 657 - 662
(2013/07/11)
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- Pt-catalyzed oxidative rearrangement of cyclic tertiary allylic alcohols to enones using aqueous hydrogen peroxide
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An oxidative rearrangement of cyclic tertiary allylic alcohols to β-disubstituted α,β-unsaturated ketones by Pt black catalyst with aqueous hydrogen peroxide is described. The reaction proceeds under organic solvent- and halide-free conditions and gives only water as a coproduct. The Pt black catalyst is commercially available and can be reused at least four times.
- Nagamine, Takashi,Kon, Yoshihiro,Sato, Kazuhiko
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supporting information; experimental part
p. 744 - 746
(2012/09/22)
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- Cu-catalyzed enantioselective 1,4-additions of aryl-Grignard reagents to cyclohexenone in the presence of TADDOL-derived phosphane-phosphite ligands
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Asymmetric conjugate additions (1,4-additions) of aryl-Grignard reagents to cyclohex-2-enone, currently a more or less unsolved challenge, were investigated. For this purpose, a small library of phenol-derived chiral phosphane-phosphite ligands containing TADDOL- or BINOL-based phosphite moieties was evaluated. These ligands are easily prepared by a short modular scheme previously developed in this laboratory. Two particularly powerful ligands (4a and 4b, both TADDOL-derived and each possessing a bulky tert-butyl substituent ortho to the phosphite group) were identified. Conditions were optimized with use of the addition of (4-methoxyphenyl)magnesium bromide to cyclohexenone as a standard reaction system. Under optimized conditions [CuBr·SMe 2 (4 mol-%), ligand 4a (6 mol-%), 2-methyl-THF, -78 °C, slow addition of Grignard reagent] the 1,4-product was obtained with high enantioselectivity (up to 95 % ee) and good regioselectivity (r.r. = 90:10). The scope of the method was probed with different aryl-Grignard reagents. It was found that reagents with electron-donating substituents in meta- or para-positions performed particularly well, whereas the presence of F or CF 3 substituents led to decreased ee values. Only ortho-substituted aryl-Grignard reagents did not give rise to useful results. A series of phosphane-phosphite ligands were also tested in the Rh-catalyzed 1,4-addition of phenylboronic acid to cyclohexenone, but enantioselectivities did not exceed 70 % ee in this case. The difficult task of employing aryl-Grignard reagents in Cu-catalyzed enantioselective 1,4 addition reactions was achieved with the assistance of readily accessible chiral modular P,P ligands. High enantioselectivities were obtained in a number of synthetically relevant cases. Copyright
- Naeemi, Qaseem,Dindaroglu, Mehmet,Kranz, Darius P.,Velder, Janna,Schmalz, Hans-Guenther
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experimental part
p. 1179 - 1185
(2012/04/10)
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- Catalytic enantioselective conjugate addition of Grignard reagents to cyclic enones using C1-1,1′-bisisoquinoline-based chiral ligands
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New highly constrained chiral C1-1,1′-bisisoquinoline ligands were examined in the enantioselective conjugate addition of Grignard reagents to cyclohexenone and cyclopentenone. The desired 1,4-adducts were obtained in excellent yield and moderate enantiomeric excess (up to 35%). Copyright Taylor & Francis Group, LLC.
- Qi, Gao,Judeh, Zaher M.A.
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experimental part
p. 1585 - 1592
(2012/05/04)
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- Highly regioselective control of 1,2-addition of organolithiums to α,β-unsaturated compounds promoted by lithium bromide in 2-methyltetrahydrofuran: A facile and eco-friendly access to allylic alcohols and amines
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Very high regioselective 1,2-addition of organolithiums to α,α-unsaturated carbonyl-like compounds (ketones, aldehydes, and imines) in the presence of LiBr was achieved by carrying out reactions in the sustainable solvent 2-methyltetrahydrofuran. Excellent yields (in isolated product) of allylic alcohols and allylic amines were recovered under a simple experimental procedure at 0 °C.
- Pace, Vittorio,Castoldi, Laura,Hoyos, Pilar,Sinisterra, José Vicente,Pregnolato, Massimo,Sánchez-Montero, Ma. José
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supporting information; experimental part
p. 2670 - 2675
(2011/04/23)
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- Syntheses of trans -SCH-A and cis -SCH-A via a stereodivergent cyclopropanation protocol
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(Figure Presented) A highly diastereoselective cyclopropanation protocol has been employed in the syntheses of trans-SCH-A and cis-SCH-A. This strategy encompasses a stereodivergent procedure for the preparation of syn- and anti-cyclopropane diastereoisom
- Csatayova, Kristina,Davies, Stephen G.,Lee, James A.,Ling, Kenneth B.,Roberts, Paul M.,Russell, Angela J.,Thomson, James E.
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supporting information; experimental part
p. 3152 - 3155
(2010/09/05)
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- Enantioselective one-pot conjugate addition of grignard reagents followed by a mannich reaction
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Asymmetric addition of Grignard reagents to cyclohexenone, catalyzed by ferrocene diphosphanes, afforded chiral magnesium enolates. These enolates reacted in a one-pot arrangement with N-benzylidenetoluenesulfonamide to give β-amino carbonyl compounds wit
- Sebesta, Radovan,Bilcik, Filip,Fodran, Peter
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supporting information; experimental part
p. 5666 - 5671
(2011/02/28)
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- Boronic acid catalyzed Friedel-Crafts reactions of allylic alcohols with electron-rich arenes and heteroarenes
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(Chemical Equation Presented) Pentafluorophenylboronic acid catalyzes the regioselective coupling of structurally diverse allylic alcohols with a variety of electron-rich aromatic and heteroaromatic substrates under ambient conditions. The commercially av
- McCubbin, J. Adam,Hosseini, Hamidreza,Krokhin, Oleg V.
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supporting information; experimental part
p. 959 - 962
(2010/04/30)
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- One-pot synthesis of optically active allyl esters via lipase-vanadium combo catalysis
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The combination of vanadium-oxo compounds (3 or 4) with a lipase produced the regio- and enantioconvergent transformation of racemic allyl alcohols (1 or 2) into optically active allyl esters. In this system, the vanadium compounds catalyzed the continuous racemization of the alcohols along with the transposition of the hydroxyl group, while the lipase effected the chemo- and enantioselective esterification to achieve the dynamic kinetic resolution.
- Akai, Shuji,Hanada, Ryosuke,Fujiwara, Noboru,Kita, Yasuyuki,Egi, Masahiro
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supporting information; experimental part
p. 4900 - 4903
(2011/01/12)
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- Copper-catalyzed asymmetric conjugate addition with Grignard reagents and SimplePhos ligands
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Herein we report the copper-catalyzed asymmetric conjugate addition of Grignard reagents to cyclic and acyclic enones, with SimplePhos as chiral ligands. A variety of Grignard reagents can be added to a range of cyclic and acyclic enones, with moderate to good enantioselectivities (ee's up to 86%).
- Palais, Laetitia,Alexakis, Alexandre
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experimental part
p. 2866 - 2870
(2010/04/05)
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- Oxidative rearrangement of tertiary allylic alcohols employing oxoammonium salts
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(Chemical Equation Presented) Practical and highly efficient methods for oxidative rearrangement of tertiary allylic alcohols to β-substituted α,β-unsaturated carbonyl compounds employing oxoammonium salts are described. The methods developed are applicable to acyclic substrates as well as medium membered ring substrates and macrocyclic substrates. The counteranion of the oxoammonium salt plays crucial roles on this oxidative rearrangement.
- Shibuya, Masatoshi,Tomizawa, Masaki,Iwabuchi, Yoshiharu
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p. 4750 - 4752
(2008/09/20)
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- TEMPO/NaIO4-SiO2: A catalytic oxidative rearrangement of tertiary allylic alcohols to β-substituted α,β-unsaturated ketones
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(Chemical Equation Presented) The novel catalytic method for the oxidative rearrangement of tertiary allylic alcohols to β-substituted α,β-unsaturated ketones is described. TEMPO/NaIO4-SiO 2 causes facile and efficient oxidative rearrangement of various acyclic substrates as well as medium-sized and macrocyclic substrates.
- Shibuya, Masatoshi,Tomizawa, Masaki,Iwabuchi, Yoshiharu
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supporting information; experimental part
p. 4715 - 4718
(2009/05/31)
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- Enantioselective Cu-catalyzed 1,4-addition of Grignard reagents to cyclohexenone using Taddol-derived phosphine-phosphite ligands and 2-methyl-THF as a solvent
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A small library of modular P,P ligands was screened and a potent Cu-based catalyst system was identified for highly enantioselective 1,4-additions to cyclohexenone with an unprecedented broad spectrum of Grignard reagents. Surprisingly, the highest selectivities were achieved in most cases in 2-methyl-THF, a green solvent underestimated so far.
- Robert, Tobias,Velder, Janna,Schmalz, Hans-Guenther
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supporting information; experimental part
p. 7718 - 7721
(2009/04/10)
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- Unusual dimerization of N-protected bromomethylindoles/benzyl bromide with arylmetal halides: generation of indolylmethyl/benzyl radical
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A detailed study on the interaction of N-protected bromomethylindoles with various types of aryl/alkyl Grignard is reported. Full experimental details on the mechanism of the unusual dimerization reaction are presented.
- Ramesh, Neelamegam,Prakash, Chandran,Sureshbabu, Radhakrishnan,Dhayalan, Vasudevan,Mohanakrishnan, Arasambattu K.
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p. 2071 - 2079
(2008/09/17)
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- Oxidative rearrangement of cyclic tertiary allylic alcohols with IBX in DMSO
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(Chemical Equation Presented) A practical and environmentally friendly method for oxidative rearrangement of five- and six-membered cyclic tertiary allylic alcohols to β-disubstituted α,β-unsaturated ketones by the IBX/DMSO reagent system is described. Several conventional protecting groups (e.g., Ac, MOM, and TBDPS) are compatible under the reaction conditions prescribed.
- Shibuya, Masatoshi,Ito, Shinichiro,Takahashi, Michiyasu,Iwabuchi, Yoshiharu
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p. 4303 - 4306
(2007/10/03)
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- Effect of InCl3 on the addition of Grignard reagents to α,β-unsaturated carbonyl compounds
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Control of 1,2- versus 1,4-addition of organometallic reagents to enones remains a long-standing problem. There is still no satisfactory 1,2-directing agent comparable to the 1,4-directing effect of copper salts. We report that the presence of just 5 mol% indium(III) chloride can significantly alter the amount of 1,2-product formed in these reactions.
- Kelly, Brian G.,Gilheany, Declan G.
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p. 887 - 890
(2007/10/03)
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- 1,4-Addition of diorganozincs to α,β-unsaturated ketones catalyzed by a copper(I)-sulfonamide combined system
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A mixture of CuCN and N-benzylbenzenesulfonamide catalyzes the 1,4- addition of dialkylzincs or diarylzincs (Cu: Zn = 1: 200 to 1: 10000) to α,β-unsaturated ketones to give, after aqueous workup, the corresponding β-substituted ketones in nearly quantitative yields. A range of cyclic enones having s-cis or s-trans geometries as well as conformationally flexible acyclic enones are usable as substrates. The ethyl group migrates more readily than the methyl and phenyl groups. CuOTf, CuO-t-C4H9, and mesitylcopper can be used in place of CuCN. The in situ-formed alkylzinc enolate, prior to aqueous workup, further undergoes an aldol reaction with aldehydes or Pd(0)-assisted coupling with allyl acetate, resulting in regio- controlled, vicinal carbacondensation products. A catalytic cycle is proposed on the basis of a kinetic study and a structural analysis of the zinc enolate product by NMR and molecular weight measurements.
- Kitamura, Masato,Miki, Takashi,Nakano, Keiji,Noyori, Ryoji
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p. 999 - 1014
(2007/10/03)
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- 71. Enantioselective Copper-Catalyzed 1,4-Addition of Grignard Reagents to α,β-Unsaturated Carbonyl Compounds
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The enantioselective copper-catalyzed 1,4-addition of Grignard reagents to α,β-unsaturated carbonyl compounds was studied with the following Cu(I) compounds as catalyst precursor and 1,2:5,6-di-O-isopropylidene-3-thio-α-D-glucofuranose (Hsiig) as chiral l
- Spescha, Maurus,Rihs, Grety
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p. 1219 - 1230
(2007/10/02)
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- Ultrasound Assisted Preparation of Organocerium Reagents
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Sonication of anhydrous CeCl3 in tetrahydrofuran facilitates rapid preparation of organocerium reagents.
- Greeves, Nicholas,Lyford, Lisa
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p. 4759 - 4760
(2007/10/02)
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- Mechanism of the Grignard Adddition Reaction. XVI. Homolytic and Concerted Mechanisms in the Reaction of α,β-Unsatureted Carbonyl Compounds with Grignard Reagents
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Kinetic measurements have shown that the addition of Grignard reagents to α,β-unsaturated carbonyl compounds takes place either by a concerted mechanism or by a homolytic mechanism.Phenylmagnesium bromide, which is incapable of homolysis, reacts rapidly in a 1,4-fashion if an s-cis conformation exists between the C=C and the C=O bonds, but only 1,2-addition takes place if the conformation is s-trans.tert-Butylmagnesium bromide is unsuited to the concerted reaction, but 1,4-addition takes place via homolysis.Primary and secondary Grignard reagents, like phenyl, react rapidly in a concerted manner with s-cis substrates, but unlike phenyl, these Grignard reagents may, with s-trans substrates, produce some 1,4-adduct via the homolytic mechanism.
- Holm, Torkil
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p. 925 - 929
(2007/10/02)
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- Reactions of Carbonyl Compounds with Grignard Reagents in the Presence of Cerium Chloride
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The addition of Grignard reagents to ketones is significantly enhanced by cerium chloride with remarkable supression of side reactions, particularly enolization.Some esters, which are prone to side reactions, also react readily with Grignard reagents in the presence of cerium chloride to give normal reaction products in reasonable to high yields.
- Imamoto, Tsuneo,Takiyama, Noboyuki,Nakamura, Kimikazu,Hatajima, Toshihiko,Kamiya, Yasuo
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p. 4392 - 4398
(2007/10/02)
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- THE PREPARATION OF LITHIUM ORGANOCUPRATES FROM VARIOUS Cu(I) SALTS
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Various Cu(I) salts have been tested as precursors for organocuprates in side-by-side comparisons under controlled conditions.CuCN and CuBr*SMe2 appear to be superior to CuI, CuBr, and CuCl.CuSCN and CuOTf are also good precursors in some circumstances.
- Bertz, Steven H.,Gibson, Charles P.,Dabbagh, Gary
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p. 4251 - 4254
(2007/10/02)
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- Regioselective 1,4-Addition to α,β-Unsaturated Ketones with Grignard Reagents Mediated by (N,N,N',N'-Tetramethylethylenediamine)zinc(II) Chloride
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The reaction of α,β-unsaturated ketones with a THF solution RMgX (3 mol equiv) and ZnCl2*TMEDA (1 mol equiv) followed by NH4Cl gave 1,4-addition products.The products were contaminated by 1,2-addition products when R = Ph and Me but were essentially free of those compounds when R = n-Bu or i-Pr.The yields were highest when X = Cl.Thus the reaction of 2-cyclohexen-1-one with a solution of n-BuMgCl and ZnCl2*TMEDA gave 3-n-butylcyclohexanone (1) in 96percent yield.
- Kjonaas, Richard A.,Vawter, Edward J.
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p. 3993 - 3996
(2007/10/02)
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