Benzylic compound

Ingold and his co-workers used the competitive method in their experiments, in which nitration was brought about in acetic anhydride. Typically, the reaction solutions in these experiments contained o-8-I 4 mol of nitric acid, and the reaction time, depending on the reactivities of the compounds and the temperature, was 0-5-10 h. Results were obtained for the reactivities of toluene, > ethyl benzoate, the halogenobenzenes, ethyl phenyl acetate and benzyl chloride. Some of these and some later results are summarized in table 5.2. Results for the halogenobenzenes and nitrobiphenyls are discussed later ( 9.1.4, lo.i), and those for a series of benzylic compounds in 5,3.4. 

TABLE 5.9 Orientation in the nitration of some benzylic compounds... 

In a later paper Knowles and Norman compared more fully nitrations of benzylic compounds in acetyl nitrate and in mixed acid (table 5.9), and interpreted the results in terms of three factors nitronium ion nitration in both media some degree of protonation of the oxygen... 

Treatment of 3-hydroxy-l,2-benzisoxazole with benzyl bromide gave a mixture of O-and iV-benzyl compounds. The iV-benzyl compound gave a benzoxazin-4-one on reaction with base, via the intermediates shown in Scheme 88 (78CPB549). 

For the lithiation of the majority of less acidic a-hetero-substituted benzylic compounds there is a good chance that one of the following base systems is applicable at — 70 °C ... 

Recently some information became available on a new type of highly active one-component ethylene polymerization catalyst. This catalyst is prepared by supporting organometallic compounds of transition metals containing different types of organic ligands [e.g. benzyl compounds of titanium and zirconium 9a, 132), 7r-allyl compounds of various transition metals 8, 9a, 133), 7r-arene 134, 185) and 71-cyclopentadienyl 9, 136) complexes of chromium]. 

Removal of solvent from the extracts leaves a residue that is purified by dry-column chromatography.2 The residue is dissolved in 40 ml. of acetone in a 300-ml., round-bottomed flask, 30 g. of silica gel (Note 8) is added, and the acetone is removed with a rotary evaporator. The resulting solid mixture is placed on top of 360 g. of dry silica gel (Note 8) packed in flexible nylon tubing (Note 9), and the column is developed with 420 ml. of 10 1 (vjv) benzene-acetone. Approximately 150 ml. of solvent drips from the bottom of the column toward the end of development, and this eluent is collected in 25-ml. fractions and checked for product by thin layer chromatography (Note 10). The column itself is then cut into 2-cm. sections, the silica gel in each section is eluted with three 25-ml. portions of ethyl acetate, and the eluent from each section is analyzed by thin-layer chromatography (Note 10). Combination of all the product-containing fractions yields 1.2-1.5g. (40-47%) of the benzylated compound as an oil, n 1.6083 (Notes 11 and 12). 

As far as the reactions with benzyl chlorides are concerned (74), the oxidative addition of benzyl chloride and substituted benzyl chlorides to palladium atoms yields rj -benzylpalladium chloride dimers. The parent compound, bis(l,2,3-7 -benzyl)di-/i,-chloro-palladium(II), quantitatively adds four molecules of PEts by first forcing the rj -benzyl-iy -benzyl transformation, with subsequent breakage of the Pd-Cl bridges to form trans-bistPEtsKbenzyDchloroPddI). The spectral characteristics of the parent molecule are indicative of the allylic type of bonding. Similar i7 -benzyl compounds were formed from 4-methylbenzyl chloride, 2-chloro-l,l,l-trifluoro-2-phenylethane, and 3,4-dimethylbenzyl chloride. 

Cyanation of ketones, nitro compounds, or benzylic compounds... 

Aromatic rings are also tolerated in the side chain, as demonstrated by Krishnamurthy et al. [109]. The l, l -dimethylbenzyl compound (117) showed higher binding affinity than the simple benzyl compound (116). Compound (117) also showed around 13-fold selectivity for CB2 over CBi binding. 

Subsequently, other members of the family of siienes (Me3Si)2Si= C(OSiMe3)R have been prepared, where R = Me, Et, i-Pr, CH2Ph, bicyclooctyl, CEt3, 1-methylcyclohexyl, and Mes. The first four siienes listed were not stable in inert solvents, and hence were not observable by NMR spectroscopy, since they rapidly reacted intermolecularly to give linear and/or cyclic head-to-head dimers.87 This is illustrated in Eq. (14) for the benzyl compound where the initially formed silene 5 yielded the cyclic head-to-head dimer 6 as well as the linear head-to-head dimer 7. The latter four siienes were all relatively stable and were characterized by NMR spectroscopy.105... 

In some cases, such as the isopropyl or benzyl compounds in Eq. (27), both the cyclic [2 + 2] dimer and the linear dimer were formed in appreciable amounts.86... 

Benzyl and Allyl Carbon Atoms Hydrogenolysis of a carbon-heteroatom bond is extremely fast if the heteroatom is connected to allylic or benzylic carbon atoms. The benzylic compounds are used very frequently in organic chemistry as protecting groups. Because of its great importance the benzylic compounds are discussed separately in the next section. 

In spite of the successful application of catalytic transfer hydrogenolysis in the case of benzylic compounds, this method is not suitable for the cleavage of the allylic C-O bonds. 

See Other BENZYL COMPOUNDS, NITROBENZYL COMPOUNDS, NITROARYL COMPOUNDS... 

See other gas evolution incidents, molecular sieve incidents, polycondensation REACTION INCIDENTS See other benzyl compounds... 

See other benzyl compounds, polycondensation reaction incidents... 

See entry alkyl nitrates See other BENZYL compounds 2766. 3-Methyl-4-nitrophenol... 

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