Chemical reactions under high pressure. XXII. Effect of pressure on the allylation of hindered phenoxides

Noble, W. J. Le; Hayakawa, Tadao; Sen, A. K.; Tatsukami, Yoshiharu

doi:10.1021/jo00800a039

Cited by 14 publications

(4 citation statements)

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“…2,6-Diethylphenol. 43 Three grams (20 mmol) of 2,6diethylaniline was dissolved in 60 mL of water and 40 mL of concentrated sulfuric acid in a 1 L round-bottom flask with a stir bar. Twenty-five grams of ice was added, and the solution was immersed in an ice bath.…”

Section: Methodsmentioning

confidence: 99%

Antihydrophobic Cosolvent Effects for Alkylation Reactions in Water Solution, Particularly Oxygen versus Carbon Alkylations of Phenoxide Ions

2002

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Antihydrophobic cosolvents such as ethanol increase the solubility of hydrophobic molecules in water, and they also affect the rates of reactions involving hydrophobic surfaces. In simple reactions of hydrocarbons, such as the Diels-Alder dimerization of 1,3-cyclopentadiene, the rate and solubility data directly reflect the geometry of the transition state, in which some hydrophobic surface becomes hidden. In reactions involving polar groups, such as alkylations of phenoxide ions or S(N)1 ionizations of alkyl halides, cosolvents in water can have other effects as well. However, solvation of hydrophobic surfaces is still important. By the use of structure-reactivity relationships, and comparing the effects of ethanol and DMSO as solvents, it has been possible to sort out these effects. The conclusions are reinforced by an ab initio computer model for hydrophobic solvation. The result is a sensible transition state for phenoxide ion as a nucleophile, using its oxygen n electrons to avoid loss of conjugation. The geometry of alkylation of aniline is very different, involving packing (stacking) of the aniline ring onto the phenyl ring of a benzyl group in the benzylation reaction. The alkylation of phenoxide ions by benzylic chlorides can occur both at the phenoxide oxygen and on ortho and para positions of the ring. Carbon alkylation occurs in water, but not in nonpolar organic solvents, and it is observed only when the phenoxide has at least one methyl substituent ortho, meta, or para. The effects of phenol substituents and of antihydrophobic cosolvents on the rates of the competing alkylation processes indicate that in water the carbon alkylation involves a transition state with hydrophobic packing of the benzyl group onto the phenol ring. The results also support our conclusion that oxygen alkylation uses the n electrons of the phenoxide oxygen as the nucleophile and does not have hydrophobic overlap in the transition state. The mechanisms and explanations for competing oxygen and carbon alkylations differ from previous proposals by others.

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Section: Methodsmentioning

confidence: 99%

Antihydrophobic Cosolvent Effects for Alkylation Reactions in Water Solution, Particularly Oxygen versus Carbon Alkylations of Phenoxide Ions

2002

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“…46°C (ref. [26] 52-53°C [16] A solution of 17 (3 g, 12.6 mmol) in anhydrous Et 2 O (120 mL) was added dropwise to a suspension of LiAlH 4 (1.19 g, 31.5 mmol) in anhydrous Et 2 O (60 mL) at 0°C under Ar. The reaction mixture was allowed to react at room temp.…”

Section: General Proceduresmentioning

confidence: 99%

Syntheses of Sterically Hindered Pyridinium Phenoxides as Model Compounds in Nonlinear Optics

et al. 2006

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Noncentrosymmetric molecules with a π-conjugated system and, among them, push-pull molecules such as pyridinium phenoxide, are a promising new class of materials for applications in optoelectronics due to their nonlinear optical (NLO) properties. Modelling studies have indicated that an increase in the twist angle between the two aromatic rings leads to an enhancement of the NLO properties. In order to

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“…Neither did this investigation achieve any conclusive results in alkylation reactions of the phenoxides. 26 In order to explain these seemingly contradictory results, we began investigating steric effects for other classes of reaction in which electrostriction should barely take place. This was done by measuring the influence of pressure and extracting the volumes of activation of reactions involving hindered transition states.…”

Section: E = Ef+et+eo+evmentioning

confidence: 99%

The pressure effect on strained transition states. Correlation between strain and volume of activation: mechanistic and synthetic involvements

Jenner¹

1985

J. Chem. Soc., Faraday Trans. 1

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This paper considers the description of the pressure effect on strained transition states and proposes a kinetic formalism based on the concept of steric or strain volume of activation with a view to devising models allowing the calculation of structure effects on the position of the transition state along the reaction coordinate. The applicability of the equation is examined for several reactions (Menshutkin, solvolysis and hydrogen transfer). When steric or strain factors operate in a given reaction the pressure effect is more marked than in an unhindered analogue. Possible consequences of this phenomenon are considered, with special emphasis on mechanistic and synthetic implications at high pressure.

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Chemical reactions under high pressure. XXII. Effect of pressure on the allylation of hindered phenoxides

Cited by 14 publications

References 0 publications

Antihydrophobic Cosolvent Effects for Alkylation Reactions in Water Solution, Particularly Oxygen versus Carbon Alkylations of Phenoxide Ions

Antihydrophobic Cosolvent Effects for Alkylation Reactions in Water Solution, Particularly Oxygen versus Carbon Alkylations of Phenoxide Ions

Syntheses of Sterically Hindered Pyridinium Phenoxides as Model Compounds in Nonlinear Optics

The pressure effect on strained transition states. Correlation between strain and volume of activation: mechanistic and synthetic involvements

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