- Indium-promoted preparation of substituted α-methylene-γ-lactones from 2-(bromomethyl)acrylic acid and carbonyl compounds
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The reaction of 2-(bromomethyl)acrylic acid (1) with different carbonyl compounds (2) [CH20, (E)-CH3CH=CHCHO, Pr(i)CHO, Bu(t)CHO, PhCHO, CH3(CH2)5CHO, c-C6H11CHO, Ph2CHCHO, (CH2)5CO] and indium powder in a 1:1 THF:H20 mixture at room temperature affords, after acidic work-up with hydrochloric acid, the corresponding α-methylene-γ-butyrolactones 3.
- Choudhury, Prabir K.,Foubelo, Francisco,Yus, Miguel
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- Efficient and connective synthesis of substituted butyrolactones and exo-methylene butyrolactones
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A variety of α-(trimethylsilylmethyl)-substituted butyrolactones are readily accessed by a novel tandem ene-reaction/oxidative desilylation of a range of aldehydes. Subsequent functionalisation led to an efficient methodology for the preparation of exo-methylene butyrolactones. (C) 2000 Published by Elsevier Science Ltd.
- Leroy, Bernard,Dumeunier, Rapha?l,Markó, István E.
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Read Online
- Dibromomethane as one-carbon source in organic synthesis: A versatile methodology to prepare the cyclic and acyclic α-methylene or α-keto acid derivatives from the corresponding terminal alkenes
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Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH2Br2-Et2NH affords α-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A-2 can be easily converted to α-methylene esters A-4, which could be further converted to the corresponding α-keto esters A-5. This methodology can be also applied to the preparation of α-methylene lactones B-4, α-methylene lactams, and α-keto lactones B-5 with various ring sizes.
- Hon, Yung-Son,Liu, Yu-Wei,Hsieh, Cheng-Han
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p. 4837 - 4860
(2007/10/03)
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- Concise and connective synthesis of exo-methylene-γ-butyrolactones
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A novel sequence, combining an ene-reaction of the substituted allylsilane 2 with a variety of aldehydes, followed by an oxidative double desilylation, provides an efficient access to a wide range of exo-methylene-γ-butyrolactones.
- Dumeunier, Rapha?l,Leclercq, Cédric,Markó, István E
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p. 2307 - 2311
(2007/10/03)
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- Tandem ene-reaction/Intramolecular Sakurai Cyclisation (IMSC): A novel access to polysubstituted tetrahydropyrans and γ-butyrolactones using a unique allylation strategy
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The ene-reaction between a variety of aldehydes and allylsilane 22 generates highly functionalised homoallylic alcohols 23. These adducts undergo a subsequent Intramolecular Sakurai Cyclisation (IMSC), affording in good yields polysubstituted tetrahydropyran derivatives. Furthermore, oxidative desilylation of 23 provides an efficient, connective access to a range of γ-butyrolactones and α-methylene-γ-butyrolactones.
- Marko, Istvan E.,Dumeunier, Raphael,Leclercq, Cedric,Leroy, Bernard,Plancher, Jean-Marc,Mekhalfia, Abdelaziz,Bayston, Daniel J.
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p. 958 - 972
(2007/10/03)
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- Direct indium-promoted preparation of α-methylene-γ-lactones from 2- (bromomethyl)acrylic acid and carbonyl compounds
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The reaction of 2-(bromomethyl)acrylic acid (2) with different carbonyl compounds 1 [CH2O, (E)-CH3CH=CHCHO, (i)PrCHO, (t)BuCHO, PhCHO, CH3(CH2)5CHO, c-C6H11CHO, Ph2CHCHO, (CH2)5CO, furfural, 1,4- cyclohexanedione, 2-chlorocyclohexanone, 2-hydroxybenzaldehyde, phthaldehyde, N-Boc-3-indolecarboxaldehyde, cholestanone, (1R)-(-)-myrtenal] and indium powder in a 1:1 THF:H2O mixture at room temperature affords, after acidic work-up with 6M hydrochloric acid, the corresponding α-methylene-γ-lactones 3.
- Choudhury, Prabir K.,Foubelo, Francisco,Yus, Miguel
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p. 10779 - 10788
(2007/10/03)
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- Catalytic acryloxypalladation of vinylcycloalkanes and exo-methylene cycloalkanes. Mechanistic insights into the competition between allylic acryloxypalladation and formation of a-methylene y-butyrolactones
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Acryloxypalladation of ezo-methylenecycloalkanes (three-, four-, five- and six-membered rings) and vinylcycloalkanes (three-, five- and six-membered rings) in the presence of the Pd(OAc)2/p-benzoquinone/MnC>2 catalytic system is reported. Except for the case of eio-methylenecyclopropane, this reaction provides a rapid entry to the corresponding Q-metliylene -/-butyrolactone, which essentially results from a 1,2-Markovnikov acryloxypalladation addition on the double bond. The subsequent insertion of the acrylate double bond into the carbon-palladium bond is followed by a β-elimination step. However, this reaction competes with the formation of intermediate -allyl complexes which yields the corresponding allylic acrylates. The ratio of butyrolactones to allylic acrylates is dependent on ring size. Elsevier,.
- Ferret, Nicolas,Mussate-Mathieu, Laurence,Perfetti, Patricia,Zahra, Jean-Pierre,Waegell, Bernard
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p. 1023 - 1031
(2007/10/03)
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- Palladium-catalyzed carbonyl allylation by 2-(hydroxymethyl)acrylate derivatives: Synthesis of α-methylene-γ-butyrolactones
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Ethyl 2-(hydroxymethyl)acrylate derivatives serve as reagents for 2-ethoxycarnonylallylation of carbonyl compounds using PdCl2(PhCN)2-SnCl2 system to produce α-methylene-γ-butyrolactones diastereoselectively.
- Masuyama,Nimura,Kurusu
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p. 225 - 228
(2007/10/02)
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- Asymmetric Synthesis of α-Methylene-γ-butyrolactones Using Chiral N-Monosubstituted 2-propenamides
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α-Methylene-γ-butyrolactones were prepared in high yields on treatment of N-monosubstituted 2-propenamides with aldehydes in the presence of a Lewis acid followed by acidic hydrolysis of the resulting γ-hydroxy amides.Asymmetric synthesis of α-methylene-γ-butyrolactones was investigated by using a variety of chiral 2-propenamides derived from optically active amines.Reaction of N--2-propenamide or its antipode with aldehydes in the presence of 4 equiv of TiCl4 gave, after hydrolysis, α-methylene lactones in an enantiometric excess of as high as 80percent.Optically pure 3-methylene-2-pyrrolidinones were obtained in excellent yields by a one-pot sequence starting with the γ-hydroxy amides.
- Tanaka, Kazuhiko,Yoda, Hidemi,Isobe, Yutaka,Kaji, Aritsune
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p. 1856 - 1866
(2007/10/02)
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- DIANION OF N-(o-METHOXYPHENYL)-2-METHYLPROPENAMIDE: A NEW REAGENT FOR THE CONVENIENT SYNTHESIS OF α-METHYLENE-γ-BUTYROLACTONES FROM CARBONYL COMPOUNDS
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Dianion of N-(o-methoxyphenyl)-2-methylpropenamide was successfully generated on treatment of the amide with t-BuOK-BuLi at -78 degC in THF and utilized as the key reagent for the synthesis of γ-substituted α-methylene-γ-butyrolactones.
- Tanaka, Kazuhiko,Nozaki, Yoshihito,Tamura, Norikazu,Tanikaga, Rikuhei,Kaji, Aritsune
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p. 1567 - 1568
(2007/10/02)
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