- Asymmetric synthesis of α-acyl-γ-butyrolactones possessing all-carbon quaternary stereocenters by phase-transfer-catalyzed alkylation
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The enantioselective construction of all-carbon quaternary stereocenters on α-acyl-γ-butyrolactones has been achieved by the N-spiro chiral quaternary ammonium bromide 1-catalyzed alkylation under mild phase-transfer conditions. The resulting α-alkylated
- Ooi, Takashi,Miki, Takashi,Fukumoto, Kazuhiro,Maruoka, Keiji
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- α-Amino-α-vinyl-γ-butyrolactone derivatives from α-{[(trimethylsilyl)-methyl]alkylidene}-γ-butyrolactones
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N-Protected α-amino-α-vinyl-γ-butyrolactones 1 are obtained by the aza-Michael-type addition of NsONHCO2Et to novel silylated α-ylidene-γ-butyrolactones 2, through ring opening of the intermediate aziridine and loss of the trimethylsilyl group.
- Capuzzi, Marinella,Gambacorta, Augusto,Gasperi, Tecla,Loreto, M. Antonietta,Tardella, P. Antonio
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- Br?nsted Acid-Catalyzed Carbonyl-Olefin Metathesis inside a Self-Assembled Supramolecular Host
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Carbonyl–olefin metathesis represents a powerful yet underdeveloped method for the formation of carbon–carbon bonds. So far, no Br?nsted acid based method for the catalytic carbonyl–olefin metathesis has been described. Herein, a cocatalytic system based on a simple Br?nsted acid (HCl) and a self-assembled supramolecular host is presented. The developed system compares well with the current benchmark catalyst for carbonyl–olefin metathesis in terms of substrate scope and yield of isolated product. Control experiments provide strong evidence that the reaction proceeds inside the cavity of the supramolecular host. A mechanistic probe indicates that a stepwise reaction mechanism is likely.
- Catti, Lorenzo,Tiefenbacher, Konrad
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supporting information
p. 14589 - 14592
(2018/01/27)
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- A palladium-catalyzed asymmetric allylic alkylation approach to α-quaternary γ-butyrolactones
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The Pd-catalyzed asymmetric allylic alkylation (Pd-AAA) of enol carbonates derived from γ-butyrolactones is reported, affording the corresponding enantioenriched α,α′-disubstituted γ-butyrolactones in both high yields and high enantioselectivities (up to 94% ee). This method was eventually applied to the synthesis of chiral spirocyclic compounds.
- De Oliveira, Marllon Nascimento,Fournier, Jeremy,Arseniyadis, Stellios,Cossy, Janine
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supporting information
p. 14 - 17
(2017/11/27)
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- Reductive Reformatsky-Honda reaction of α,β-unsaturated esters: Facile formation of 1,3-dicarbonyl compounds and β-hydroxy esters
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The reaction of tris(triphenylphosphine)rhodium chloride [RhCl(PPh 3)3] with diethylzinc (Et2Zn) easily afforded a rhodium-hydride complex that effects the 1,4-reduction of α,β- unsaturated esters to give rhodium enolates. Formation of the rhodium enolate is followed by transmetalation with the zinc species to give a Reformatsky-type reagent, and this reacts with various acid chlorides at the α-position to give β-keto esters. The Reformatsky-type reagent also reacts with various electrophiles such as aldehydes, ketones and acid anhydrides to give the corresponding products in which the electrophiles were introduced reductively at the α-position of α,β-unsaturated esters. Copyright
- Sato, Kazuyuki,Isoda, Motoyuki,Ohata, Shizuka,Morita, Shuhei,Tarui, Atsushi,Omote, Masaaki,Kumadaki, Itsumaro,Ando, Akira
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supporting information; experimental part
p. 510 - 514
(2012/04/23)
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- Substrate range of the titanium TADDOLate catalyzed asymmetric fluorination of activated carbonyl compounds
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The substrate range of the [TiCl2(TADDOLate)] (TADDOL=α,α,α′,α′-tetraaryl-1,3-dioxolane-4, 5-dimethanol)-catalyzed asymmetric α-fluorination of activated β-carbonyl compounds has been investigated. Optimal conditions for catalysis are characterized by using 5 mol-% of TiCl2(naphthalen-1- yl)-TADDOLate) as catalyst in a saturated (0.14 mol/l) MeCN solution of F-TEDA (1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis- [tetrafluoroborate]) at room temperature. A series of α-methylated β-keto esters (3-oxobutanoates, 3-oxopentanoates) with bulky benzyl ester groups (60-90% ee) or phenyl ester (67-88% ee) have been fluorinated readily, whereas α-acyl lactones were also readily fluorinated, but gave lower inductions (13-46% ee). Double stereochemical differentiation in β-keto esters with chiral ester groups raised the stereoselectivity to a diastereomeric ratio (dr) of up to 96.5:3.5. For the first time, β-keto S-thioesters were asymmetrically fluorinated (62-91.5% ee) and chlorinated (83% ee). Lower inductions were observed in fluorinations of 1,3-diketones (up to 40% ee) and β-keto amides (up to 59% ee). General strategies for preparing activated β-carbonyl compounds as important model substrates for asymmetric catalytic α-functionalizations are presented (>60 examples). Copyright
- Bertogg, Andreas,Hintermann, Lukas,Huber, Dominique P.,Perseghini, Mauro,Sanna, Maria,Togni, Antonio
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experimental part
p. 353 - 403
(2012/05/07)
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- Formal [4+1] annulation of cyclopropyl amides and water mediated by Lewis acid: A novel entry to γ-butyrolactones
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An efficient one-pot synthesis of substituted -butyrolactones from cyclopropyl amides mediated by the Lewis acid SnClH is reported. A mechanism involving a tandem ring-opening reaction and intramolecular cyclization reaction is proposed. Georg Thieme Verlag Stuttgart · New York.
- Zhang, Dingyuan,Zhang, Rui,Liang, Yongjiu,Dong, Dewen
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experimental part
p. 1679 - 1685
(2012/07/03)
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- Highly diastereo- and enantioselective Mannich reaction of lactones with N-Boc-aldimines catalyzed by bifunctional rosin-derived amine thiourea catalysts
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A highly efficient diastereo- and enantioselective Mannich reaction of lactones with a variety of N-Boc-aldimines by using bifunctional rosin-derived amine thiourea catalysts was investigated for the first time, in general, affording the adducts bearing q
- Jiang, Xianxing,Fu, Dan,Zhang, Gen,Cao, Yiming,Liu, Luping,Song, Jingjing,Wang, Rui
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supporting information; experimental part
p. 4294 - 4296
(2010/08/07)
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- Oxidation products of 2-acyl-4,5-dihydrofurans
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2-Benzoyl-4,5-dihydrofuran (5) readily undergoes oxidation in air, during chromatography on silica, or following exposure to oxidising agents (MCPBA, DMDO), to give 2-benzoylbutyrolactone (6) and tricycle 7 as the major products.
- Robertson, Jeremy,Tyrrell, Andrew J.,Skerratt, Sarah
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p. 6285 - 6287
(2007/10/03)
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- Unexpected reaction of a dimethylzinc-generated THF radical with aldehydes
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A dimethylzinc-air-generated THF radical reacted with aldehydes at the β-position of an α-oxygenated THF.
- Yamamoto, Yasutomo,Yamada, Ken-Ichi,Tomioka, Kiyoshi
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p. 795 - 797
(2007/10/03)
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- Preparation of organomanganese reagents from organic halides with activated manganese
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Reduction of Li2MnCl4 with magnesium metal provided activated manganese as a black suspension in THF. Treatment of organic halides such as allyl bromides, α-halo esters or aryl halides with activated manganese furnished various organomanganese reagents which reacted further with electrophiles to afford the corresponding adducts. The reaction of a ketone bearing an iodoaryl moiety with this active manganese induced cyclization to provide dihydroindene derivative.
- Kakiya, Hirotada,Nishimae, Shinji,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 8807 - 8815
(2007/10/03)
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- THE SELECTIVE CLAISEN AND DIECKMANN ESTER CONDENSATION PROMOTED BY DICHLOROBIS(TRIFLUOROMETHANESULFONATO)TITANIUM(IV)
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Inter and intramolecular condensations (the Claisen and the Dieckmann condensations) between ester functions have been performed by the combined use of dichlorobis(trifluoromethanesulfonato)titanium(IV) (=dichlorobis(triflato)titanium(IV)) and tertiary amine under mild reaction conditions.These results led to the development of the selective (crossed) Claisen and Dieckmann ester condensation between methoxymethyl ester and methyl ester, in that, dichlorobis(triflato)titanum(IV) contribute to control the direction of the reaction.
- Tanabe, Yoo
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p. 1917 - 1924
(2007/10/02)
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- DICHLORO-BIS(TRIFLUOROMETHANESULFONATO)TITANIUM(IV) AS AN EFFECTIVE PROMOTER IN THE CLAISEN ESTER CONDENSATION
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Inter- and intra-molecular condensation (the Claisen and the Dieckmann condensations) between ester functions have been effected by the combined use of dichloro-bis(trifluoromethanesulfonato)titanium(IV) and tertiary amine under mild conditions.
- Tanabe, Yoo,Mukaiyama, Teruaki
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p. 1867 - 1870
(2007/10/02)
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- "Wolf and lamb" reactions: Equilibrium and kinetic effects in multipolymer systems
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Two reagents reacting avidly with each other in solution are rendered mutually inactive by attaching each to a separate batch of insoluble polymer. Two-stage reactions in which a soluble reagent reacts first with one polymeric reagent and the product with the second polymeric reagent afford advantages over analogous reactions in solution. In acylation reactions of carbon acids, the simultaneous use of a polymeric strong base and a polymeric acylating reagent proved to be superior to the use of soluble reagents, both for bringing about quantitative acylations and for coping with undesirable side reactions. New polymeric strong bases were prepared: polymeric trityllithium, para-substituted trityllithium polymers, and polymeric lithium diisopropylamide. Active esters of polymeric o-nitrophenol and N-1-hydroxybenzotriazole were used as acylation reagents. The scope and limitation of these reactions and their application to general multiphase systems are discussed.
- Cohen,Kraus,Patchornik
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p. 7620 - 7629
(2007/10/02)
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