Deuterated Olefins from the Wittig Reaction

Malloy, Thomas B.; Hedges, Richard M.; Fisher, Farley

doi:10.1021/jo00837a634

“…Upon treatment with nondeuterated PS at 0 °C, a 1:1.06 mixture of hexadeuterated methylidenecyclopentane ( 6 )7 and 1 in CD 2 Cl 2 (toluene, [D 8 ]toluene as internal reference) was isomerized into a mixture of nondeuterated and partially deuterated 1‐methylcyclopentenes. The 2 H{ 1 H}‐NMR spectrum of the mixture displayed three signals for the methyl group corresponding to CH 2 D, CHD 2 , and CD 3 with relative integrations of 1.31:1.93:1 (Figure 1).…”

Section: Methodsmentioning

confidence: 99%

Polysulfones: Catalysts for Alkene Isomerization

Marković

¹

,

Vogel

²

2004

Angewandte Chemie

3

0

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It has long been known that alkenes can be isomerized by sulfur dioxide. The process is generally explained by invoking an ene reaction between an SO 2 molecule and the alkene to give a b,g-unsaturated sulfinic acid intermediate (e.g. 1 + SO 2 !2; Scheme 1), which then undergoes a [1,3] sigmatropic shift to form an isomeric b,g-unsaturated sulfinic acid (2!3), followed by a retro-ene reaction that eliminates SO 2 (3!4 + SO 2 ).[1]When we treated methylidenecyclopentane (1) with various amounts of SO 2 in CD 2 Cl 2 at 0 8C, isomerization into 1-methylcyclopentene (4) occurred within a few hours. However, in the presence of a small amount of CH 2 I 2 , the reaction was totally inhibited. As 1,1-diodoalkanes in the presence of SO 2 are suspected to generate iodine radicals, [2] this striking observation suggests that the SO 2 -promoted isomerization 1!4 does not follow the generally accepted mechanism 1!2!3!4, but rather another mechanism that involves radical intermediates. This hypothesis was confirmed by the observation that TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy free radical) and Bu 3 SnH both efficiently inhibit the SO 2 -promoted isomerization 1!4. In the absence of radicalscavenging agents, the kinetics of the SO 2 -promoted isomerization 1!4 showed an induction period, the duration of which increased upon decreasing the SO 2 concentration. This period was followed by a zeroth-order reaction until about 70 % conversion. During the induction period a white precipitate formed, the amount of which increased upon Scheme 1. General mechanism for SO 2 -catalyzed isomerization of methylidenecyclopentane (1).

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“…The tetradeuterio compound 13 was prepared by the methods outlined in Scheme 1. The synthesis of 14 was achieved from the acetal (22) as outlined in Scheme 2. The ketone (23) in Scheme 2 was produced in a substantially improved yield over that reported earlier (11) by periodate oxidation under carefully buffered conditions.…”

Section: Synthesismentioning

confidence: 99%

“…A mixture of 5-amino-5-(hydroxymethyl)-2-phenyl-l,3-dioxan (70.6 g, 0.338 mol) (22) and pH 6 buffer solution (2.0 L) in a 3-L roundbottomed flask was stirred mechanically at room temperature. The reaction mixture initially became homogeneous when sodium metaperiodate (72.3 g, 0.338 mol) was added all at once with vigorous stirring.…”

Section: -0~0-2-phenyl-l3-dioxan (23)mentioning

confidence: 99%

“…The 100 MHz 'Hmr spectrum TMS (CDC13) showed 6: 4.47 singlet, 4H), 5.87 (singlet, lH), and 7.42 (complex multiplet, 5H). -2-phenyl-1,3-dioxan-7,7-dz (24) The procedure was a modification of that of Malloy et al (22). A 3-L three-necked round-bottomed flask was fitted with a reflux condenser, a dropping funnel, a mechanical stirrer, and a gas inlet tube.…”

Section: -0~0-2-phenyl-l3-dioxan (23)mentioning

confidence: 99%

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Secondary deuterium isotope effects on both rate and product determining steps in the thermolysis of 4-methylene-1-pyrazoline

Chang¹,

Crawford²

1981

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The secondary deuterium kinetic isotope effect in the thermolysis of 4-methylene-1-pyrazoline and four of its deuterated isomers has been studied. The value of δΔG≠/n is 142 cal mol−1 if it is a single C—N cleavage process or 71 cal mol−1 if it is a concerted rupture of two C—N bonds. The product distributions can only be rationalized in terms of a mechanism involving a rate determining C—N bond rupture to form a diazenyl diradical intermediate which then can close to methylenecyclopropanes by three possible modes. This requires a secondary isotope effect in the product determining step of 1.33 ± 0.05, for the rotation of CH2 (CD2) out of the plane of the allylic radical in the intermediate.

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“…Upon treatment with nondeuterated PS at 0 8C, a 1:1.06 mixture of hexadeuterated methylidenecyclopentane (6) [7] and 1 in CD 2 Cl 2 (toluene, [D 8 ]toluene as internal reference) was isomerized into a mixture of nondeuterated and partially deuterated 1-methylcyclopentenes. The 2 H{ 1 H}-NMR spectrum of the mixture displayed three signals for the methyl group corresponding to CH 2 D, CHD 2 , and CD 3 with relative integrations of 1.31:1.93:1 (Figure 1).…”

mentioning

confidence: 99%

Polysulfones: Catalysts for Alkene Isomerization

Marković

¹

,

Vogel²

2004

View full text Add to dashboard Cite

It has long been known that alkenes can be isomerized by sulfur dioxide. The process is generally explained by invoking an ene reaction between an SO 2 molecule and the alkene to give a b,g-unsaturated sulfinic acid intermediate (e.g. 1 + SO 2 !2; Scheme 1), which then undergoes a [1,3] sigmatropic shift to form an isomeric b,g-unsaturated sulfinic acid (2!3), followed by a retro-ene reaction that eliminates SO 2 (3!4 + SO 2 ).[1]When we treated methylidenecyclopentane (1) with various amounts of SO 2 in CD 2 Cl 2 at 0 8C, isomerization into 1-methylcyclopentene (4) occurred within a few hours. However, in the presence of a small amount of CH 2 I 2 , the reaction was totally inhibited. As 1,1-diodoalkanes in the presence of SO 2 are suspected to generate iodine radicals, [2] this striking observation suggests that the SO 2 -promoted isomerization 1!4 does not follow the generally accepted mechanism 1!2!3!4, but rather another mechanism that involves radical intermediates. This hypothesis was confirmed by the observation that TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy free radical) and Bu 3 SnH both efficiently inhibit the SO 2 -promoted isomerization 1!4. In the absence of radicalscavenging agents, the kinetics of the SO 2 -promoted isomerization 1!4 showed an induction period, the duration of which increased upon decreasing the SO 2 concentration. This period was followed by a zeroth-order reaction until about 70 % conversion. During the induction period a white precipitate formed, the amount of which increased upon Scheme 1. General mechanism for SO 2 -catalyzed isomerization of methylidenecyclopentane (1).

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Deuterated Olefins from the Wittig Reaction

Cited by 18 publications

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Polysulfones: Catalysts for Alkene Isomerization

Polysulfones: Catalysts for Alkene Isomerization

Secondary deuterium isotope effects on both rate and product determining steps in the thermolysis of 4-methylene-1-pyrazoline

Polysulfones: Catalysts for Alkene Isomerization

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