Carbon-carbon bond formation with new Mitsunobu reagents

Tsunoda, Tetsuto; Nagaku, Miwa; Nagino, Chisato; Kawamura, Yumi; Ozaki, Fumie; Hioki, Hideaki; Itô, Shô

doi:10.1016/0040-4039(95)00300-2

Cited by 72 publications

(25 citation statements)

References 8 publications

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“…In spite of all the improvements in the redox system, the selection of the acidic component is limited by the pK a value of the pronucleophile for satisfactory results. [12] Falck and co-workers have fine-tuned the acidity of the a-hydrogen atom in carbon nucleophiles with various electron-withdrawing groups to satisfy the requirement for this reaction.…”

mentioning

confidence: 99%

Stereoselective Monofluoromethylation of Primary and Secondary Alcohols by Using a Fluorocarbon Nucleophile in a Mitsunobu Reaction

et al. 2007

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OH is exchanged: An efficient Mitsunobu reaction that uses a fluorinated carbon pronucleophile for the facile synthesis of monofluoromethyl derivatives of alcohols is reported (see scheme; DIAD=diisopropyl azodicarboxylate). This reaction can be performed under mild conditions and is highly feasible for primary, secondary, allylic, benzylic, and alicyclic alcohols. Excellent enantiospecificity is observed for chiral alcohols.

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confidence: 99%

Stereoselective Monofluoromethylation of Primary and Secondary Alcohols by Using a Fluorocarbon Nucleophile in a Mitsunobu Reaction

et al. 2007

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“…However, with benzyl alcohol, it is reported that the concomitant double alkylation and/or an ether forming-reaction takes place. 7) Thus, it is important to develop an efficient approach to this type of reaction, since C-monobenzylation of enolates is an important area of synthetic organic chemistry.…”

mentioning

confidence: 99%

A Facile One-Pot Benzylation of Sodium Enolates Using Trifluoromethanesulfonic Anhydride and Diphenyl Sulfoxide

Takuwa

Minowa

Fujisawa

et al. 2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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Alkylation of metal enolates is one of the most fundamental and frequently used reactions in organic synthesis. This reaction is generally accomplished by treating various metal enolates with alkylating reagents such as alkyl halides or alkyl sulfonates. Such reactions of metal enolates derived from ketones, 1) esters, 2) and b-keto esters 3) with alkyl halides afford a mixture of mono-, di-and poly-alkylated products, even when one equivalent each of base and alkylating reagent are used. For example, O-monobenzylated, Cmonobenzylated and C-dibenzylated products (5 : 45 : 50) were obtained by benzylation of ethyl acetate with benzyl bromide in dimethyl sulfoxide. 4)C-Alkylation of active methylene compounds with alcohols has recently been accomplished in a redox reaction system by Mitsunobu-type reactions, 5) and Tsunoda and coworkers 6) have also reported efficient methods for alkylation of active methylene compounds. However, with benzyl alcohol, it is reported that the concomitant double alkylation and/or an ether forming-reaction takes place. 7) Thus, it is important to develop an efficient approach to this type of reaction, since C-monobenzylation of enolates is an important area of synthetic organic chemistry.The ratio of C-or O-alkylation strongly depends on the nature of the alkylating reagent. Alkoxydiphenyl sulfonium species are known as efficient alkylating reagents in reactions with carbon nucleophiles. Similarly, sulfonium salts derived from dialkylsulfoxides and trifluoromethanesulfonic anhydride have been utilized previously in Swern-type oxidation, 8) sulfilimine synthesis, 9) and glycosylation reactions. 10)Here, we describe a facile one-pot C-benzylation using trifluoromethanesulfonic anhydride and diphenyl sulfoxide. 11) Results and DiscussionGeneration of an alkoxy sulfonium intermediate was first attempted using the bromodiphenyl sulfonium salt derived from diphenyl sulfide and bromine (Chart 1); that is, 1.0 eq of bromine was added to diphenyl sulfoxide in dichloromethane at Ϫ78°C. After stirring the mixture for 10 min, 4-methoxybenzyl alcohol and freshly-prepared sodium enolate of dimethyl malonate were continuously added, followed by slow warming to room temperature. However, the desired product was not obtained. We have previously reported that diphenyl sulfide bis(trifluoromethanesulfonate) reacts with styrene to generate the corresponding active sulfonium intermediate, which in turn reacts with amines to afford aziridines or b,g-unsaturated amines.12,13) Therefore, formation of an alkoxy diphenyl sulfonium intermediate was anticipated upon treatment of an alcohol with diphenyl sulfide bis(trifluoromethanesulfonate). Initially, reaction of 4-methoxybenzyl alcohol with sodium dimethyl malonate was studied as a model system; that is, the diphenyl alkoxy sulfonium intermediate was generated by adding 1.2 eq of 4-methoxybenzyl alcohol to a mixture of trifluoromethanesulfonic anhydride and diphenyl sulfoxide in tetrahydrofuran (THF) at Ϫ78°C. After stirring the mixture for 30 min, 3.0 eq of ...

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“…To the best of our knowledge, there has been no report on the Mitsunobu reaction with fluorocarbon nucleophiles. In spite of all the improvements in the redox system, the selection of the acidic component is limited by the p K a value of the pronucleophile for satisfactory results 12. Falck and co‐workers have fine‐tuned the acidity of the α‐hydrogen atom in carbon nucleophiles with various electron‐withdrawing groups to satisfy the requirement for this reaction 13.…”

Section: Mitsunobu Reaction Of Various Alcohols With 1‐fluoro‐bis(phementioning

confidence: 99%

Tuning the Magnetic Properties of Li_xCrTi_0.25Se₂ (0.03≤x≤0.7) by Directed Deintercalation of Lithium

Behrens¹,

Wontcheu²,

Kiebach³

et al. 2008

Chemistry A European J

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X-ray diffraction (XRD), in situ energy-dispersive X-ray diffraction (EDXRD), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and magnetic measurements were applied to investigate the effects of lithium deintercalation on pseudolayered Li(0.70)CrTi(0.25)Se(2). A detailed picture of structural changes during the deintercalation process was obtained by combining the results of EDXRD and EXAFS. Removal of Li from the host-guest complex leads to anisotropic contraction of the unit cell with stronger impact on the c axis, which is the stacking axis of the layers. The EDXRD experiments evidence that the shrinkage of the lattice parameters with decreasing x(Li) in Li(x)CrTi(0.25)Se(2) is nonlinear in the beginning and then becomes linear. Analysis of the EXAFS spectra clearly shows that the Cr/Ti-Se distances are affected in a different manner by Li removal. The Cr-Se bond lengths decrease, whereas the Ti-Se bonds lengthen when the Li content is reduced, which is consistent with XRD data. Magnetic measurements reveal a change from predominantly antiferromagnetic exchange (theta(p) = -300 K) interactions for the pristine material to ferromagnetic exchange interactions (theta = 25 K) for the fully intercalated material. Thus, the magnetic properties can be altered under ambient conditions by directed adjustment of the dominant magnetic exchange. The unusual magnetic behavior can be explained on the basis of the variation of the metal-metal distances and the Cr-Se-Cr angles with x, which were determined by Rietveld refinements. Owing to competing ferromagnetic and antiferromagnetic exchange interactions and disorder, the magnetic ground state of the intercalated materials is characterized by spin-glass or spin-glass-like behavior.

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Carbon-carbon bond formation with new Mitsunobu reagents

Cited by 72 publications

References 8 publications

Stereoselective Monofluoromethylation of Primary and Secondary Alcohols by Using a Fluorocarbon Nucleophile in a Mitsunobu Reaction

Stereoselective Monofluoromethylation of Primary and Secondary Alcohols by Using a Fluorocarbon Nucleophile in a Mitsunobu Reaction

A Facile One-Pot Benzylation of Sodium Enolates Using Trifluoromethanesulfonic Anhydride and Diphenyl Sulfoxide

Tuning the Magnetic Properties of Li_xCrTi_0.25Se₂ (0.03≤x≤0.7) by Directed Deintercalation of Lithium

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Carbon-carbon bond formation with new Mitsunobu reagents

Cited by 72 publications

References 8 publications

Stereoselective Monofluoromethylation of Primary and Secondary Alcohols by Using a Fluorocarbon Nucleophile in a Mitsunobu Reaction

Stereoselective Monofluoromethylation of Primary and Secondary Alcohols by Using a Fluorocarbon Nucleophile in a Mitsunobu Reaction

A Facile One-Pot Benzylation of Sodium Enolates Using Trifluoromethanesulfonic Anhydride and Diphenyl Sulfoxide

Tuning the Magnetic Properties of LixCrTi0.25Se2 (0.03≤x≤0.7) by Directed Deintercalation of Lithium

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Tuning the Magnetic Properties of Li_xCrTi_0.25Se₂ (0.03≤x≤0.7) by Directed Deintercalation of Lithium