Base catalysed decomposition of anthracene endoperoxide

Abstract

Catalytic amounts of a weak base are sufficient to induce the decomposition of anthracene endoperoxides to anthraquinone. The mechanism has been elucidated by isolation of intermediates in combination with DFT calculations. The whole process is suitable for the convenient generation of hydrogen peroxide under very mild conditions.

Intermediates in the cleavage of endoperoxides

“…As described earlier, the mechanism of anthraquinone formation from EPOs is still a matter of debate. Very recently, we elucidated various reaction pathways by a combination of detailed experimental studies and theoretical calculations in a communication . With the simple anthracene EPO 2a as a model system, we found the quantitative formation of AQ ( 5 ) under very mild basic conditions, in the presence of only catalytic amounts of triethylamine (Experimental).…”

“…As described in literature, the endoperoxide 2a (89 mg, 0.50 mmol) was dissolved in dichloromethane (9.5 mL). The solution was subsequently submitted to five freeze‐pump‐thaw cycles, treated with a degassed solution of a catalytic amount of triethylamine in dichloromethane (0.1 M, 0.5 mL, 0.05 mmol) and stirred for 1 h at room temperature until TLC indicated complete conversion.…”

“…In analogy to literature, [12][13][14][15][16] the anthracene 1 (1 mmol) was dissolved in chloroform (100 mL) and methylene blue (0.003 g, 0.01 mmol) was added. The solution was cooled to À20°C and irradiated with a sodium lamp (400 W) under passing gaseous oxygen through the solution.…”

“…9,10-Dihydro-9,10-epidioxidoanthracene (2a). [13,14] Reaction of anthracene (1a, 178 mg, 1 mmol) for 9 h afforded the title compound in 193 mg (92%) after column chromatography (CHCl 3 /PE 3:1). White solid; m.p.…”

“…[17] Cleavage of endoperoxide 2a under anaerobic conditions. As described in literature, [14] the reaction was performed in a glove box. The endoperoxide 2a (64 mg, 0.3 mmol) was dissolved in degassed DMSO-d 6 (3 mL).…”