Asymmetric induction. 3. Enantioselective deprotonation by chiral lithium amide bases

Whitesell, James K.; Felman, Steven W.

doi:10.1021/jo01292a055

Cited by 151 publications

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“…Epoxidation of alkenes followed by epoxide opening with metal amide is also well-known. [2][3][4][5][6] During the course of the synthetic investigation of diversifolin, we found that treatment of g,d-unsaturated carboxylic acid 1 with 2.0 eq of phenylselenenyl chloride (PhSeCl) in pyridine at 50°C, followed by oxidation with hydrogen peroxide, provided g-butyrolactone 2 in 44% yield (Chart 1). …”

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confidence: 99%

A PhSeCl-Mediated Allylic Oxidation of Prenyl Moiety: A Convenient Method for the Construction of 3-Isopenten-2-ol Unit

Oshida

Nakamura

Nakazaki

et al. 2008

CHEMICAL & PHARMACEUTICAL BULLETIN

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A number of methodologies for the oxidation of alkenes to allylic alcohols have been developed (Fig. 1).1) For example, selenium dioxide and chromate reagents generally oxidize the allylic position without rearrangement of the carbon-carbon double bond. In contrast, singlet oxygen affords the allylic alcohol with the rearrangement of the carbon-carbon double bond. Epoxidation of alkenes followed by epoxide opening with metal amide is also well-known. [2][3][4][5][6] During the course of the synthetic investigation of diversifolin, we found that treatment of g,d-unsaturated carboxylic acid 1 with 2.0 eq of phenylselenenyl chloride (PhSeCl) in pyridine at 50°C, followed by oxidation with hydrogen peroxide, provided g-butyrolactone 2 in 44% yield (Chart 1). 7)This result means that allylic oxidation of the trisubstituted alkene proceeded in addition to the planned selenolactonization of the 4-alkenoic acid moiety. Herein we wish to report the scope and limitations of the phenylselenenyl chloridemediated allylic oxidation of alkenes.At first, we investigated the optimization of this oxidation using citronellyl acetate 3 as a model substrate. As shown in Table 1, the reaction of 3 proceeded in a similar manner (PhSeCl-pyridine, 50°C) as 1 to give the corresponding allyl alcohol 4 in 66% yield (entry 1).8) When other readily available phenylselenium reagents were applied in the reaction, neither phenylselenenyl bromide (PhSeBr) nor N-PSP (Nphenylselenenylphthalimide) were effective for this transformation (entries 2, 3). Although the reactions in benzene, triethylamine, and 2,6-lutidine yielded poor results, the reaction in acetonitrile gave 4 in 31% yield (entries 4-7). As shown in entries 8 and 9, higher reaction temperatures resulted in a slight decrease in the yield probably due to decomposition of 4. These results indicate that treatment with PhSeCl in pyridine at 50°C gave the best result.With optimum conditions established, we next carried out the oxidation of a variety of other substrates 5a-j as shown in Table 2.8) The reaction of 2-methyl-2-undecene (5a) gave the corresponding allyl alcohol 6a in 55% yield (entry 1), while 1,1-diethyl substituted derivative 5b gave 6b in a very low yield due to steric hindrance around the trisubstituted olefin (entry 2). In contrast, cyclohexylidene derivative 5c produced 6c in higher yield than in the case of 5b (entry 3). This result might be attributed to inflexibility of the cyclohexane ring in 5c. Although the allylic oxidations of nerol 5d and citronerol 5f afforded the corresponding diols 6d and 6f A phenylselenenyl chloride (PhSeCl)-mediated allylic oxidation to give allylically rearranged alcohol has been developed. A possible mechanism for the present reaction is generation of allylic selenide from prenyl moiety via [1,3]-sigmatropic rearrangement, followed by oxidation and [2,3]-sigmatropic rearrangement to afford 3-isopenten-2-ol.

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confidence: 99%

A PhSeCl-Mediated Allylic Oxidation of Prenyl Moiety: A Convenient Method for the Construction of 3-Isopenten-2-ol Unit

Oshida

Nakamura

Nakazaki

et al. 2008

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…Enantioselective isomerization of achiral epoxides to optically active allylic alcohols with chiral lithium amides (from BuLi and enantiomerically pure secondary amines) has recently been described by Whitesell and Felman [17] and Asami [18]. The yield and enantiomeric excess strongly depend on the epoxide, the base, and the solvent.…”

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confidence: 99%

Asymmetric Catalysis by Vitamin B₁₂. The isomerization of achiral epoxides to optically active allylic alcohols

Walder

Zhang

et al. 1988

Helvetica Chimica Acta

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Achiral epoxides are isomerized to optically active allylic alcohols under the influence of catalytical amounts of cob(1)alamin in protic polar solvents.Introduction. -The isomerization of epoxides to allylic alcohols is an important transformation in organic synthesis and an industrial process [l] Enantioselective isomerization of achiral epoxides to optically active allylic alcohols with chiral lithium amides (from BuLi and enantiomerically pure secondary amines) has recently been described by Whitesell and Felman [17] and Asami [18]. The yield and enantiomeric excess strongly depend on the epoxide, the base, and the solvent.Continuing our investigations on the application of vitamin B,, [19] as catalyst in organic synthesis [20], we report here on preliminary results on the B,,-catalyzed isomerization of achiral epoxides to optically active allylic alcohols. This work was stimulated to a considerable extent by earlier findings of Fischli et al. on the cob(1)alamin-catalyzed enantioselective hydrogenation of Michael-olefins [2 11 and the work of Golding and coworkers on the stereochemistry of the alkylation of cob(1)alamin by racemic epoxides [221.Results and Discussion. ~ If achiral epoxides like la, b, d are dissolved in a polar protic solvent containing a catalytic amount of vitamin B,,, [23], the corresponding optically active allylic alcohols 2a, b, dare formed on standing at room temperature (Scheme). The

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“…The enantioselective base-promoted rearrangement of oxiranes was achieved by Whitesell and Felman in 1980 38 . Various homochiral lithium amides were used for the isomerization of cyclohexene oxide with an enantiomeric excess (ee) up to 36% with the employment of 50 in refluxing THF (Scheme 24).…”

Section: B Enantioselective Access To Allylic Alcohols Via Asymmetrimentioning

confidence: 99%

Reactivity of Oxiranes with Organolithium Reagents

Chemla

Vrancken

2009

Patai's Chemistry of Functional Groups

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Asymmetric induction. 3. Enantioselective deprotonation by chiral lithium amide bases

Cited by 151 publications

References 2 publications

A PhSeCl-Mediated Allylic Oxidation of Prenyl Moiety: A Convenient Method for the Construction of 3-Isopenten-2-ol Unit

A PhSeCl-Mediated Allylic Oxidation of Prenyl Moiety: A Convenient Method for the Construction of 3-Isopenten-2-ol Unit

Asymmetric Catalysis by Vitamin B₁₂. The isomerization of achiral epoxides to optically active allylic alcohols

Reactivity of Oxiranes with Organolithium Reagents

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Asymmetric induction. 3. Enantioselective deprotonation by chiral lithium amide bases

Cited by 151 publications

References 2 publications

A PhSeCl-Mediated Allylic Oxidation of Prenyl Moiety: A Convenient Method for the Construction of 3-Isopenten-2-ol Unit

A PhSeCl-Mediated Allylic Oxidation of Prenyl Moiety: A Convenient Method for the Construction of 3-Isopenten-2-ol Unit

Asymmetric Catalysis by Vitamin B12. The isomerization of achiral epoxides to optically active allylic alcohols

Reactivity of Oxiranes with Organolithium Reagents

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Asymmetric Catalysis by Vitamin B₁₂. The isomerization of achiral epoxides to optically active allylic alcohols