Alkyl aryl methanones

Chemistry. The majority of the alkyl aryl methanone oxime ethers were synthesized as shown in Figure 1. The alkyl aryl methanones were prepared by either of two methods. In the first method, the appropriately-substituted benzonitrile was treated with the desired alkylmagnesium halide to give the desired ketone(8). 

The second approach involved the appropriately substituted benzoic acid and conversion to the acid chloride. Subsequently, the acid chloride is treated with 0,N-dimethylhydroxylamine hydrochloride ). This methoxymethylbenzamide is treated with an alkylmagnesium halide to give the alkyl aryl methanone. These ketones were purified by distillation. 

The ketones were converted to the E,Z-alkyl aryl methanone oximes by a variety of methods. Most commonly, the ketone and hydroxylamine hydrochloride were suspended in ethanol and two equivalents of pyridine added. After isolation, the oximes were treated with anhydrous hydrogen chloride gas to give the hydrogen chloride salt of the -alkyl aryl methanone oxime(101. The resulting salt was treated with dilute sodium bicarbonate to yield the desired E-alkyl aryl methanone oxime. Earlier literature reports indicated that E-aldoxime was converted to the Z-aldoxime under similar conditions(11). 

The alkyl aryl methanone oximes can be converted to oxime ethers by several methods. The usual alkylation procedure utilized was a phase transfer catalyzed alkylation wherein the E-alkyl aryl... 

Figure 1. Synthesis of Alkyl Aryl Methanone Oxime Ethers.

In this work it was reported that the biological activity and residual properties of biphenyl-3-ylmethyl (1R,S)-cis-3-(2,2-di-chlorovinyl)-2,2-dimethylcyclopropanecarboxylate were about one-half that of the corresponding 3-phenoxybenzyl ester. The preparation of a series of substituted derivatives of biphenyl-3-ylmethyl (1R,S)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-carboxylates resulted in esters with significantly greater insecticidal activity and broader spectrum of biological activity than the conventional pyrethroid insecticides(7). The 2-monosubstituted derivatives were found to be the most active compounds in this series with the 2-methyl compound being the most active. This result encouraged us to combine these biphenyl-3-ylmethyl compounds with alkyl aryl methanone oximes. 

The replacement of the ester linkage of pyrethroids by alternatives was known to lead to compounds of diminished biological activity. Thiol esters and amides are two such isosteric replacements that lead to a loss in biological activitv(13.14). The exception to this trend was the replacement by the oxime function-alitv(2.3). The alkyl aryl oxime ethers are not susceptible to alkaline hydrolysis and esteric attack as are the pyrethroid esters(15). The present study details our investigation of the biological activity of [1,1 -biphenyl]-3-methanols when combined with alkyl aryl methanone oximes. 

Alkyl aryl methanone oxime ethers QSAR analysis, 183 insecticidal activity, 175-176 structure-activity relationships, 183-185 synthesis, 174-178... 

E,Z-Alkyl aryl methanone oximes, 176 Alkyl aryl methanones, 176 Alkyl aryl oxime ethers combined with alcohols, 182... 

Next, the effect on activity with respect to the size of the alkyl group in our series compared to that disclosed in the literature (2,4) was of interest. The effectiveness of alkyl groups is reported to be cyclopropyl > isopropyl > ethyl > methyl. In fact, this trend was followed in the [1,1 -biphenyl]-2-methyl-3-methanol derived alkyl aryl oxime ethers. This is illustrated with the (E,Z)-4-trifluoromethoxyphenyl(alkyl)methanone oxime ethers, Compounds 14, 16, 19 (Table V). The activity of this series increases with increasing size of the alkyl group. However, when cyclobutyl was incorporated, activity was lost. The cyclopropyl was the most effective while the isopropyl group was somewhat less effective. Other alkyl changes resulted in a rapid loss of activity. 

Diaryl ketones do not undergo photodissociation in the same way as alkyl ketones, probably because cleavage to phenyl and other aryl radicals is unfavorable (Table 4-6). Nevertheless, aromatic ketones are photochemically reactive in the presence of compounds that can donate a hydrogen atom, with the result that the carbonyl group is reduced. Indeed, one of the classic photochemical reactions of organic chemistry is the formation of 1,1,2,2-tetraphenyl-1,2-ethanediol (3, benzopinacol) by the action of light on a solution of diphenyl-methanone (2, benzophenone) in isopropyl alcohol. The yield is quantitative. 

Aromatic ketones may contain one aryl ring and one alkyl chain, such as acetophenone (2), or two aryl rings such as benzophenone (diphenyl-methanone, 4), Molecules containing a carbonyl group in a side chain show normal aliphatic behaviour and are not considered here. Aromatic ketones generally behave in a similar manner to aldehydes (see Scheme 6.9) but are slightly less reactive. 

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