Bis(oxazoline)–ligand-mediated asymmetric [2,3]-Wittig rearrangement of benzyl ethers: reaction mechanism based on the hydrogen/deuterium exchange effect

Kitamura, Maria; Hirokawa, Yoshimi; Yoshioka, Yuki; Maezaki, Naoyoshi

doi:10.1016/j.tet.2012.03.059

Cited by 12 publications

(5 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Stereoselective [2,3]-Wittig rearrangement reactions employing stoichiometric chiral ligands have been shown to proceed via rate- and enantioselectivity-determining deprotonation followed by stereospecific rearrangement. − In the catalytic system described here, deprotonation, substrate-binding, or rearrangement could, in principle, be enantiodetermining. To distinguish between these possibilities, isotope effects were measured for substrates deuterated at the α ( 1a - d 1,α ) and allylic ( 1a - d 2, allylic ) positions (Scheme A,B).…”

Section: Resultsmentioning

confidence: 99%

Synergistic Ion-Binding Catalysis Demonstrated via an Enantioselective, Catalytic [2,3]-Wittig Rearrangement

2016

View full text Add to dashboard Cite

Sigmatropic rearrangements number among the most powerful complexity-building transformations in organic synthesis but have remained largely insensitive to enantioselective catalysis due to the diffuse nature of their transition structures. Here, we describe a synergistic ion-binding strategy for asymmetric catalysis of anionic sigmatropic rearrangements. This approach is demonstrated with the enantioselective [2,3]-Wittig rearrangement of α-allyloxy carbonyl compounds to afford highly enantioenriched homoallylic alcohol products. Chiral thiourea catalysts are shown to engage reactive anions and their countercations through a cooperative set of attractive, noncovalent interactions. Catalyst structure–reactivity–selectivity relationship studies and computational analyses provide insight into catalyst–substrate interactions responsible for enantioinduction and allude to the potential generality of this catalytic strategy.

show abstract

Section: Resultsmentioning

confidence: 99%

Synergistic Ion-Binding Catalysis Demonstrated via an Enantioselective, Catalytic [2,3]-Wittig Rearrangement

2016

View full text Add to dashboard Cite

show abstract

“…The use of strong Brønsted bases, such as BuLi or tBuLi, with chiral ligands is the most common strategy for acquiring asymmetric products in a [2,3]-rearrangement. 2,4 In addition, boron enolates have been used to achieve the goal. 5 Approaches based on chiral auxiliaries have also been used.…”

mentioning

confidence: 99%

Asymmetric Organocatalytic Wittig [2,3]-Rearrangement of Oxindoles

et al. 2016

View full text Add to dashboard Cite

show abstract

“…In addition, the α and α′ [1,2] rearrangement products (±)- 18 and (±)- 19 were isolated as minor byproducts (both ∼8% yield) and fully characterized. Attempts aiming at an asymmetric [2,3]-Wittig rearrangement using chiral BOX ligands − together with various organolithium bases remained unsuccessful (see Table S1).…”

Section: Resultsmentioning

confidence: 99%

Synthesis of (±)-4,5-dia-Parthenolide, an Unnatural Parthenolide Stereoisomer

Freund

Arndt

2016

J. Org. Chem.

View full text Add to dashboard Cite

Parthenolide (PTL), the secondary metabolite of feverfew plant (Tanaceum parthenium), has been used in various medical purposes globally. Inflammation represents a physiological response to injury and helps to restore tissue homeostasis. Inflammation and cancer both are associated with genotoxicity, invasion, metastasis, and abnormal tissue repair mechanisms. PTL inhibit major cellular inflammatory and proliferation pathways like NFκB, STAT3, and MAPK along with the activity and expression of several inflammatory mediators including COX. NFκB pathway plays a key role in controlling cell cycle progression and apoptosis together with metastasis and cancer of various types. Elevated NFκB, Wnt/β-catenin pathways are crucial factors of tumorogenesis. PTL inhibits NFκB and Wnt/β-catenin pathways, and thereby promotes apoptosis and suppresses cell proliferation. Experimental data showed that PTL protects normal cells from apoptosis; whereas in cancer cells it induces apoptotic cell death. Hence, parthenolide could be useful in controlling inflammatory diseases alone or together with tumorogenesis due to its evident anticancer potency and anti-inflammatory nature.

show abstract

Bis(oxazoline)–ligand-mediated asymmetric [2,3]-Wittig rearrangement of benzyl ethers: reaction mechanism based on the hydrogen/deuterium exchange effect

Cited by 12 publications

References 35 publications

Synergistic Ion-Binding Catalysis Demonstrated via an Enantioselective, Catalytic [2,3]-Wittig Rearrangement

Synergistic Ion-Binding Catalysis Demonstrated via an Enantioselective, Catalytic [2,3]-Wittig Rearrangement

Asymmetric Organocatalytic Wittig [2,3]-Rearrangement of Oxindoles

Synthesis of (±)-4,5-dia-Parthenolide, an Unnatural Parthenolide Stereoisomer

Contact Info

Product

Resources

About