Über tertiäre Carboxoniumsalze

Meerwein, Hans; Bodenbenner, Kurt; Borner, Peter; Kunert, Fritz; Wunderlich, Klaus

doi:10.1002/jlac.19606320107

Cited by 155 publications

(28 citation statements)

References 14 publications

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“…The reaction mixture was extracted with CH 2 Cl 2 ×6, and the combined organic layer was dried. The solvent was evaporated and the residue was dissolved in a small amount of CH 2 5 mg, 1.523 mmol). The resulting suspension was stirred for 30 min, then concentrated in vacuo and the residue was diluted with Et 2 O.…”

Section: Methodsmentioning

confidence: 99%

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Functionalized Oxatriquinanes and Their Structural Equilibrium in Protic Solvent

Suzuki

Muratake

2014

CHEMICAL & PHARMACEUTICAL BULLETIN

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We synthesized oxatriquinane hexafluorophosphate bearing an ethoxycarbonylmethyl group 7 or a 2-oxopropyl group 11. Both of these organic oxonium cation compounds were obtained as stable solids. However, 1 H-NMR analysis showed that oxatriquinane 7 was present as the oxonium cation in aprotic solvent CD 3 CN, but was in rapid equilibrium with ring-opened bicyclic compound 8 in protic solvent CD 3 OD. The oxatriquinane 11 also showed similar behavior in protic solvent. Phenyl-substituted oxatriquinanes 12 and 14 were also obtained as stable solids, and showed similar properties to 7 and 11. Key words oxatriquinane; organic oxonium cation; equilibrium; protic solventThere have been few reports on stable organic oxonium salts, 1) though alkyl oxonium salts such as triethyl oxonium tetrafluoroborate 1 (known as Meerwein's reagent) have been utilized in organic synthesis as powerful alkylation reagents for alcohol or amine 2,3) ( Fig. 1). However, they are chemically unstable and sensitive to moisture, so they are difficult to handle. Recently, Mascal et al. reported the synthesis of oxatriquinane 2 and oxatriquinacene 3, which have a tricyclic condensed ring structure with an oxygen cationic center. 4)Compound 2 was isolated as a crystalline solid suitable for X-ray crystal structure analysis. Interestingly, 2 could be purified by column chromatography and was stable under reflux in alcohol or water. Subsequently, they synthesized several oxatriquinanes with simple alkyl groups and carried out X-ray crystal structure analysis.5,6) A unique S N 2 reaction at tertiary carbon in the α-position to the oxygen center was also reported.7) Most recently, oxatriquinane having a hydroxy group at the α-position to oxygen (4) was found to have the longest C-O bond length so far reported among organic compounds. 8)We became interested in these stable oxonium cation species, and set out to synthesize further examples for examination of their potential utility in materials science or medicinal chemistry.First, we focused on oxatriquinane having a simple ester group, to see whether such a group is compatible with the oxonium cation. As shown in Chart 1, the starting ketone 5, 7) which was synthesized from 1,5-cyclooctadiene, was subjected to Reformatsky reaction to afford β-hydroxyester 6 in good yield. Compound 6 was obtained as nearly a single stereoisomer, and its stereochemistry was determined by examination of the nuclear Overhauser effect (NOE) between methine proton at C1 and methylene protons at the α-position to the carbonyl group. Next, 6 was treated with trifluoromethanesulfonic acid (TfOH) in acetonitrile to give oxatriquinane trifluoromethanesulfonate, but we could not obtain this in crystalline form, so the salt was purified by simple anion exchange using sat. aqueous KPF 6 to afford oxatriquinane hexafluorophosphate 7 in an excellent yield as a stable off-white solid after usual work-up. Recrystallization from CH 2 Cl 2 /Et 2 O afforded colorless fine needles. Compound 7 showed good solubility in acetonitrile, dichlo...

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Section: Methodsmentioning

confidence: 99%

“…There have been few reports on stable organic oxonium salts, 1) though alkyl oxonium salts such as triethyl oxonium tetrafluoroborate 1 (known as Meerwein's reagent) have been utilized in organic synthesis as powerful alkylation reagents for alcohol or amine 2,3) (Fig. 1).…”

mentioning

confidence: 99%

Functionalized Oxatriquinanes and Their Structural Equilibrium in Protic Solvent

Suzuki

Muratake

2014

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…Triethyloxonium tetrafluoroborate (Et30BF 4 ) was prepared by the method of Meerwein et a/. 14 Chhoroform was washed with sulfuric acid, dilute aqueous sodium carbonate, and water successively, and dried over anhydrous sodium sulfate; distillation followed. bp 61 oc.…”

Section: Methodsmentioning

confidence: 99%

“…In Table IV (14) where a, {3, andy mean the relative peak areas of the corresponding acetal carbon signals in Figure 4, [A]; is the mole fraction of DOL in fractionated copolymers, which is evaluated from the 1 H NMR spectra, and the s.ubscript i is the fraction number. Figure 4 are equal within the experimental error and that the [AB] diad fraction of the original copolymer, 0.09 4 , which is determined from eq 5, is nearly equal to the [AB], diad fraction 0.077 , which is calculated from eq 19.…”

Section: Aa]=[a]-[ab] [Bb] =[B]-[ab]mentioning

confidence: 99%

Cationic Copolymerization of 1,3-Dioxolane with Tetrahydrofuran Initiated with Methyl Fluorosulfate

Yokoyama

Okada

Sumitomo

1979

Polym J

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ABSTRACT:Cationic copolymerization of 1,3-dioxolane (DOL) with tetrahydrofuran (THF) was carried out in chloroform at ooc with methyl fluorosulfate (CH30S02 F) and triethyloxonium tetrafluoroborate (Et30BF4 ) as initiators. The gas chromatographic determination of the residual monomers during the copolymerization revealed that both DOL and THF were consumed concurrently from the initial stage of the polymerization with CH30S02 F. With Et30BF4 , on the other hand, only THF was consumed at first, followed by the rapid consumption of DOL after an induction period. The fractionation of the reaction products and the microstructural analysis by 1 H and 13 C NMR spectroscopy showed that the products obtained with CH30S02F were real copolymers containing an appreciable ammount of cross-over diads, while those with Et30BF4 were block copolymers and/or mixtures of homopolymers. The structures and reactivities of the growing species in these two copolymerization systems are discussed on the basis of these findings. In a previous paper, 1 we reported kinetic studies on the cationic polymerization of I ,3-dioxolane (DOL) initiated with methyl fluorosulfate (CH 3 0S02 F) in deuteriochloroform, and concluded that the polymerization proceeded through an ester growing species, although the coexistence of an undetectable amount of oxonium ionic growing species can not be ruled out. This conclusion was drawn on the basis of a large negative value of the activation entropy [8S:= -42calmol-1 deg-1 ( -176 J k -1 mol-1 )], which is characteristic of dipole-dipole SN2 reactions producing ionic species, e.g., the Menschutkin reaction, together with 1 Hand 13 C NMR scpectral data of the reaction system. This paper describes the cationic copolymerization of DOL with THF which was undertaken in chloroform using two different initiators, CH 3 0S0 2 F and Et30BF4 , in order to make clear the reactivity of the ester growing species in the polymerization of DOL.The cationic copolymerization of DOL with THF using stable oxonium salts as initiators has been attempted by two research groups. 2 • 3 Yamashita et a/. 2 confirmed by the gas chromatographic determination of the unreacted monomers during the copolymerization initiated with Et30BF4 that preferential polymerization of THF occurred in the initial stage of the copolymerization, and that once DOL began to polymerize after an induction period, the polymerization of THF slowed down gradually and eventually ceased. However, it was resumed, although very slowly, after the polymerization of DOL reached the equilibrium conversion. Lyudvig et a/. 3 studied the same copolymerization with Et 3 0SbCI 6 as an initiator and they concluded that the propagating species of DOL, which are supposedly solvated by THF monomers, grow only by the addition of DOL monomers, in agreement with the results of Yamashita et a/. 2 It seems strange at first glance that DOL cannot copolymerize with THF, because both DOL 4 · 5 and THF 6 • 7 copolymerize with 3,3-bischloromethyloxacyclobutane (BCMO), and both growing speci...

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“…To test if pure = , =-disubstituted methyl ethers could be produced, reaction 3 using the simpler Grignard reagent of bromoethane was carried out (Table I). However, after a reflux period of 6 hours a 15% yield of the mono- temperature (16,19), and particularly at -80°, the mixed acetal (monosubstituted) product is obtained with total allylic rearrangement ( 2 0 ) . Table I), it was found initially that polymerization occurred.…”

Section: E E 3mentioning

confidence: 99%

Organometallics, part VII. The synthesis of α,α‐disubstituted methyl ethers by reaction of ethyldiphenylorthoformate with organomagnesium compounds

Poncini¹

1983

Bulletin des Soc Chimique

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The reaction conditions are investigated for the production of pure = , --disubstituted methyl ethers. in ether, under reflux conditions, yielded mixtures of mono-and disubstituted ethers; the former with total allylic transposition. Crotyl Grignard, at room temperature, gave only the monosubstituted mixed acetal. Acetylenic organomagnesiums produced high yields of pure = , Crotyl-and ethyl-magnesium bromides on reaction with ethyldiphenylorthoformate =-disubstituted methyl ethers when the solvent was dichloromethane. Methyl vinyl and isopropenyl vinyl organomagnesiums in THF gave only disubstituted ethers.are rationalized in terms of a mechanism incorporating a two-fold nucleophilic attack on the ethoxyphenoxycarbonium ion formed from the orthoformate by the organometallic anion, displacing two phenoxy groups to yield the =, =-disubstituted methyl ethers.

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Über tertiäre Carboxoniumsalze

Cited by 155 publications

References 14 publications

Functionalized Oxatriquinanes and Their Structural Equilibrium in Protic Solvent

Functionalized Oxatriquinanes and Their Structural Equilibrium in Protic Solvent

Cationic Copolymerization of 1,3-Dioxolane with Tetrahydrofuran Initiated with Methyl Fluorosulfate

Organometallics, part VII. The synthesis of α,α‐disubstituted methyl ethers by reaction of ethyldiphenylorthoformate with organomagnesium compounds

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