20859-10-3Relevant articles and documents
In situ generation of 2,3-allenolates in the coupling of secondary homopropargylic alcohols and aldehydes
Miranda, Pedro O.,Ramírez, Miguel A.,Padrón, Juan I.,Martín, Víctor S.
, p. 283 - 286 (2006)
A study on a novel oxonia [3,3]-sigmatropic rearrangement as competitive alternative pathway to the acetylenic Prins cyclization on the addition of secondary homopropargylic alcohols to aldehydes catalyzed by iron(III) is described. 'Ab initio' theoretica
An access to α, β-unsaturated ketones via dual cooperative catalysis
Syamala, Lakshmi V.R. Babu,Khopade, Tushar M.,Warghude, Prakash K.,Bhat, Ramakrishna G.
supporting information, p. 88 - 91 (2018/12/05)
A dual cooperative organocatalytic approach for the synthesis of α, β-unsaturated ketones is described. This one pot transformation is realized via a domino Knoevenagel-Michael-retro Michael reaction sequence. Various aliphatic ketones reacted smoothly with aromatic as well as aliphatic aldehydes in presence catalytic amount of Meldrum's acid and bifunctional amine. The highlights of this protocol are the easy availability of catalysts, high selectivity, and functional group tolerance. The reaction proved to highly E-selective with no side products emanating from self-condensation, unlike the base-mediated reactions.
The cinchona primary amine-catalyzed asymmetric epoxidation and hydroperoxidation of α,β-unsaturated carbonyl compounds with hydrogen peroxide
Lifchits, Olga,Mahlau, Manuel,Reisinger, Corinna M.,Lee, Anna,Fares, Christophe,Polyak, Iakov,Gopakumar, Gopinadhanpillai,Thiel, Walter,List, Benjamin
supporting information, p. 6677 - 6693 (2013/06/05)
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.
Synthesis of E-α,β-unsaturated ketones with complete stereoselectivity via sequential aldol-type/elimination reactions promoted by samarium diiodide or chromium dichloride
Concellón, José M.,Rodríguez-Solla, Humberto,Concellón, Carmen,Díaz, Pamela
, p. 837 - 840 (2007/10/03)
E-α,β-Unsaturated ketones can be obtained with complete E-selectivity by a sequential reaction of dichloroketones with a variety of aldehydes. This transformation was promoted by SmI2, SmI2 in the presence of FeCl3 or CrCl2. The best results were obtained when CrCl2 was used as the metallating agent. A mechanism based on a successive aldol-type reaction and a β-elimination is proposed to explain these results. Georg Thieme Verlag Stuttgart.
Stereocontrolled total synthesis of (+)-leucascandrolide A
Paterson, Ian,Tudge, Matthew
, p. 343 - 347 (2007/10/03)
Apparently no longer available from its natural source is the potent cytotoxic and antifungal agent leucascandrolide A (1), which was initially isolated from a New Caledonian calcareous sponge. A highly stereocontrolled total synthesis of this structurally unique macrolide commences with a Jacobsen asymmetric hetero Diels-Alder reaction to configure the tetrahydropyran ring. An efficient endgame relies on two Mitsunobu reactions, the first to generate the 18-membered macrolactone and the second to attach the oxazole-bearing side chain.
A new protocol for a regioselective aldol condensation as an alternative convenient synthesis of β-ketols and α,β-unsaturated ketones
Kourouli, Therapia,Kefalas, Panagiotis,Ragoussis, Nikitas,Ragoussis, Valentine
, p. 4615 - 4618 (2007/10/03)
A general and convenient synthesis of β-ketols and α,β-alkenones has been achieved by a Knoevenagel condensation of a β-ketoacid with an aldehyde in aqueous medium. Saponification of a β-ketoester by an aqueous KOH 10% solution gives the potassium salt of the β-ketoacid, which is condensed in situ with an aldehyde at pH 7.8-8.0, at 60 °C for 5-6 h. The intermediate β-ketocarboxylate is smoothly decarboxylated in the reaction medium, giving the β-ketol in high yield (75-90%). Acidification of the reaction mixture at pH 1 and heating at 70 °C under vigorous stirring for 6 h, leads directly to the corresponding α,β-unsaturated ketone in good yield (65-75%).
Proline-catalyzed asymmetric aldol reactions between ketones and alpha-unsubstituted aldehydes.
List,Pojarliev,Castello
, p. 573 - 575 (2007/10/03)
[reaction: see text] With this communication we extend the methodology of proline-catalyzed direct asymmetric aldol reactions to include alpha-unsubstituted aldehydes as acceptors. This important aldehyde class gives the corresponding aldols in 22-77% yield and up to 95% ee when the reactions are performed in pure acetone or in ketone/chloroform mixtures. On the basis of these results we have developed a concise new synthesis of (S)-ipsenol.
Copper-catalysed asymmetric 1,4-addition of organozinc compounds to linear aliphatic enones using 2,2′-dihydroxy 3,3′-dithioether derivatives of 1,1′-binaphthalene
Boerner, Christoph,Dennis, Michael R.,Sinn, Ekkehard,Woodward, Simon
, p. 2435 - 2446 (2007/10/03)
Directed ortho dilithiation of bis(diethylcarbamate) or bis(MOM)-protected (Sa)-1,1,′-bi(2-naphthol) followed by treatment with R2S2 [R = Me, Ph (X-ray structure)] or Me2Se2 cleanly affords the 3,3′ derivatives; the free naphthols are produced on deprotection. In the case of the bis(MOM) series, but not that of the bis(carbamates), some racemisation occurs. The ligand 2,2′-dihydroxy-3,3′-dimethylthio-1,1′-binaphthalene shows optimal performance in the addition of ZnEt2 to linear aliphatic enones (E)-R1C(O)CH=CHR2. Variation of the steric demands of R1 and R2 generates catalytic results consistent with binding of a zinc-based Lewis acid anti to the ene function and with the reactive conformation being s-cis. With enones containing the functions R2 = (CH2)nCH(OAlkyl)2 (n = 0-2), the ZnEt2 addition products undergo base-promoted cyclisation.
Wittig reactions in the ionic solvent [bmim][BF4]
Boulaire, Virginie Le,Gree, Rene
, p. 2195 - 2196 (2007/10/03)
The ionic salt [bmim][BF4] is an attractive solvent for Wittig reactions, allowing both easier separation of alkenes from Ph3PO together with eficient reuse to the solvent.
Dynamic kinetic resolution of allylic alcohols mediated by ruthenium- and lipase-based catalysts.
Lee,Huh,Kim,Jung,Koh,Park
, p. 2377 - 2379 (2007/10/03)
An enzyme-metal combo reaction has been developed for the dynamic kinetic resolution of allylic alcohols in which racemic substrates are transformed by a lipase and a ruthenium complex in the presence of an acyl donor to allylic acetates of high optical purity in over 80% yield.
