Benzyl alcohol double

Section 1115 The simplest alkenylbenzene is styrene (C6H5CH=CH2) An aryl group stabilizes a double bond to which it is attached Alkenylbenzenes are usu ally prepared by dehydration of benzylic alcohols or dehydrohalogena tion of benzylic halides... 

Previous studies by Sorokin with iron phthalocyanine catalysts made use of oxone in the oxidation of 2,3,6-trimethylphenol [134]. Here, 4 equiv. KHSO5 were necessary to achieve full conversion. Otherwise, a hexamethyl-biphenol is observed as minor side-product. Covalently supported iron phthalocyanine complexes also showed activity in the oxidation of phenols bearing functional groups (alcohols, double bonds, benzylic, and allylic positions) [135]. Besides, silica-supported iron phthalocyanine catalysts were reported in the synthesis of menadione [136]. 

Highly diasteroselective and chemoselective reductions may be performed on the hydroxy functions of (r/6-arene)-tricarbonylchromium complexes. Treatment of the chromium-complexed benzylic alcohol 29 with triethylsilane and boron trifluoride etherate in dichloromethane at —78° to 0° gives only diastereomer 30 in 75% yield (Eq. 40).181 In a similar fashion, treatment of the complexed exo-allyl-endo-benzylic alcohol 31 with an excess of Et3SiH/TFA in dichloromethane at room temperature under nitrogen produces only the endo-aflyl product 32 in 92% yield after 1.5 hours (Eq. 41). It is noteworthy that no reduction of the isolated double bond occurs.182... 

Vinylogs of benzylic alcohols, e.g. cinnamyl alcohol, undergo easy saturation of the double bond by catalytic hydrogenation over platinum, rhodium-platinum and palladium oxides [39] or by reduction with lithium aluminum hydride [609]. In the presence of acids, catalytic hydrogenolysis of the allylic hydroxyl takes place, especially over platinum oxide in acetic acid and hydrochloric acid [39]. 

Tertiary benzylic nitriles are useful synthetic intermediates, and have been used for the preparation of amidines, lactones, primary amines, pyridines, aldehydes, carboxylic acids, and esters. The general synthetic pathway to this class of compounds relies on the displacement of an activated benzylic alcohol or benzylic halide with a cyanide source followed by double alkylation under basic conditions. For instance, 2-(2-methoxyphenyl)-2-methylpropionitrile has been prepared by methylation of (2-methoxyphenyl)acetonitrile using sodium amide and iodomethane. In the course of the preparation of a drug candidate, the submitters discovered that the nucleophilic aromatic substitution of aryl fluorides with the anion of a secondary nitrile is an effective method for the preparation of these compounds. The reaction was studied using isobutyronitrile and 2-fluoroanisole. The submitters first showed that KHMDS was the superior base for the process when carried out in either THF or toluene (Table I). For example, they found that the preparation of 2-(2-methoxyphenyl)-2-methylpropionitrile could be accomplished h... 

When the double bond of the allyl fragment is part of a benzene ring, i.e. when benzyl alcohols are used, a 1,3-benzyl shift takes place instead of the Claisen rearrangement (see Section 5.I.3.).28... 

The presence of the double bond (carbonyl group C 0) markedly determines the. chemical behavior of the aldehydes. The hydrogen atom connected directly to the carbonyl group is not easily displaced. The chemical properties of the aldehy des may be summarized by (1) they react with alcohols, with elimination of H2O, to form ace t i (2) they combine readily with HCN to form cyanohydrins, (3) they react with hydroxylamine to yield aldoximes (4) they react with hydrazine to form hydrazones (5) they can be oxidized lulu fatty acids, which contain die same [lumber of carbons as in the initial aldehyde 5) they can be reduced readily to form primary alcohols. When bcnzaldchydc is reduced with sodium amalgam and HjO, benzyl alcohol C,f l - -C f I Of I is obtained. The latter compound also may be obtained by treating benzaldehyde with a solution of cold KOH in which benzyl alcohol and potassium benzoate are produced. The latter reaction is known as Cannizzaro s reaction. 

Intramolecular protonation on the more hindered face of a steroid from a neighbouring hydroxyl group best explains a reversal of diastereoselectivity in the Birch reduction of styrene double bonds.266 The kinetics and product distribution of lithium metal reduction of benzaldehyde to benzyl alcohol in THF have been studied electron transfer from Li to PhCHO occurs in a slow step, but absorption of the PhCHO onto the metal surface is also crucial in determining the overall kinetics. The proposed mechanism successfully accounts for the formation of minor products, benzoin and... 

Unsubstituted aliphatic alcohols cannot usually be a-metalated by treatment with strong bases (to yield a dianion). Dilithiated methanol has been prepared by treatment of Bu3SnCH2OH with two equivalents of BuLi, and can be alkylated at carbon [287]. Treatment of allyl alcohol with excess BuLi/TMEDA in pentane at room temperature does not lead to formation of the dianion of allyl alcohol but to addition of BuLi to the C-C double bond [288] (Scheme 5.33). Benzylic alcohols, on the other hand, can be deprotonated twice and, depending on the substitution pattern at the... 

Again use Tollens reagent. Alcohols (such as benzyl alcohol) do not react. Both compounds are ketones, but 2-cyclohexenone has a carbon-carbon double bond and will be easily oxidized by potassium permanganate (the purple color of the KMn04 will turn to the brown color of Mn02). The saturated ketone, cyclohexanone, will not react. 

Possible competitive reactions (e.g., cycloadditions on the double bond) proceed only very slowly with diazotoluene dibenzyl ether is produced by the reaction with water so that strictly anhydrous conditions are not necessary. Similarly, the presence of traces of water does not interfere with the esterification with the aid of N,N -dicyclohexyl-0-benzylisourea, which reacts with water with the production of benzyl alcohol. The reagent is synthesized from dicyclohexylcarbodiimide and benzyl alcohol with copper(I) chloride as the catalyst. The esterification proceeds according to Scheme 5.16. 

These observations are not surprising since the presence in the bridges of an even or odd number of atoms, or of a cis or trans double bond, determines the orientation of the reactive benzyl alcohol ends, and, in turn, the clockwise or counter-clockwise sense of the cyclization, as illustrated in Fig. 7. 

Some additives, like benzyl alcohol, are added for a double action. Benzyl alcohol 0.9% is widely used as a bactericide. In addition, benzyl alcohol reduces radiolysis in radiopharmaceuticals and thus acts as a stabilizer. 

Maruoka and co-workers reported a conceptually new MPV reduction system based on bidentate Lewis-acid chemistry [29]. The initial formation of bidentate aluminum catalyst 9 derived from (2,7-dimethyl-l,8-biphenylenedioxy)bis(dimethylalu-minum) (8 prepared from 2,7-dimethyl-l,8-biphenylenediol and 2 equiv. MesAl) and i-PrOH (4 equiv.), followed by treatment of benzaldehyde with the in situ generated (2,7-dimethyl-l,8-biphenylenedioxy)bis(diisopropoxyaluminum) (9) at room temperature instantaneously produced the reduced benzyl alcohol almost quantitatively (Table 2, entry 2). Even with 5 mol% catalyst 9 the reduction proceeds quite smoothly at room temperature to furnish benzyl alcohol in 81 % yield after 1 h (Table 2, entry 3). This remarkable efficiency can be ascribed to the double electrophilic activation of carbonyls by the bidentate aluminum catalyst (Sch. 7). 

---