Phenyl compounds unsubstituted

Whereas reaction of hydrazones disubstituted in the 4,5-position of the selenazole rings with diazotized arylamines only gives formazans, compounds unsubstituted in the 5-position can be attacked there by the diazonium cation. In fact, the azo coupling in this position is decidedly quicker reaction of 5-benzylidenehydrazino-4-phenyl-... 

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 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. 

The stability of the ring system decreases considerably when one hydrogen atom is left unsubstituted (55 b). It has been claimed that 5-monosubstituted oxadiazoles like XLII could not exist, as it was not possible to isolate the 5-phenyl derivative by decarboxylation of the corresponding acid or by hydrolyzing the 3-benzoyl-5-phenyl compound. 

The presence of a phenoxy or a substituted phenoxy group at the 5-position of the oxadlazolone ring yields molecules that possess low level activity on aphids in the primary screen. The most active compound is the unsubstituted phenyl molecule (TIm20), and any other substituent on the phenyl ring (2F, 4-C1 or 3,4,5-CHj) reduces the activity on aphids compared to the unsubstituted phenyl compound. See Table 4. 

Most of the 5-unsubstituted compounds are particularly reactive, and special care must be taken during their synthesis (386). Thus the synthesis of 2-phenyl-/i-2 thia2oline-4-one has been claimed several times, and... 

The original acid—clay developers have been largely replaced by phenohc compounds, such as para-substituted phenohc novolaks. The alkyl group on the phenohc ring is typically butyl, octyl, nonyl, or phenyl. The acidity is higher than that of a typical unsubstituted novolak because of the high concentration of 2,2 -methylene bridges. 

Benzisoxazole and its simple alkyl derivatives are liquids with b.p. s of 84°C/11 mmHg for the unsubstituted system, 92.5°C/11 mmHg for the 3-methyl compound, and 117 °C/11 mmHg for the 4,6-dimethylbenzisoxazole. 2,1-Benzisoxazole is also a liquid, b.p. 94.4-94.5 °C/11 mmHg, and its 3-methyl derivative has a b.p. of 115.5-116 °C/11 mmHg. Introduction of a 3-phenyl substituent in both systems results in crystallinity, with m.p. s of 83-84 °C and 52-53 °C, respectively. Polar substituents, as anticipated, also impart crystallinity to these systems. 

Knorr reported the first pyrazole derivative in 1883. The reaction of phenyl hydrazine and ethylacetoacetate resulted in a novel stmcture identified in 1887 as l-phenyl-3-methy 1-5-pyrazolone 9. His interest in antipyretic compounds led him to test these derivatives for antipyretic activity which led to the discovery of antipyrine 10. He introduced the name pyrazole for these compounds to denote that the nucleus was derived from the pyrrole by replacement of a carbon with a nitrogen. He subsequnently prepared many pyrazole analogs, particularly compounds derived from the readily available phenyl hydrazine. The unsubstituted pyrazole wasn t prepared until 1889 by decarboxylation of liT-pyrazole-3,4,5-tricarboxylic acid. ... 

Studies of chlorination and bromination of 2//-cyclopenta[reactivity differences dependent on substituents and halogenation conditions. In monochlorination the unsubstituted compound was more reactive than its 2-methyl and 2-phenyl derivatives, the reactivity ratio being 7.1 1.7 1 [78H(11)155]. Chlorination occurred most readily in the 5- and 7-positions of the cyclopentadienyl moiety, but once all three positions had been substituted, NCS attacked the methyl group... 

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