Phenyl compounds

The acid cleavage of the aryl— silicon bond (desilylation), which provides a measure of the reactivity of the aromatic carbon of the bond, has been applied to 2- and 3-thienyl trimethylsilane, It was found that the 2-isomer reacted only 43.5 times faster than the 3-isomer and 5000 times faster than the phenyl compound at 50,2°C in acetic acid containing aqueous sulfuric acid. The results so far are consistent with the relative reactivities of thiophene upon detritia-tion if a linear free-energy relationship between the substituent effect in detritiation and desilylation is assumed, as the p-methyl group activates about 240 (200-300) times in detritiation with aqueous sulfuric acid and about 18 times in desilylation. A direct experimental comparison of the difference between benzene and thiophene in detritiation has not been carried out, but it may be mentioned that even in 80.7% sulfuric acid, benzene is detritiated about 600 times slower than 2-tritiothiophene. The aforementioned consideration makes it probable that under similar conditions the ratio of the rates of detritiation of thiophene and benzene is larger than in the desilylation. A still larger difference in reactivity between the 2-position of thiophene and benzene has been found for acetoxymercuration which... 

Treatment of 7-acetamido-2,4-dimethyl-l,8-naphthyridine (139 R = NHAc, R = Me) with ethyl iodide at 110° for 24 hr gave an ethiodide the corresponding 4-phenyl compound and methyl iodide formed a methiodide. Both of these salts possess a reactive methyl group and are therefore the 1-salts (cf. 140). The easily formed... 

Phenyl-jodidchlorid, n. phenyl iodochloride, -milchsaure, /. phenyllactic acid, -saure, /. phenylic acid (phenol, CeHaOH). -schwefel-saure, /. phenylsulfuric acid, -senfol, n. phenyl mustard oil. -siliciumchlorid, n. trichlorophenylsilane, CaHiSiCla. -verbindung, /. phenyl compound, -wasserstoff, m. phenyl hydride, benzene. 

The 3-phenyl derivative 3a was similarly obtained by cyclodehydration of O-phenacylsalicylam-ide.33 An analogous reaction of O-acetonylsalicylamide gives 3-methyl-l,4-benzoxazepin-5(4//)-one (3b).34 The 2-phenyl compound can also be obtained from the corresponding salicylamide derivative in 56% yield.420... 

Of simple 1,5-benzothiazepines, only the 2-unsubstituted or 2-phenyl-substituted 4-methoxy-1,5-benzothiazepines are known. X-ray crystallography of the phenyl compound shows that the seven-membered ring exists in a boat form.51... 

Thiazolo[3,2-/>][l,2,4]triazoles are often sufficiently reactive to be brominated in the thiazole nucleus (see also B,5). Thus, although the unsubstituted substrate and the 2-phenyl and 2-methyl derivatives would not react with NBS in refluxing chloroform, the 5-methyl, 2,5-dimethyl, and 5-methyl-2-phenyl compounds gave 6-bromo products (71JAP71/26498 74JHC459). 

The wide variation in the entropy factors for both the substituted phenyl and heterocyclic compounds and in particular for the methoxyphenyl and furan derivatives was considered to be strong evidence for solvent effects being predominant in determining the activation entropy. Consequently, discussion of the substituent effects in terms of electronic factors alone requires caution in this reaction. Caution is also needed since rates for the substituted phenyl compounds were only determined over a 20 °C range. The significance of entropy factors has also been indicated by the poor correlation of the data of the electrophilic reactivities of the heterocyclic compounds, as derived from protodemercuration, with the data for other electrophilic substitutions and related reactions572. 

Rate coefficients and kinetic parameters for iododeboronation were determined for the benzene- and thiophene-boronic acids, and the results are given in Table 256. The relative reactivities derived from this work correlated well with those obtained in a number of other electrophilic substitutions572, which is perhaps surprising in view of the large variation in the entropies of activation. These differences were explained by Brown et al.132 in terms of the transition state for the phenyl compound occurring earlier along the reaction coordinate than for the... 

It is shown by Grossmann that for his phenyl compounds the results are qualitatively the same in the presence and in the absence of strong radiation doses, yet the results of Nowak and various others show that for alkyl metals radiation effects are more important. 

Complexes of the type RMn(CO)5, where R is a primary alkyl group, undergo facile CO insertion at room temperature. Carbonylated to the corresponding acyls have been the pentacarbonyls with R = Me 50, 69), Et 51, 70), n-Pr 51), and CHjSiMe, 243). The phenyl compound, PhMn(CO)j, also inserts CO, but the benzyl analog does not 51). The claim 194) that CX3Mn(CO)5 (X = H, D, or F) converts to CX3COMn-(CO) ( < 5) upon irradiation in an Ar matrix at 17°K has been disputed 209). Carbon monoxide dissociation and recombination have been proposed instead for MeMn(CO)5. 

The Taft relation Ej 2 = P 2a + x, which was found to hold for organic compounds and some transition metal complexes can also be of use here (37). Phenyl compounds do not fit the relation. This is probably due to a mesomeric effect that depends on the dihedral angle between the phenyl and the NCS2 planes. For bulky substituents deviations are also found which could be caused by widening of the CNC angle, changing the hybridisation of the N. The low values of p indicate that the M.O. s involved in the electron transfer have little ligand contribution. 

Silylation of the silsesquioxane [(C6H11)7Si709(0H)3] (see Section IV,E for its structure) leads to disilanols [(C6Hn)7Si709(0H)2SiMe2R] (R = Me or Ph). The structure of the phenyl compound 59 shows the... 

The spectrum of the ester 73c is similar to that of the unsubstituted phenyl compound 73e (both not shown). It is noted that the chemical shift of the HC8 reflects the electron-withdrawing properties of the substituents. A combination of ID and 2D techniques is used to establish the assignments shown, and the chemical shift changes as compared to /J,/J-carotene are listed in Tables 22 and 23. 

Despite their importance in many pharmacological uses and potential applications, solubilities of hydroxypyranones, hydroxypyridinones, and their complexes have not been extensively and systematically investigated and established. This situation contrasts sharply with that for partition coefficients, as will become apparent in the following section. The solubility of maltol in water is approximately 0.1moldm , of ethyl maltol 0.13 mol dm, at 298 K. 1,2-Alkyl-3-hydroxy-4-pyridinones show the expected decrease in water-solubility as the sizes of the alkyl groups increase solubilities - in water at 298 K - of l-aryl-2-methyl-3-hydroxy-4-pyridinones decrease from 9 X 10 mol dm for the 1-phenyl compound through 6 x lO- moldm for l-(4 -tolyl) to 6 x 10 mol dm for l-(4 -re-hexyl-phenyl) (37). 

In contrast to the alkyl substituted polymers, the P-phenyl compounds, [Ph(Me)PN]n and [Ph(Et)PN]n are brittle, brown colored materials which are quite soluble in THF and are readily plasticized by trace amounts of solvent. Determination of molecular weight... 

In analogy with 143d, the 2-phenyl compound is obtained from tropone and 3-phenylsydnone in a low yield [93JCS(P1)1617]. The cycloaddition proceeds peri- and regioselectively in a [4it + 2tt] mode followed by extrusion of carbon dioxide from the primary adduct and spontaneous dehydrogenation. 

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