O-Methoxyacetophenone

Scheme 32 Ortho photocycloaddition of p- and o-methoxyacetophenone to ethyl vinyl ether and vinyl acetate.

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-. ... 

Ozone or performic acid readily converts 106 into the aldehyde 107, which then undergoes cyclodehydration to 108 with PPA. ° Thus, 4-allyloxy-2-hydroxy-o>-methoxyacetophenone gives (Claisen) 3-allyl-2,4-dihydroxy-oj-methoxyacetophenone, then (with ozone) aldehyde (109) and 4-hydroxy-5(methoxyacetyl)benzofuran (110). 

The reaction of a-chloro carbonyl compounds with ammonia is not always successful, for example, w-chloro-o-methoxyacetophenone and w-chloro-o,p-dimethoxyacetophenone yield only resinous products (236), but in these cases potassium phthalimide may be used for the ammonation to the a-amino carbonyl compound. This last method was developed by Gabriel (116) and co-workers (187). 

The catalytic activity of AITPApva-peg, CuTPApva-peg, AITSApva-peg, and CuTSApvA-PEG catalysts in anisole acylation is displayed in Table 1. Although o-methoxyacetophenone was detected, the main product of the reaction was p-methoxyacetophenone (/7-MAP), with selectivity higher than 90%. Only monoacylated products were detected. 

Fig. 1. (A) NMR spectrum ( H decoupled) of tritiated o-methoxyacetophenone (0-CH3O-C6H4COCH2T, llpCi) with a proton/tritium cryoprobe at 533.5MHz,...

In the presence of AcOH, benzoquinone (as oxidarrt) and o-methoxyacetophenone or Ph3P as ligands, Pd(tfa)3 catalyses selective allylic oxidation of olefins into their allyl acetates [McMurry Kocovsky Tetrahedron Lett 25 4187 1984],... 

Figure 1 NMR spectra of tritiated o-methoxyacetophenone (o-MeO-C6H4COCH2T, 68pCi) observed (A) at 320.13MHz with a 5 mm duai-proton/tritium probe, (B) at 533.5 MHz with a 5 mm ieak-proof seiective excitation proton/tritium probe, (C) at 533.5 MHz with the 5 mm seiective excitation proton/tritium cryoprobe, and (D) the same compound at iower activity (11 pCi) using the 5 mm seiective excitation proton/tritium cryoprobe at 533.5 MHz. (Reproduced with permission from Bioxsidge JP, Garman RN, Giiiies DG, Jones JR, and Lu SY (2004) Deveiopment and appiication of a tritium cryo-probe H NMR studies at the microcurie (megabecquerei) ievei of radioactivity, in Dean DC, FiierCN, and McCarthy KE (eds.) Synthesis and Application of Isotopically Labelled Compounds, voi. 8. Chichester John Wiiey Wiiey.)...

Reductive alkylation of o-methoxyacetophenone is the first step of a controlled synthesis of 2-alkylcyclohexenones reported by Mander (Scheme... 

Preparation by reaction of acetyl chloride (2 mol) with o-methoxyacetophenone (1 mol) in the presence of aluminium chloride (2 mol) in boiling carbon disulfide for... 

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