Alkoxides from aromatic compounds

Carbanions from hydrocarbons, nitriles, ketones, esters, TV./V-dialkyl acetamides and thioamides, and mono and dianions from (3-dicarbonyl compounds are some of the most common nucleophiles through which a new C-C bond can be formed. This C-C bond formation is also achieved by reaction with aromatic alkoxides. Among the nitrogen nucleophiles known to react are amide ions to form anilines however, the anions from aromatic amines, pyrroles, diazoles and triazoles, react with aromatic substrates to afford C-arylation. 

Although this type of structure was first reported by Jackson et al. in 1900 for the reaction between picryl ether and potassium alkoxide, it was Meisenheimer who actually isolated and characterized the structure of such molecule for the first time in 1902. Since then, the stable or transient anionic a complexes formed from electron-deficient aromatic compounds and a variety of organic and inorganic bases" are generally called the Meisenheimer complexes. Occasionally, this type of molecule is also referred to as the Meisenheimer adducts, Meisenheimer compounds, Meisenheimer cr-adducts, Meisenheimer a complexes, Jackson-Meisenheimer adducts, or Jackson-Meisenheimer complexes. ... 

With the use of these sensitivity-enhancement approaches the stable alkoxide intermediates were indeed detected by C CP/MAS NMR spectroscopy. Isopropoxide was the first alkoxy intermediate reliably identified in propylene labeled with C in the CH= group) conversion on zeolite HY [15]. Isopropoxide exhibits the signal at 87 ppm from the labeled C atom, which is characteristic of the (CH3)2CH fragment bonded to an oxygen atom of the zeolite framework (Fig. 20). Later, other alkoxide intermediates were detected and characterized. It was demonstrated that methoxides [121,122] and ethoxides [122,123] formed from methyl and ethyl iodides and also from methanol and ethanol on H-ZSM-5 and CsX zeolites. Isobutoxy [124] and tert-butoxy [90] intermediates resulted from the dehydration of isobutanol and tert-butanol on HZSM-5. Alkoxides are highly reactive species. For example, surface methoxides are effective methylating agents in their reactions with methanol, water, ammonia, alkyl halides, HCl, CO, acetonitrile, and aromatic compounds [125]. 

Meisenheimer adduct A cyclohexadienyl derivative formed as Fewis adduct from a nucleophile (Fewis base) and an AROMATIC or heteroaromatic compound, also called Jackson-Meisenheimer adduct. In earlier usage the term Meisenheimer complex was restricted to the typical Meisenheimer alkoxide adducts of nitro-substituted aromatic ethers, for example... 

Electron-transfer from carbanions to aromatic hydrocarbons like anthracene has been known from the beginning of this century. For example, the oxidation of triphenyl carbanions, Ph3Cr, by benzophenone was described by Schlenk in 1916. Sufficiently powerful acceptors such as aromatic nitro-compounds may acquire electrons from poor donors such as alkoxides or thiolates. Butyllithium is oxidized by sterically hindered olefines, e.g., its reaction with 1,2,3,4-tetra-phenyl butadiene leads to electron transfer instead of addition. 

Asymmetric, borane-modified MPV reduction of a variety of aromatic ketones to their corresponding alcohols has recently (43) been reported using a chiral aluminum alkoxide catalyst shown in Figure 5. This compound was formed in situ from aluminum isopropoxide and (R)-l,r-binapthyl-diol in... 

Miller and coworkers prepared and investigated 2,5-bis-(sulfonyl)pyr-azines 153 as building blocks and studied their nucleophilic aromatic substitution reactions (Scheme 76) (13TL1938). In most cases, such as with phenols, alkoxides, anilines, aliphatic amines, heterocychc amines, and a carbanion formed from diethyl malonate with sodium hydride, only the monosubstituted sulfonylpyrazine was obtained. Reactions with two equivalents of either thiols or thiophenols, however, yielded only bis-thiopyrazines, such as compound 154, shown in Scheme 76. While the yields for the reactions with the other nucleophiles were good to high, those for reactions with aliphatic amines or anilines as the nucleophile were low to moderate. 

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