Reactions with Aromatic Alcohols

L91 Q-Phos Imidazole-based Cyclohexyl-substiluted cataCXium phosphine BuBrettPhos 

SCHEME 20.32 Influence of the phosphine ligands in the C—O cross-coupling. 

TRANSITION METAL-MEDIATED CARBON-HETEROATOM CROSS-COUPLING 

SCHEME 20.34 Copper(I)-catalyzed synthesis of diaryl ethers. 

SCHEME 20.35 Coupling of aryl bromides with phenols. 

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The mostly commonly used approach with PCI3 (Scheme 2.85, Route I Scheme 2.87) proceeds best in the presence of a base (e.g., ammonia, trialky-lamines, pyridine). If different alcohols are to be linked, a two-step approach is recommended to avoid the formation of hgand mixtures. In large-scale reactions, no solvent is required. For a smaller setup, the reaction is conducted commonly in nonpolar solvents such as THF (tetrahydrofuran) or toluene [67]. The reaction with aromatic alcohols proceeds in three steps, in which three chlorine atoms [68] are successively replaced by phenols. 

Sahcyhc acid, upon reaction with amyl alcohol and sodium, reduces to a ring-opened ahphatic dicarboxyhc acid, ie, pimelic acid (eq. 5). The reaction proceeds through the intermediate cyclohexanone-2-carboxyhc acid. This novel reaction involves the fission of the aromatic ring to i j -hexahydrosahcyhc acid when sahcyhc acid is heated to 310°C in an autoclave with strong alkah. Pimelic acid is formed in 35—38% yield and is isolated as the diethyl ester. 

The three-component synthesis of benzo and naphthofuran-2(3H)-ones from the corresponding aromatic alcohol (phenols or naphthols) with aldehydes and CO (5 bar) can be performed under palladium catalysis (Scheme 16) [59,60]. The mechanism involves consecutive Friedel-Crafts-type aromatic alkylation and carbonylation of an intermediate benzylpalla-dium species. The presence of acidic cocatalysts such as TFA and electron-donating substituents in ortho-position (no reaction with benzyl alcohol ) proved beneficial for both reaction steps. 

Burgess reagent, (methoxycarbonylsulfamoyl)triethylammonium hydroxide, usually used for the dehydration of secondary or tertiary alcohols, was successfully employed in the formation of cyclic sulfamidates from the corresponding epoxides. It was further shown that the same reaction with aromatic epoxides resulted in the formation of seven-membered ring systems, for example, 57 (Figure 23) <2003SL1247>. 

In a gallium-mediated allyl transfer process, bulky gallium homoallylic alkoxides have been retro-allylated to generate (Z)- and ( )-crotylgallium reagents stereo- (g) specifically.195 Immediate reaction with aromatic aldehydes gives erythro- and threo-homoallylic alcohols. 

Several reactions of aromatic compounds have been investigated for their energies of activation. These include p-bromophenol, phthalate, benzoate, henzensulphonate ions, benzyl alcohol, phenylalanine and phenyl acetate, the specific rates of which range from 3-7 x 107 to 1-2 x 1010 m—1 sec-1. The energies of activation of all these reactions were found to be the same, namely, 3-5 + 0-5 kcal mole-1 (Anbar et al., 1967). This corroborates the conclusion that the rate-determining step in e a-reactions with aromatic compounds involves one and the same process, namely, the accommodation of an electron into the aromatic substrate. The subsequent reactions discussed above may be fast or slow but are not involved in the rate-determining step of the reaction of the hydrated electron. 

Ethane occurs in natural gas, from which it is isolated. Ethane is among the chemically less reactive organic substances. However, ethane reacts with chlorine and bromine to form substitution compounds. Ethyl iodide, bromide, or chlorides are preferably made by reaction with ethyl alcohol and the appropriate phosphorus halide. Important ethane derivatives, by successive oxidation, are ethyl alcohol, acetaldehyde, and acetic acid. Ethane can also be used for the production of aromatics by pyrolysis (Fig. 1). 

According to Larock and Kuo the Heck reaction of 2-iodoaniline (20) with allylic alcohols initiates cydocondensation to an imine which finally gives quinolines, in good to moderate yields, by subsequent oxidative aromatization [7]. The analogous reaction with homoallylic alcohols stops at the stage of the imine, thus resulting in benzazepines 23 (Scheme 4) [8]. The result with pyridyl-substituted homoallylic... 

In 1996, Yamamoto and Yanagisawa reported the allylation reaction of aldehydes with allytributyltin in the presence of a chiral silver catalyst.2 They found that the combination of silver and a phosphine ligand accelerates the allylation reaction between aldehydes and allyltributyltin. After this discovery, they screened several chiral phosphine ligands and found that chiral silver-diphosphine catalysts can effect the reaction in an enantioselective fashion (Table 9.1).2 For example, when benz-aldehyde and allyltributyltin were mixed in the presence of 5 mol% of AgOTf and (S)-2,2 -bis(diphenylphosphino)-1,1 -binaphthyl (BINAP), the corresponding homoallyl alcohol was obtained with 96% ee and 88% yield (Table 9.1). Generally, the reaction with aromatic aldehydes afforded the corresponding homoallyl alcohols in excellent... 

Thus, the reaction with aromatic aldehydes is second order in aldehyde and first order in hydroxide ion,31 and no deuterium becomes attached to carbon in the alcohol fragment when the reaction is carried out in deuterium oxide solution.32 It is interesting that when the reaction is carried out with benzaldehyde in the cold and in the absence of excess alkali, benzyl benzoate has been isolated.33 Although the point has not yet been settled, it seems probable that the ester is formed by a secondary reaction between the benzylate ion which is formed initially (XXIII) and two molecules of benzaldehyde 2M0... 

Considerable work was done to induce chirality via chiral auxiliaries. Reactions with aromatic a-ketoesters like phenylglyoxylates 21 and electron-rich al-kenes like dioxoles 22 and furan 23 were particularly efficient (Scheme 6). Yields up to 99% and diastereoselectivities higher than 96% have been observed when 8-phenylmenthol 21a or 2-t-butylcyclohexanol 21b were used as chiral auxiliaries [14-18]. It should be noted that only the exoisomers 24 and 25 were obtained from the reaction of dioxoles 22. Furthermore, the reaction with furan 23 was regioselective. 24 were suitable intermediates in the synthesis of rare carbohydrate derivatives like branched chain sugars [16]. Other heterocyclic compounds like oxazole 28 [19] and imidazole 29 [20] derivatives as well as acyclic alkenes 30, 31, and 32 [14,15,21,22] were used as olefinic partners. Numerous cyclohexane derived alcohols [18,21-24] and carbohydrate derivatives [25] were used as chiral... 

URANIUM HEXAFLUORIDE (10049-14-6) Violent reaction with water, steam, ethanol, producing hydrofluoric acid. Violent reaction with aromatic hydrocarbons, bromine trifluoride, Aqueous solution increases the explosive sensitivity of nitromethane and is incompatible with sulfuric acid, alkalis, alcohols, ammonia, aliphatic amines, alkanolamines, alkylene oxides, amides, epichlorohydrin, ethers, organic anhydrides, isocyanates, vinyl acetate. Attacks some plastics, rubber, and coatings. Aqueous solution attacks glass, ceramics, and silica-containing substances such as cast iron. 

Polychloromethanes can take part in photochemical electron-transfer reactions with aromatic compounds, leading (in alcohol as solvent) to products with oxygenated one-carbon substituents. It is reported that ruthenocene (95), like ferrocene, gives the corresponding ethoxycarbonyl, formyl, or ethoxymethyl compounds when irradiated with carbon tetrachloride, chloroform, or dichloro-methane, respectively. Carbazole (96) behaves in a similar way with CCI4, and the... 

Oxidations of organic substrates have also been reported. In the reaction with benzyl alcohol the reactive species is considered to be HMn04, the rate-determining step being the cleavage of the C—H bond of the alcohol. The oxidation of secondary and tertiary aromatic alcohols in acid solution proceeds via the formation of an ester ... 

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