The photochemistry of five 1,3-dicarbonyl compounds, substituted at the 1-position with an o-methylphenyl group, has been investigated. Compounds 5a-c cyclize upon irradiation to give tetralones 6a and 6c and octahydroanthracene derivative 6b, respectively. Compounds 5d and 5e do not form similar photoproducts. Diketone 5c is the most efficient in this reaction, indicating that the reaction probably occurs via the keto tautomer. A mechanism involving initial y-hydrogen abstraction followed by interception of the resulting 1,Cbiradical by the second carbonyl group is proposed.
mA (current density: 1.6 A/dm2). After 8.0 F/mol of electricity was passed, the reaction mixture was poured into 100 mL of a saturated sodium chloride solution and extracted with three 50-mL portions of ether. The combined ethereal solution was dried over anhydrous magnesium sulfate, filtered, and concentrated to give an oily material, which was then fractionally distilled to form almost pure 2-methyl-4-methoxyphenol (8) in 42% yield; mp 71-72 °C [lit.28 mp 71-72 °C].
5 mL) was allowed to stand at room temperature for 10 min, and the solution was then concentrated to a final volume of 1 mL. Acetone (30 mL) was added, and the precipitate was removed by suction filtration. The filtrate was taken to dryness, and the product was obtained as a powder from EtOH-CeHg: mp 109-111 °C; yield 63 mg (58%).
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