Benzaldehyde methoxide ions

Large concentrations of halide ions, preferably iodide, favour the formation of /ra/i5-stilbene from benzaldehyde and benzyltriphenylphosphonium halides in methanol with methoxide as base, whereas large concentrations of methoxide ions slightly favour formation of the m-isomer. These effects have been explained by the preferential solvation of P+ by halide ions, leading to greater reversibility of betaine formation. Methoxide ions, on the other hand, are preferentially solvated by methanol. 

In organic solvents the acidity functions H corresponding to hydrogen dissociation from neutral indicator acids were reported for solutions of alkali metal alkoxides in various alcohols (2), using nitroanilines (21), aminobenzenecarboxylic acids (22), or indols (23) as indicators. For addition reactions of methoxide and ethoxide ions to neutral indicator acids, acidity functions J (also denoted as Hr) based on use of nitrobenzenes (21) and a-cyanostilbenes (18) as indicators in methanol and dimethylsulfoxide-methanol and -ethanol mixtures were reported. Recently (24) the acidity function J- (denoted as Jm) was derived for methoxide ion solutions in methanol using substituted benzaldehydes as indicators. These scales involve arbitrary choice of water as the solvent for determination of the dissociation constant of the anchoring acid. 

The acidity function J (denoted as Jm) for addition of methoxide ions to benzaldehydes (24) increases with base concentration much less steeply than acidity function obtained for additions of methoxide ion to polynitrobenzenes (21) or a-cyanostilbenes (18). No single acidity scale can be applied to strongly basic media, and a given acidity scale can be used only in connection with reaction of the same type. 

One of the reactions involving hydride transfer, which has synthetic importance in solution chemistry, is the Meerwein-Ponndorf-Verley reduction of carbonyl compounds by hydride transfer from alkoxide ions. Similarly, it has been found possible to reduce formaldehyde, benzaldehyde, 2,2-dimethylpropanal and 1-adamantylcarboxaldehyde with methoxide ions in the gas phase (Ingemann el al., 1982b). The reaction trajectory of the hydride transfer from the methoxide ion to formaldehyde has also been studied by ab initio calculations (Sheldon et al., 1984b). 

Secondary amines reacted to form hydrazines in yields of 90% and better. Aniline can be converted to phenylhydrazine. Sometimes the addition was followed by the elimination of water rather than the aminated nucleophile. For example, treatment of 3,3-pentamethyleneoxaziridine with methoxide ion produced cyclohexanone oxime (9-methyl ether. Formanilide reacted with 3-phenyloxaziridine in the presence of sodium ethoxide to produce benzaldehyde phenyUiydrazone. " Of considerable interest is the reaction of Schiff bases with these oxaziridines to produce diaziridines. Other examples are given in Schmitz recent review. One intramolecular version of this kind of amination is known oxaziridine 57 was converted to benzophenone and 5,6-dihydro-4H-l, 2-thiazine 58 upon heating. ... 

Gas-phase transfers of hydride from methoxide to C02, CS2 and S02 have been observed by the flowing afterglow technique (Bierbaum et al., 1984) and by Fourier transform ion cyclotron resonance spectroscopy (FT-ICR) (Sheldon et al., 1985). With aldehydes and ketones, the normal gas-phase reaction with methoxide is enolate formation, but FT-ICR methods have been used to demonstrate reduction of non-enolizable aldehydes including benzaldehyde, pivalaldehyde, and 1-adamantylaldehyde. 

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