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Enolates Aldol reaction

A powerful variation of the iron acetyl enolate aldol reaction utilizes the cnolate of complex 8 which bears a (pentafluorophenyl)diphenylphosphane ligand in place of the more usual triphenylphosphane47. The enolate species 9. prepared by treatment of 8 with lithium diiso-propylamide, reacts at — 78 °C with benzaldehyde to produce the aldol adduct 10 with a d.r. of 98.5 1.5. [Pg.537]

The value of 2-acyl-1,3-dithiane 1-oxides in stereocontrolled syntheses has been extended to the enantioselective formation of (3-hydroxy-y-ketoesters through ester enolate aldol reactions <00JOC6027>. [Pg.335]

As shown in Scheme 9.31, the (S)-enolate (100a), from Evans reagent 100. reacts on its Re face if the metal is not coordinated to the oxazolidone carbonyl group at the time of electrophilic attack, which is the normal situation in an uncatalysed boron enolate aldol reaction (see Scheme 9.14) and on the Si face if the metal is coordinated to the oxazolidone carbonyl group (lOOb), which is the normal situation in enolate alkylation (see 9.3.2). [Pg.269]

A diastereoselective titanium-enolate aldol reaction of (.S )-1 -bcnzyloxy-2-mclhyl - (g) pentan-3-one has been reported.151... [Pg.17]

Crotonyl Enolate Aldol Reactions. Boron enolates of the A/-crotonyloxazolidinones have been shown to afford the expected. n-aldol adducts (eq 36). The propensity for selfcondensation during the enolization process is minimized by the use of triethylamine over less kinetically basic amines. [Pg.62]

Representative examples of the reactions of various carbonyl compounds with Grignard reagents under these conditions are listed in Table 5. It is emphasized that enolization, aldol reaction, ester condensation, reduction and 1,4-addition are remarkably suppressed by the use of cerium chloride. Various tertiary alcohols, which are difficult to prepare by the conventional Grignard reaction, can be synthesized by this method. [Pg.248]

Bernard , A., Capelli, A. M., Comotti, A., Gennari, C., Gardner, M., Goodman, J. M., Paterson, I. Origins of stereoselectivity in chiral boron enolate aldol reactions a computational study using transition state modeling. Tetrahedron 1991, 47, 3471-3484. [Pg.533]

The reactions of enolates with aldehydes (aldol reactions) or with imines have been widely developed since the 1970s. Asymmetric aldol-type reactions are very important in the multistep synthesis of complex molecules such as ionophores or p-lactam antibiotics. Chirality has been introduced either on the substituents of boron, on the metal ligands or on the carbon skeleton of the enolate. Aldol reactions are usually run at low temperatures, and when metal enolates are used, the reactions are sometimes easily reversible [160, 209],... [Pg.306]

Of course, under many conditions, the preformed enolate aldol reaction appears to be significantly exothermic. The additional driving force is presumably provided by the enthalpy of coordination of the ambident aldolate ion with a cation. The importance of cation solvation in providing a driving force for the aldol reaction has been elegantly demonstrated by Noyori and coworkers.In this important experiment, the tris(dimethylamino)sulfonium (TAS" ) enolate of l-phenyl-2-propanone was prepared as shown in equation (6). The naked enolate was obtained as a yellow crystalline material, free of trimethylsilyl fluoride, by concentration of the THF solution. [Pg.135]

Offenhauer and Nelsen discovered that boric acid is an excellent catalyst for aldol condensations treatment of heptanal with boric acid in refluxing toluene under a Dean-Stark trap gives the condensation product in quantitative yield (equation 10). The authors suggested an intermediate enol borate this was probably the flrst example of a boron enolate aldol reaction. [Pg.138]

The foregoing results clearly constitute an encouraging lead, and represent the best that has yet been done with chiral auxiliaries for lithium enolate aldol reactions. Although the chiral auxiliary is not covalently attached to either reactant, it is still used stoichiometrically. Furthermore, the process has only been demonstrated with the aldol reaction in equation (133). It will be interesting to see if the efficacy of this method will extend to other enolates and aldehydes. [Pg.234]

The high syn stereoselectivity attained in zirconium enolate aldol reactions has proved useful in complex natural product synthesis. The zirconium-mediated aldol reaction of the chiral ethyl ketone (9) with a chiral aldehyde has been used by Masamune et al. to give selectively adduct (10), which was further elaborated into the ansa chain of rifamycin S (equation 1). Good enolate diastereofacial selectivity is also obtained here and leads to a predominance of one of the two possible syn adducts. A zirconium enolate aldol reaction also features in the Deslongchamps formal total synthesis of erythromycin A, where the di(cyclopentadienyl)chiorozirconium enolate from methyl propionate adds with high levels of Cram selectivity to the chiral aldehyde (11) to give the syn adduct (12 equation 2). A further example is... [Pg.303]

In some cases titanium enolates give as good, if not better, stereoselectivity as the corresponding boron enolate aldol reactions (Volume 2, Chapter 1.7). For example, the tri(isopropoxy)titanium enolate of the chiral ethyl ketone (27) has been found to undergo aldol reactions with aldehydes with very high dia-... [Pg.307]


See other pages where Enolates Aldol reaction is mentioned: [Pg.68]    [Pg.68]    [Pg.62]    [Pg.136]   
See also in sourсe #XX -- [ Pg.73 , Pg.74 , Pg.75 , Pg.76 , Pg.77 , Pg.78 ]

See also in sourсe #XX -- [ Pg.169 ]

See also in sourсe #XX -- [ Pg.2 ]

See also in sourсe #XX -- [ Pg.152 , Pg.182 ]

See also in sourсe #XX -- [ Pg.152 , Pg.181 , Pg.182 , Pg.235 ]

See also in sourсe #XX -- [ Pg.169 ]

See also in sourсe #XX -- [ Pg.692 ]

See also in sourсe #XX -- [ Pg.2 ]

See also in sourсe #XX -- [ Pg.152 , Pg.182 ]




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Acetate enolates enantioselective aldol reaction

Aldehyde lithium enolates aldol reaction

Aldehydes aldol reactions with silyl enol ethers

Aldehydes aldol reactions, silyl enol ethers, scandium

Aldimines lithium enolate aldol reaction

Aldol Reaction Using Silyl Enol Ethers

Aldol Reaction of Boron Enolates

Aldol Reaction with () and (Z) Enolates

Aldol Reactions Using Polymer-Supported Silyl Enol Ethers

Aldol Reactions of Chiral Imides and Ester Enolates

Aldol Reactions via Activation of Silyl Enolates

Aldol condensation aldehyde reaction with enolates

Aldol condensation ketone reaction with enolates

Aldol reaction boron enolates

Aldol reaction chiral enolates

Aldol reaction enol ethers

Aldol reaction enolate anions

Aldol reaction enolate equivalents

Aldol reaction ester enolates

Aldol reaction ketone enolates

Aldol reaction of ketone enolates

Aldol reaction silyl enol ether

Aldol reaction using chiral enolates

Aldol reaction using tin enolates

Aldol reactions With boron enolates

Aldol reactions With silyl enol ethers

Aldol reactions With titanium enolates

Aldol reactions acetyliron enolates

Aldol reactions aldehydes/silyl enol ethers

Aldol reactions lithium enolates

Aldol reactions magnesium enolates

Aldol reactions of lithium enolates

Aldol reactions of silyl enol ethers

Aldol reactions of trichlorosilyl enol ethers

Aldol reactions silyl enol ethers/acetals

Aldol reactions titanium enolates

Aldol-Type Reaction with Silyl Enolates

Aldol-type reactions silyl enol ether

Allenyl enolate aldol reactions

Allenyl enolates aldol reaction

Aluminum enolates aldol reactions

Ammonium enolates enantioselective aldol reaction

Asymmetric Aldol Reaction of Silyl Enolates

Asymmetric Aldol Reactions via Zirconium Enolates

Asymmetric aldol reactions using boron enolates

Asymmetric aldol reactions using chiral boron enolates

Asymmetric aldol reactions using ketone-derived enolates

Azetidinone, diaryllithium enolates aldol reactions

Boron and Silicon Enolates in Crossed Aldol Reaction

Boron enolates aldol condensation reactions

Boron enolates, aldol reactions mediated

Boryl enolates aldol reactions

Calcimycin aldol reaction of magnesium enolate

Cerium enolates aldol reaction

Chiral auxiliaries lithium enolate aldol reaction

Chiral lithium enolates aldol reaction diastereoselectivity

Cobalt enolates aldol reaction

Copper® enolates enantioselective aldol reaction

Crossed Aldol Reactions Using Silicon Enolates

Crotonic acid, 3-methylethyl ester enolates, aldol reaction

Cyclohexanone, aldol reaction enol content

Cyclohexanone, aldol reaction enolate ion

Diastereoselective Aldol Reactions via Zirconium Enolates

Diastereoselective synthesis aldol reactions, chiral enolates

Directed aldol reaction preformed lithium enolates

Discovery of Aldol Reaction Mediated by Boron Enolates

Discovery of Silicon Enolate-mediated Crossed Aldol Reactions

Enantioselective aldol reaction lithium enolates

Enol ethers Mukaiyama aldol reaction

Enol ethers, trimethylsilyl aldol reaction

Enol ethers, trimethylsilyl syn selective aldol reaction

Enol silane, Mukaiyama aldol reaction

Enol silanes aldol reaction

Enolate compounds aldol reactions

Enolate compounds asymmetric aldol reactions

Enolate in aldol reactions

Enolates aldol addition reactions

Enolates aldol condensation reactions

Enolates aldol reaction with

Enolates aldol reaction, stereoselectivity

Enolates aldol reactions, asymmetric

Enolates in aldol reactions

Enols aldol reactions

Enols aldol reactions

Erythronolide aldol reaction of lithium enolate

Evans aldol reaction, boron enolates

Evans asymmetric aldol reactions enolates

In Situ Direct Generation of Enolates and Their Asymmetric Aldol Addition Reactions

Iron enolates aldol reaction

Ketenes rhodium enolates, aldol reaction

Ketone lithium enolates aldol reaction

Ketones syn selective aldol reaction, titanium enolates

Ketones syn selective aldol reaction, zirconium enolates

Lanthanide metal enolates aldol reaction

Lewis Acid-catalyzed Aldol Reactions of Silicon Enolates

Lewis Base-catalyzed Aldol Reactions of Trimethylsilyl Enolates

Lewis acids titanium enolate aldol reactions

Lithium enolates complex’ aldol reactions

Lithium enolates directed aldol reaction

Lithium enolates in aldol reactions

Mercury enolates aldol reaction

Metal enolates mixed aldol reaction

Metal enolates, diastereoselective aldol reaction

Molybdenum enolates aldol reaction

Mukaiyama aldol reaction trimethylsilyl enol ether

Natural Product Synthesis via Titanium Enolate Aldol Reactions

Propionate enolate enantioselective aldol reaction

Reactions of enolates with aldehydes and ketones the aldol reaction

Rhenium enolates aldol reactions

Rhodium enolates aldol reaction

Silyl enol ethers Lewis acid catalysed aldol reaction

Silyl enol ethers Mukaiyama aldol reactions

Silyl enol ethers aldol addition reactions

Silyl enol ethers aldol condensation reactions

Silyl enol ethers in aldol reactions

Silyl enolates, aldol reactions, scandium

Stannous enolates, stereoselective aldol reaction

Tandem reactions lithium enolate aldol reaction

Tin enolates aldol reactions

Titanium, tris enolates aldol reaction, syn stereoselectivity

Titanium, tris enolates aldol reaction, syn.anti selectivity

Transition metal enolates aldol reaction

Tungsten enolates aldol reaction

Zinc enolates aldol reaction

Zirconium enolates aldol reactions

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