- One-pot vinylogous aldol addition of β,γ-unsaturated esters under mild conditions
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We described a one-pot vinylogous aldol addition of methyl 3-butenoate to aromatic aldehydes in the presence of silver salts and the TMSCl-TBAF mixture. The reaction can be done simply by sequentially mixing reagents in situ, and it does not require any c
- Ak?ok, Ismail,?a?ir, Ali
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- Enzyme mediated kinetic resolution of δ-hydroxy-α,β-unsaturated esters as a route to optically active δ-lactones
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A novel synthetic route to optically active saturated and unsaturated δ-lactones based on enzymatic kinetic resolution and ring-closing metathesis reactions has been proposed. The influence of temperature, co-solvent, organic additives and the substrate s
- Koszelewski, Dominik,Paprocki, Daniel,Brodzka, Anna,Ostaszewski, Ryszard
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p. 809 - 818
(2017/06/13)
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- Diastereoselective synthesis of trifluoromethylated 1,3-dioxanes by intramolecular oxa-Michael reaction
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A highly diastereoselective synthesis of trifluoromethylated 1,3-dioxanes is described. The reaction proceeds by an addition/oxa-Michael sequence and works efficiently under mild reaction conditions, with a good substrate scope and acceptable to good yiel
- Becerra-Figueroa, Liliana,Brun, Elodie,Mathieson, Michael,Farrugia, Louis J.,Wilson, Claire,Prunet, Jo?lle,Gamba-Sánchez, Diego
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p. 301 - 305
(2017/01/13)
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- The vinylogous aldol reaction of unsaturated esters and enolizable aldehydes using the novel Lewis acid aluminum tris(2,6-di-2-naphthylphenoxide)
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The synthesis of the novel Lewis acid, aluminum tris(2,6-di-2- naphthylphenoxide) (ATNP), and its use in the vinylogous aldol reaction between methyl crotonate and enolizable aldehydes are described. ATNP is related to Yamamoto's Lewis acid, aluminum tris(2,6-diphenylphenoxide) (ATPH), but the 2-naphthyl groups more effectively block the α-position of aldehydes, enabling the selective enolization of crotonate esters in the presence of enolizable aldehydes. Vinylogous aldol reactions then proceed smoothly and in high yields with a variety of substrates.
- Gazaille, Jeffrey A.,Sammakia, Tarek
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supporting information; experimental part
p. 2678 - 2681
(2012/07/28)
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- Enantioselective syntheses of cryptocarya triacetate, Cryptocaryolone, and cryptocaryolone diacetate
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(Matrix presented) The enantioselective syntheses of three natural products from Cryptocarya latifolia have been achieved in 13-15 steps from ethyl sorbate. The route relies upon an enantio- and regioselective Sharpless dihydroxylation and a palladium-cat
- Smith, Catherine M.,O'Doherty, George A.
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p. 1959 - 1962
(2007/10/03)
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- Molecular recognition of α,β-unsaturated carbonyl compounds using aluminum tris(2,6-diphenylphenoxide) (ATPH): Structural and conformational analysis of ATPH complexes and application to the selective vinylogous aldol reaction
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Various α,β-unsaturated carbonyl compounds were coordinated with aluminum tris(2,6-diphenylphenoxide) (ATPH) to give the corresponding Lewis acid-base complexes in a distinctive coordination fashion (selective coordination). ATPH recognizes carbonyl substrates and subsequently orients itself as it forms a stable complex through selective coordination with the carbonyl oxygen. Selective coordination also confers a conformational preference to each carbonyl compound under the steric and electronic influence of ATPH, which enables the vinylogous aldol reaction of α,β-unsaturated carbonyl compounds to give the corresponding γ-aldol products with different regio- and stereoselectivities.
- Saito, Susumu,Nagahara, Takashi,Shiozawa, Masahito,Nakadai, Masakazu,Yamamoto, Hisashi
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p. 6200 - 6210
(2007/10/03)
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- Mixed crossed aldol condensation between conjugated esters and aldehydes using aluminum tris(2,6-diphenylphenoxide)
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The combined use of aluminum tris(2,6-diphenylphenoxide) (ATPH) and lithium 2,2,6,6-tetramethylpiperidide (LTMP) has proven to be effective for the mixed crossed aldol condensation between conjugated esters and various aldehydes. An example is shown in Eq
- Saito, Susumu,Shiozawa, Masahito,Yamamoto, Hisashi
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p. 1769 - 1771
(2007/10/03)
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- Cadmium chloride mediated regiocontrol of dienolates and ketene thioacetals: γ condensation with aldehydes
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The use of cadmium chloride to control the regioselectivity of vinylogous anions upon condensation with aldehydes is described.Addition occurred preferentially at the γ position with substituted crotonates and 2-ethylidene-1,3-dithiane (6).Experiments dem
- Lei, Bo,Fallis, Alex G.
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p. 1450 - 1456
(2007/10/02)
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- Dienediolates from Unsaturated Carboxylic Acids. Reaction with para-Substituted Benzaldehydes. Electronic Effects on Regioselectivity
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Regioselectivity α/γ ratios for addition of the lithium dienediolate of crotonic acid to para-substituted benzaldehydes are subject to small electronic effects when reactions are carried out at low temperature, but strong influence by substituents is observed on heating for 1 h at 60 deg C.A linear correlation is then found between regiochemical ratios and ?p parameters.Stereoselectivity RR/RS ratios (33:66 to 43:57) for α-adducts obtained in the cold do not depend on the substituents.
- Parra, Margarita,Mestres, Ramon,Aparicio, Domitila,Durana, Nieves,Rubiales, Gloria
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p. 327 - 332
(2007/10/02)
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- REFORMATSKY REACTION USING Zn/Ag COUPLE
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The Reformatsky reaction is easy to run in ethereal solvents in the presence of Zn/Ag couple.From methyl γ-bromocrotonate and krtones, remified esters are fromed in refluxing Et2O, linear ones in refluxing THF.
- Bortolussi, Michel,Seyden-Penne, Jacqueline
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p. 2355 - 2362
(2007/10/02)
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- Condensation of Crotonic and Tiglic Acid Dianions with Aldehydes and Ketones
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The lithium dianions of crotonic and tiglic acids reacted with n-heptanal, benzaldehyde, isobutyraldehyde, 2,2-dimethyl-3,3-dimethoxypropionaldehyde, acetone, and cyclopentanone at -78 deg C, room temperature, and 65 deg C to give α- and γ-condensation products.The kinetically controlled pathway gives largely or entirely the β-hydroxy acid from condensation at the α-carbon, but at higher temperature the reaction is reversible leading to the more stable δ-hydroxy α,β-unsaturated acid.In addition to the reaction temperature, steric effects associated with both the carbonyl electrophile and the acid dianion were found to influence the α:γ ratio of condensation products.
- Johnson, Paul R.,White, James D.
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p. 4424 - 4429
(2007/10/02)
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- A General Synthesis of 5,6-Dihydro-α-pyrones
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Crotonate esters substituted at C-3 by alkyl, alkoxy, or dialkylamino groups are deprotonated and the resulting dienolates added to aldehydes and ketones.Kinetic reaction is at C-2 of the ester, leading to the isolation of 2-alkyl-3-hydroxy esters such as 3 and 4 if the reaction mixture is quenched at -70 deg C.However, retroaldolization occurs readily.If the initial reaction mixtures are allowed to warm to 15 deg C before workup, the isolated products are 5,6-dihydro-α-pyrones (such as 5), accompanied in some cases by the (E)-4-substituted crotonate (such as 6).The method has been applied to the synthesis of a series of retinoid lactones (5f,18,21a-c) which are of interest as potential antineoplastic agents.
- Dugger, R.W.,Heathcock, Clayton H.
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p. 1181 - 1185
(2007/10/02)
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