Development of Transition Metal-Mediated Cyclopropanation Reactions

DelMonte, Albert J.; Dowdy, Eric D.; Watson, Daniel

doi:10.1007/b94550

Cited by 22 publications

(23 citation statements)

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“…[1][2][3][4][5][6][7] They can also be used as inhibitors and versatile synthetic intermediates. [1][2][3][4][5][6][7] Cyclopropane-containing molecules can be produced from carbenoid-promoted cyclopropanation reactions. Therefore, much effort has been invested to develop carbenoid reagents which can make cyclopropanes from olefins with high efficiency and stereoselectivity.…”

Section: Introductionmentioning

confidence: 99%

On the Mechanism and Stereochemistry of Chiral Lithium‐Carbenoid‐Promoted Cyclopropanation Reactions

Yu-bing

Gao

et al. 2007

Chemistry A European J

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An investigation into the mechanism and stereochemistry of chiral lithium-carbenoid-promoted cyclopropanation reactions by using density functional theory (DFT) methods is reported. Previous work suggested that this type of cyclopropanation reaction may proceed by competition between a methylene-transfer mechanism and a carbometalation mechanism. In this paper, it is demonstrated that the intramolecular cyclopropanation reactions promoted by chiral carbenoids 1 and 2 proceed by the methylene-transfer mechanism. The carbometalation mechanism was found to have a much higher reaction barrier and does not appear to compete with the methylene-transfer mechanism. The Lewis base group does not enhance the carbometalation pathway enough to compete with the methylene-transfer pathway. The present computational results are consistent with experimental observations for these cyclopropanation reactions. The factors governing the stereochemistry of the intramolecular cyclopropanation reaction by the methylene-transfer mechanism were examined to help elucidate the origin of the stereoselectivity observed in experiments. Both the directing group and the configuration at the C(1) centre were found to play a key role in the stereochemistry. Carbenoid 1 has a chiral C(1) centre of R configuration. The Lewis base group directs the cyclization of carbenoid 1 to form a single product. In contrast, the Lewis base group cannot direct the cyclization of carbenoid 2 to furnish a stereoselective product due to the S configuration of the chiral C(1) centre in carbenoid 2. This relationship of the stereochemistry to the chiral character of the carbenoid has implications for the design of new efficient carbenoid reagents for stereoselective cyclopropanation.

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Section: Introductionmentioning

confidence: 99%

On the Mechanism and Stereochemistry of Chiral Lithium‐Carbenoid‐Promoted Cyclopropanation Reactions

Yu-bing

Gao

et al. 2007

Chemistry A European J

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“…Table 2 shows that good yields and purities of 3a were obtained by running the cyclopropanation with smaller amounts (2.5 equiv.) of Al(iBu) 3 in an excess (85 equiv.) of CH 2 Br 2 (Run 1) or with larger amounts (3-4 equiv.)…”

Section: Cyclopropanation With Tiba In Dibromomethanementioning

confidence: 99%

“…[5c] Indeed, Al(iBu) 3 ≈ Al(nPr) 3 ϾϾ AlEt 3 Ͼ Al(nOct) 3 (1) The trialkylaluminum reagents had to be added neat, cosolvents such as dichloromethane and hexane slowed the reaction, whereas Lewis bases such as THF or NEt 3 suppressed the reaction completely. We continued our studies with the readily available and inexpensive Al(iBu) 3 , which can be handled neat by obeying the usual precautions.…”

Section: Cyclopropanation With Tiba In Dibromomethanementioning

confidence: 99%

“…We continued our studies with the readily available and inexpensive Al(iBu) 3 , which can be handled neat by obeying the usual precautions. [10] The temperature, however, had to be carefully monitored during the cyclopropanation reaction, especially at the stage [a] nor-Radjanol (1a) [6] (10 g) and Al(iBu) 3 dissolved in CH 2 Br 2 and heated to reaction temperature, which was maintained by slight external cooling.…”

Section: Cyclopropanation With Tiba In Dibromomethanementioning

confidence: 99%

“…[3] Therefore, we turned our attention to dibromomethane, a much less expensive and more easily purified and stored reagent. Efficient cyclopropanation reactions with CH 2 Br 2 , however, are scarce due to its low reactivity in these reactions.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Transition‐Metal‐Catalyzed Cyclopropanation of Nonactivated Alkenes in Dibromomethane with Triisobutylaluminum

Brunner¹,

Elmer²,

Schröder³

2011

Eur J Org Chem

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The cyclopropanation of nonactivated alkenes with inexpensive triisobutylaluminum (TIBA), in dibromomethane as solvent and reagent, is efficiently catalyzed by FeCl3 at ambient temperature. Catalytic amounts of CuI salts, CpTiCl3, and [CpFe(CO)2]2 are similarly effective. 2‐Methylpropane, generated after quench of excess TIBA can be trapped, and excess dibromomethane can be recycled, which makes the method industrially applicable. Solvent‐free DIBAH or TIBA reduction of unsaturated carbonyl compounds, followed by in situ TIBA cyclopropanation of the unsaturated aluminum alcoholates in dibromomethane give cyclopropyl alkanols. Dienols such as geraniol, linalool or nor‐radjanol are selectively cyclopropanated in their distal position, which allows the synthesis of flavor and fragrance compounds such as Δ‐citral, cis‐javanol, and 7‐methyl‐georgywood. Uncontrollable exothermic events are avoided due to relatively low reaction temperatures made possible by the catalysts and by the addition mode of the reagents.1

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Use of Transition Metal–catalyzed Cascade Reactions in Natural Product Synthesis and Drug Discovery

Xu¹,

Wei²

2013

Catalytic Cascade Reactions

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Development of Transition Metal-Mediated Cyclopropanation Reactions

Cited by 22 publications

References 0 publications

On the Mechanism and Stereochemistry of Chiral Lithium‐Carbenoid‐Promoted Cyclopropanation Reactions

On the Mechanism and Stereochemistry of Chiral Lithium‐Carbenoid‐Promoted Cyclopropanation Reactions

Transition‐Metal‐Catalyzed Cyclopropanation of Nonactivated Alkenes in Dibromomethane with Triisobutylaluminum

Use of Transition Metal–catalyzed Cascade Reactions in Natural Product Synthesis and Drug Discovery

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