- Lipase-catalyzed domino dynamic kinetic resolution of racemic 3-vinylcyclohex-2-en-1-ols/intramolecular diels-alder reaction: One-pot synthesis of optically active polysubstituted decalins
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Combining chemistry: The use of a lipase and a ruthenium catalyst allows the direct preparation of polysubstituted decalines with high optical and chemical yields from racemic alcohols (see scheme). The lipase-catalyzed kinetic resolution of the racemic alcohols, the ruthenium-catalyzed racemization of the slow-reacting enantiomers, and an intramolecular Diels-Alder reaction of the resultant esters all occur under identical conditions.
- Akai, Shuji,Tanimoto, Kouichi,Kita, Yasuyuki
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- Four-Step One-Pot Catalytic Asymmetric Synthesis of Polysubstituted Tricyclic Compounds: Lipase-Catalyzed Dynamic Kinetic Resolution Followed by an Intramolecular Diels-Alder Reaction
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Starting from readily available tertiary alcohols, four different reactions (a 1,3-migration of a hydroxy group, kinetic resolution, racemization, and an intramolecular Diels-Alder reaction) took place under co-catalysis by lipase and oxovanadium compounds in a one-pot process to produce polysubstituted tricyclic carbon frameworks in high yields and with high enantioselectivities. The key to the success of this process was the discovery that a silyl group attached to the terminal carbon of the vinyl moiety completely controls the direction of hydroxy group migration.
- Tsuchimochi, Izuru,Hori, Shuhei,Takeuchi, Yasuo,Egi, Masahiro,Satoh, Tomo-O,Kanomata, Kyohei,Ikawa, Takashi,Akai, Shuji
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p. 822 - 828
(2021/02/16)
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- Two-Phase Synthesis of Taxol
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Taxol (a brand name for paclitaxel) is widely regarded as among the most famed natural isolates ever discovered, and has been the subject of innumerable studies in both basic and applied science. Its documented success as an anticancer agent, coupled with early concerns over supply, stimulated a furious worldwide effort from chemists to provide a solution for its preparation through total synthesis. Those pioneering studies proved the feasibility of retrosynthetically guided access to synthetic Taxol, albeit in minute quantities and with enormous effort. In practice, all medicinal chemistry efforts and eventual commercialization have relied upon natural (plant material) or biosynthetically derived (synthetic biology) supplies. Here we show how a complementary divergent synthetic approach that is holistically patterned off of biosynthetic machinery for terpene synthesis can be used to arrive at Taxol.
- Kanda, Yuzuru,Nakamura, Hugh,Umemiya, Shigenobu,Puthukanoori, Ravi Kumar,Murthy Appala, Venkata Ramana,Gaddamanugu, Gopi Krishna,Paraselli, Bheema Rao,Baran, Phil S.
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supporting information
p. 10526 - 10533
(2020/07/27)
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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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p. 3677 - 3686
(2018/06/04)
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- A highly efficient metal-free approach to: Meta - And multiple-substituted phenols via a simple oxidation of cyclohexenones
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A novel and efficient metal-free approach to substituted phenols has been disclosed from simple and readily available cyclohexenones and cyclohexenone equivalents. Dimethyl sulfoxide (DMSO), a simple and common organic reagent, was employed as a mild oxidant in this I2-catalysis, which significantly tolerates various substituents including some easily oxidizable or reducible functionalities. The challenging meta- and multiple-substituted phenols could be well prepared by this method. The metal-free and mild oxidation make this protocol very simple, practical, and easy to handle.
- Liang, Yu-Feng,Song, Song,Ai, Lingsheng,Li, Xinwei,Jiao, Ning
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supporting information
p. 6462 - 6467
(2018/06/08)
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- Route optimization and synthesis of taxadienone
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Early process development toward the scalable production of taxadienone on a decagram scale is described. A continuous flow reactor was employed to safely run a potentially hazardous cyclopropane ring opening. The route featured two copper-mediated additions, a Diels-Alder reaction and a palladium-catalyzed Negishi coupling, to construct the final structure.
- Krasutsky, Sergiy G.,Jacobo, Sheila H.,Tweedie, Scott R.,Krishnamoorthy, Ravi,Filatov, Alexander S.
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p. 284 - 289
(2015/01/30)
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- Diels-Alder reactions of masked o-benzoquinones with 1-vinylcyclohexenes: A short and efficient entry to highly functionalized decahydrophenanthrene skeleton
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Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding cycloaddition products, that is, decahydrophenanthrenes along with bicyclo[2.2.2]octenones. In the former case, the MOBs serve as the dienophile, and in the later case, the 1-vinylcyclohexenes act as the dienophile. The obtained bicyclo[2.2.2]octenones could be transformed into the corresponding decahydrophenanthrenes through a Cope rearrangement at 220 °C. Thus, these tandem reactions provide a short and efficient entry to the decahydrophenanthrene skeleton from easily available 2-methoxyphenols. Masked o-benzoquinones (MOBs), which were generated in situ from 2-methoxyphenols, underwent Diels-Alder reactions with 1-vinylcyclohexenes to produce the corresponding decahydrophenanthrenes and bicyclo[2.2.2]octenones. The obtained bicyclo[2.2.2]octenones could be transformed into decahydrophenanthrenes through a Cope rearrangement at 220 °C. Copyright
- Niu, Guang-Hao,Hou, Chieh-Shen,Chuang, Gary Jing,Wu, Chi-Phi,Liao, Chun-Chen
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p. 3794 - 3801
(2014/06/24)
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- The cinchona primary amine-catalyzed asymmetric epoxidation and hydroperoxidation of α,β-unsaturated carbonyl compounds with hydrogen peroxide
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Using cinchona alkaloid-derived primary amines as catalysts and aqueous hydrogen peroxide as the oxidant, we have developed highly enantioselective Weitz-Scheffer-type epoxidation and hydroperoxidation reactions of α,β-unsaturated carbonyl compounds (up to 99.5:0.5 er). In this article, we present our full studies on this family of reactions, employing acyclic enones, 5-15-membered cyclic enones, and α-branched enals as substrates. In addition to an expanded scope, synthetic applications of the products are presented. We also report detailed mechanistic investigations of the catalytic intermediates, structure-activity relationships of the cinchona amine catalyst, and rationalization of the absolute stereoselectivity by NMR spectroscopic studies and DFT calculations.
- Lifchits, Olga,Mahlau, Manuel,Reisinger, Corinna M.,Lee, Anna,Fares, Christophe,Polyak, Iakov,Gopakumar, Gopinadhanpillai,Thiel, Walter,List, Benjamin
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supporting information
p. 6677 - 6693
(2013/06/05)
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- Oxidative conversion of silyl enol ethers to α,β-unsaturated ketones employing oxoammonium salts
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The oxidative conversion of silyl enol ethers to α,β-unsaturated ketones using a less-hindered class of oxoammonium salts (AZADO +BF4-) is described. The reaction proceeds via the ene-like addition of oxoammonium salts to silyl enol ethers.
- Hayashi, Masaki,Shibuya, Masatoshi,Iwabuchi, Yoshiharu
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supporting information; experimental part
p. 154 - 157
(2012/02/16)
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- Unexpected regiospecific reactivity of a substituted phthalic anhydride
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Regioselective nucleophilic addition at C1 of anhydride 7 by a range of nucleophiles occurs to produce amide, ester and thioester derivatives 8-15 (60-99%). The increased electrophilic reactivity of the C1 carbonyl group of anhydride 7 is supported by a competition experiment with phthalic anhydride. Unexpected formation of lactams 18 and 19 from amides 12 and 13 was shown to proceed via the lactamols 16 and 17 and could be controlled by the reaction conditions. The solid-state structure of 19 is reported.
- Petersson, Maria J.,Marchal, Camille,Loughlin, Wendy A.,Jenkins, Ian D.,Healy, Peter C.,Almes?ker, Ann
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p. 1395 - 1401
(2007/10/03)
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- Organocatalytic asymmetric 1,6-additions of β-ketoesters and glycine imine
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The first organocatalytic enantioselective 1,6-addition of β-ketoesters and benzophenone imine to electron-poor δ-unsubstituted dienes using cinchona alkaloids under phase-transfer conditions is demonstrated. The scope of the reaction for the β-ketoesters
- Bernardi, Luca,Lopez-Cantarero, Jesus,Niess, Barbara,Jorgensen, Karl Anker
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p. 5772 - 5778
(2008/02/04)
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- Highly stereoselective hydroxy-directed Diels-Alder reaction
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The successful stereocontrol of the Diels-Alder reaction of semicyclic dienes possessing a secondary and tertiary allylic magnesium alkoxide alcohol functionality and activated dienophiles such as methyl acrylate, methacrolein, acrolein, and N-phenylmalei
- Barriault, Louis,Thomas, Jermaine D. O.,Clement, Roxanne
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p. 2317 - 2323
(2007/10/03)
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- Generation of α-alkylthio radicals by photoinduced one-electron oxidation of α-stannyl sulfides and their use for carbon-carbon bond formation
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Cation radicals, generated from α-stannyl sulfides by the photoinduced single electron transfer, cleave into α-alkylthio radical intermediates with the elimination of the stannyl group. The α-alkylthio radicals thus formed are utilized for carbon-carbon b
- Ikeno, Taketo,Harada, Manabu,Arai, Noriyoshi,Narasaka, Koichi
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p. 169 - 170
(2007/10/03)
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- Two methods for the preparation of 2-cyclohexenones from resin-bound 1,3-cyclohexanedione
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The addition of organolithium or Grignard reagents to viny]ogous ester resin 1 followed by mild hydrolysis of product resins 2 provides 3-alkyl-2-cyclohexenones in high purity (>95%). Alternatively, conversion of 1 to vinyl triflate resin 4 followed by palladium-mediated couplings with aryl boronic acids and hydrolysis furnishes 3-ary]-2-cyclohexenones in lower yield, but exceptional purity.
- Fraley, Mark E.,Rubino, Robert S.
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p. 3365 - 3368
(2007/10/03)
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- Palladium(II)-Catalyzed Coupling of 2-Carboxyethyl Enol Triflates with Organostannanes
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Enol triflates 1-5, derived from the corresponding dicarbonyl compound, were coupled with tin reagents 6-8 using Pd(OAc)2 and PPh3 as the catalyst, at 7 mole percent, in 56-91percent yield.
- Houpis, Ioannis N.
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p. 6675 - 6678
(2007/10/02)
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- 1,3-Oxidative Rearrangements of Dienols
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Oxidation of 1-vinyl-2-cycloalken-1-ols with PDC regiospecifically affords conjugated dienones in moderate to good yields.
- Majetich, George,Condon, Stephen,Hull, Kenneth,Ahmad, Saeed
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p. 1033 - 1036
(2007/10/02)
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