4 -methoxyacetophenone

S)-Tricarbonyl(2-methoxyacetophenone)chromium is a starting material which provides remarkable substrate-induced stereoselectivity. Thus, its conversion into a boron enolate and subsequent addition to aldehydes delivers the chromium complexes 7 and 8 with diastereomeric ratios of 92 8 to 95 559. 

Compounds (99) and (100) are thought to be formed by addition of cyanide ion to the ring ortho to the carbonyl, followed by protonation at oxygen, aromatization by tautomerization, hydrolysis of the nitrile, and lactonization upon acidification. The photolysis of 2-methoxyacetophenone, on the other hand, results in rearrangement to 3-methoxyacetophenone ... 

To obtain information concerning the pathway of this rearrangement, 2-methoxyacetophenone was photolyzed in the presence of cyanide ion in deuterium oxide to yield (101) ... 

Et2Zn) (20 (iL, 0.02 mmol, 1.0 M in hexanes) was added at the same temperature. After stirring for 30 minutes at — 20 °C, a solution of 2-hydroxy-2 -methoxyacetophenone (322.3 mg, 2.0 mmol) in tetrahydrofuran (4.7 mL) was added. The resulting mixture was cooled to —30 °C and hydrocinnamaldehyde (1.0 mmol) was added and stirred at the same temperature. The stirring was continued for 20 hours at this temperature (TLC hexane/ethyl acetate = 2/1, iyw-diol R< 0.44, anti-diol Rf = 0.26) and quenched by addition of 1 M hydrochloric acid (2mL). The mixture was extracted with ethyl acetate (x 3) and the combined organic layers were washed with brine and dried over sodium sulfate. Evaporation of solvent gave a crude mixture of the aldol products. 

Notes The purity ofEt2Zn solution and 2-hydroxy-2 -methoxyacetophenone was critical for catalytic efficiency. 

Dihydroxy-2-methoxyacetophenone from 2-hydroxy-6-methoxyacetophenone 303 2-Hydroxy-6-methoxyacetophenone (16 g) is dissolved in Jo% sodium hydroxide solution (200 ml) and cooled to 15°, at which temperature a solution of potassium persulfate (26 g) in water (500 ml) is dropped in during 4 h. The mixture is set aside at room temperature for... 

Demethoxylations involving intermolecular processes have been described, as in the reaction of 2-methoxyacetophenone in hot tetrahydrofuran containing Ti(0) (from titanium trichloride and lithium) to give 9,10-dimethyiphenanthrene aibeit in the relatively low yield of 36% (ref.99). 

The loss of a methoxyl group from the ring of an aromatic ether occurred in the regioselective photocyclisation of 2-methoxystilbene to phenanthrene in a mixture of sulphuric acid and tert-butanol with elimination of methanol (ref. 146). Phenanthrenes are also obtained by treatment of 2,2 -dialkoxystilbenes with low valent titanium. The same pathway is involved as in the reduction of 2-methoxyacetophenone to 9,10-dimethylphenanthrene referred to earlier (ref.99). 

Me ether 4 -Hydroxy-6 -methyl-2 -methoxyacetophenone. Isoacetoevernone CjoHijOj M 180.203 Plates (H2O). Mp 150°. 

Flavonoids may be synthesized by using reactions similar to those used in the chalcone synthesis. For example, the basic flavone structure (II) can be simply derived firom a Claisen condensation between ethyl benzoate and 2-methoxyacetophenone, followed by treatment with HI ... 

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