Allylbarium Reagents: Unprecedented Regio- and Stereoselective Allylation Reactions of Carbonyl Compounds

Yanagisawa, Akira; Habaue, Shigeki; Yasue, Katsutaka; Yamamoto, Hisashi

doi:10.1021/ja00093a010

Cited by 164 publications

(81 citation statements)

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“…However, a complete a-regioselectivity can hardly be achieved since it varies depending on the nature not only of the allylic metal reagents, but also of aldehydes, promoters, and reaction conditions. [5] Appreciably high a-selective allylation is observed in the reaction of aldehydes with allylic barium, [6] and allylic cerium reagents. [7] However, these metal-mediated allylations are very difficult to handle because the reactions have to be performed under strictly anhydrous, oxygen-free, and low temperature conditions.…”

Section: Introductionmentioning

confidence: 99%

Allylation of Aldehydes Promoted by the Cerium(III) Chloride Heptahydrate/Sodium Iodide System: the Dependence of Regio‐ and Stereocontrol on the Reaction Conditions

Bartoli¹,

Giuliani²,

Marcantoni³

et al. 2005

Adv Synth Catal

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Abstract:The cerium(III) chloride heptahydrate/sodium iodide complex (CeCl 3 · 7 H 2 O/NaI) acts as a useful promoter in the carbon-carbon bond forming reaction by addition of allyltributylstannanes to aldehydes. The reaction of 2-butenyltributylstannane shows that the regio-and the stereochemical outcomes depend on the reaction conditions. When the promoter is adsorbed on a solid support (aluminum oxide), a highly prevalent formation of the g-adduct is observed in solvent-free conditions. Conversely, when the reaction is carried out in acetonitrile as the solvent, the a-adduct largely prevails. In the last case, a complete stereocontrol is observed, the less stable (Z)-isomer being obtained in high geometrical purity.

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Section: Introductionmentioning

confidence: 99%

Allylation of Aldehydes Promoted by the Cerium(III) Chloride Heptahydrate/Sodium Iodide System: the Dependence of Regio‐ and Stereocontrol on the Reaction Conditions

Bartoli¹,

Giuliani²,

Marcantoni³

et al. 2005

Adv Synth Catal

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“…[8] For most other cases, including metals such as lithium, magnesium, zinc, chromium, samarium, and indium, only tentative mechanistic discussions are possible at present. [3,5] Even if the position of the equilibrium in set A is known, [9,10] on account of the Curtin Hammett principle this may not be relevant to the stereoselectivity attained on reaction with an aldehyde when the equilibration within set A is more rapid than the addition to the aldehyde. Rate constants for haptotropic rearragentments of allylmetal compounds have been determined in some cases, [10,11,12] but in the absence of knowledge about the rate of reaction with an aldehyde these data do not delineate which mechanistic situation [13] ÐCurtin Hammett (dynamic kinetic resolution) or non-Curtin Hammett (thermodynamic or dynamic thermody-namic resolution)Ðprevails in a given system.…”

Section: Introductionmentioning

confidence: 99%

On the Constitutional Stability ofη1-Allylmetal Compounds

Hoffmann

Polachowski

1998

Chem. Eur. J.

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Many h 1 -allymetal species undergo a rapid haptotropic rearrangement. The stereochemical outcome of reactions of these allylmetal species with aldehydes depends on whether the haptotropic rearrangement is faster or slower than the reaction with the aldehyde. We present here a test system based on kinetic resolution, by which just this information becomes available. Thus, haptotropic rearrangement of cyclohexenyllithium, -magnesium chloride, -titanium triisopropoxide, and -titanium tetraisopropoxide, was found to be faster than addition to the aldehyde 9. Borotropic rearrangement in cyclohexenyldiethylborane was found to be slower than the addition to the aldehyde 9.

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“…Allyl barium reagents had been reported to add exclusively in a 1,4 fashion to unsaturated ketones with almost complete suppression of the g adduct and double-bond isomerisation. [36] However, attempted addition of allylic barium reagent 24 b, even in large excess, to enone 21 proved fruitless. Finally, 1,4-addition of a simple allyl system to enone 21 was investigated.…”

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confidence: 99%

The Truth about False Unicorn (Chamaelirium luteum): Total Synthesis of 23R,24S‐Chiograsterol B Defines the Structure and Stereochemistry of the Major Saponins from this Medicinal Herb

Matovic

Stuthe

Challinor

et al. 2011

Chemistry A European J

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Chamaelirium luteum is used in traditional medicine systems and commercial botanical dietary supplements for the treatment of female reproductive health problems. Despite the wide use of this herb, only very limited phytochemical characterisation is available. Our investigation of C. luteum roots led to the isolation of two new steroidal saponins 1 and 2 that contain an unusual aglycone 3. The absolute configurations of these molecules were unable to be determined spectroscopically and thus the total synthesis of 3 was undertaken and achieved in 16 steps and 1.6 % overall yield from pregnenolone. The key step in the synthesis was the stereoselective installation of the side chain at C-17 and C-20, which employed anion-accelerated oxy-Cope methodology. The relative configuration of aglycone 3 was determined by X-ray crystallography of an advanced synthetic intermediate. The absolute configuration was based upon that of the pregnenolone-derived steroidal skeleton and determined to be 23R,24S.

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Allylbarium Reagents: Unprecedented Regio- and Stereoselective Allylation Reactions of Carbonyl Compounds

Cited by 164 publications

References 0 publications

Allylation of Aldehydes Promoted by the Cerium(III) Chloride Heptahydrate/Sodium Iodide System: the Dependence of Regio‐ and Stereocontrol on the Reaction Conditions

Allylation of Aldehydes Promoted by the Cerium(III) Chloride Heptahydrate/Sodium Iodide System: the Dependence of Regio‐ and Stereocontrol on the Reaction Conditions

On the Constitutional Stability ofη1-Allylmetal Compounds

The Truth about False Unicorn (Chamaelirium luteum): Total Synthesis of 23R,24S‐Chiograsterol B Defines the Structure and Stereochemistry of the Major Saponins from this Medicinal Herb

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