Methoxy Methoxyacetophenones

Methoxyacetonitrile, 21, 79 u-Methoxyacetophenone, 21, 79 5-(3-Methoxy-4-hydroxybenzal)-creatinine, 22, 90, 93 5-(3-Methoxy-4-hydroxybenzyl)-CREATININE, 22, 90... 

Anisole under the same conditions gives only -methoxyacetophenone, even though the acetyl cation undoubtedly reacts faster with the methoxy group than with the benzene ring. Since no stabilizing car-bonium ion is split off the former reaction remains reversible and ineffective, while the nuclear substitution is pushed to completion by the removal of a proton. 

Fig. 1. Concentration dependence of the efficiency of energy transfer A, p-methoxy-acetophenone o, m-methoxyacetophenone A, 3,4-methylenedioxyacetophenone , thioxanthone. (From Chapman and Wampfler48 with permission of the American Chemical Society.)...

Ethyl 3-phenylpropynoate and a>-methoxyacetophenone condense in the presence of ethoxide ion to give 5-methoxy-4,6-diphenylpyran-2-one and clearly much variation in substituents is possible in this synthesis. 

The methoxy group donates electrons to the carbonyl carbon by resonance, making it less electrophilic and less reactive. Therefore, the equilibrium constant for cyanohydrin formation is larger for acetophenone than for p-methoxyacetophenone. 

It has, for instance, been shown with these methods that the dependence of the p Ka of the lithium enolate of o-methoxyacetophenone on the concentration in diluted THF was a consequence of its aggregation, and that an important internal solvation effect of the lithium cation by the oxygen of the methoxy appendage was taking place in the dimer249. 

In the lithium and cesium enolates of o-methoxyacetophenone, the methoxy oxygen coordinates with the smaller lithium cation but not with the cesium cation . Other examples of lithium enolate chemistry include a thermochemical analysis of the aldol reaction of lithiopinacolonate with pivalaldehyde and a comparison of the proton affinities and aggregation states of lithium alkoxides, phenolates, enolates, -dicarbonyl enolates, carboxylates and amidates. Although the lithium enolate of cyclopropanone itself remains unknown, derivatives (accompanied by their aUenoxide isomer) have been implicated in the reaction of a-(trimethylsilyl) vinyl lithium with CO. That both species are seemingly formed is surprising because cyclopropanone enolate is expected to be much less stable than its acyclic isomer cyclopropene is less stable than allene by almost 90 kJmol-. ... 

Methoxyacetonitrile, 21, 79 cu-Methoxyacetophenone, 21, 79 2-Methoxy-i,4-naphthoquinone, 21, 57 Monel metal stirrer, 20, 99 Monoperphthalic acid, 20, 70 Myristic acid, 20, 69 Myrtle wax, 20, 68... 

---