Benzyl alcohols, reactivity with phenyl

Certain classes of compounds are too reactive for the present method. Ethyl mandelate produced a racemic, protected phenyl glycine derivative. Benzylic alcohols with two methoxy groups (directly conjugating in the 2 and 4 positions) gave azide of 50% e.e. 

The ability of fluoro-2 -phosphanes to transform silyl ethers into fluorides was first observed during a study of the reactions of phosphorus pentafluoride and its derivatives R PF5 (n = 1, 2, 3 R = hydrocarbon group) with trimethylsilyl ethers. Subsequently, this reaction was proposed as a new method for the preparation of C-F compounds from silyl ethers or silicic acid esters with fluoro-A -phosphanes. Pentafluorophenyl-substituted fluoro-A -phos-phanes were found to react similarily, Other workers found that tctrafluoro(phenyl)-A -phos-phane. which was chosen as the most convenient reagent with regard to reactivity and stability, gave considerable amounts of elimination products, especially with primary and cyclic alcohols. Good yields of fluorinated products are obtained when stable carbocations can be formed at the site of substitution, such as in tertiary alcohols, but 2-phcnylethanol. benzyl alcohol and diphcnylmethanol, on the other hand, give only poor yields of fluorinated products ethers and polymers are the main products. ... 

Relatively little basic information has been published regarding the kinetics of phenol-formaldehyde intermediates, especially of phenols, methylol phenols, benzyl alcohol and benzylic ethers with isocyanates. Due to the fact that a typical resole contains both phenolic and benzylic hydroxyl groups, it was of interest to determine their reactivity toward isocyanates in the presence of various catalysts, as well as the effect of substitution on their reactivity. This investigation describes the kinetics of model phenols and model benzyl alcohols with phenyl isocyanate catalyzed with either a tertiary amine (dimethylcyclo-hexylamine, DMCHA) or an organotin catalyst, dibutyltin dilaurate (DBTDL) in either dioxane or dimethylformamide solution. 

The reactivity of the model phenols and benzyl alcohols with phenyl isocyanate was determined in the presence of a tertiary amine (DMCHA) and a tin catalyst (DBTDL) by measurement of the reaction kinetics. The experimental results based on initial equal concentrations of phenyl isocyanate and protic reactants showed that the catalyzed reactions followed second order reaction with respect to the disappearance of isocyanate groups (see Figure 1). It was also found that a linear relationship exists between the experimental rate constant kexp, and the initial concentration of the amine catalyst (see Figure 2). In the case of the tin catalyst, the reaction with respect to catalyst concentration was found to be one-half order (see Figures 3-4). A similar relationship for the tin catalyzed urethane reaction was found by Borkent... 

The effect of type of catalyst on the reactivity of phenol and benzyl alcohol with phenyl isocyanate can be seen in Table III. In the case of tertiary amine (DMCHA), there is a relatively small difference in the reactivity of both the phenol and benzyl alcohol with phenyl isocyanate. Using DBTDL as catalyst, benzyl alcohol was found to be 26 times more reactive than phenol in the reaction with phenyl isocyanate. 

EFFECT OF SUBSTITUTION ON REACTIVITY OF MODEL BENZYL ALCOHOLS WITH PHENYL ISOCYANATE IN DIOXANE AT 25°C... 

EFFECT OF CATALYSTS ON THE REACTIVITY OF PHENOL BENZYL ALCOHOL AND ETHYL ALCOHOL WITH PHENYL ISOCYANATE... 

It is not intended to extend this discussion of reactions of carbocations with water to consideration of the alcoholic solvents trifluoroethanol (TFE) and hexa-fluoroisopropanol (HFIP), which have been extensively studied and reviewed by McClelland and Steenken.3 However, an important point of interest of these solvents is that their reactivities toward carbocations are greatly reduced compared with water (by up to a factor of 104 in TFE and 108 in HFIP) and that differences in rate constants can be observed between cations which would react indiscriminately at the solvent relaxation limit in water. The following comparisons of rate constants for carbocations with similar pAR values reacting with hexafluoroiso-propanol241,242 reinforces the conclusion that structural variations in the cation lead to changes in intrinsic barrier and, for example, that phenyl substitution is probably associated with such an increase in going from benzyl to benzhydryl (although the benzyl cation itself is not shown). 

Syntheses of alkyl phenyl ethers, C,H, OR, are carried out by refluxing aqueous or alcoholic solutions of alkali phenolates with alkyl halides the yields vary with the nature of the alkyl halides (40-80%). The reactive halogen in benzyl halides is easily replaced by an alkoxyl group (95%). ° The choice of a solvent is sometimes important. Thus, in the preparation of the alkyl ethers of o- and p-hydroxybiphenyl from a mixttire of the phenol, alkyl halide, and powdered potassium hydroxide, high yields are obtained using acetone as a solvent, whereas, with alcohol as solvent, only small yields are obtained. Triarylmethyl chlorides react with alcohols directly (97%). ... 

Other a-halogenated compounds have been used with equal success. These include iodoacetamide (140,144,141, 34,68,32), iodo ethyl alcohol (143), a brom fatty acids, and benzyl and phenyl ethyl halides (142). All react with certain SH groups of proteins at pH 7.0-9.0 and physiological temperatures. The iodoacetamide is somewhat more reactive than iodoacetate (144). Both iodoacetate and the corresponding amide were found to react fairly rapidly with p3rridine, even at pH 6.9 and 30 C. (145). Anson and Stanley (68) have reported that after almost complete inactivation of tobacco mosaic virus with iodoacetamide they could detect little, if any, drop in the number of SH groups. This calls for further study. 

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