Naphthacene → 5-Naphthacenecarboxaldehyde

Beteiligte Stoffe

Reaktionsschritte

To a 3-necked RB flask equipped with overhead mechanical stirrer, condenser, addition funnel, N2 inlet line with bubbler was added N-methylformanilide (Aldrich, 89.21 g, 0.66 mol, 81 mL) and o-dichlorobenzene (Aldrich, 200 mL). The mixture was cooled to 10° with an ice bath. Phosphorus oxychloride (Aldrich, 101.21 g, 0.66 mol, 60 mL) was then added dropwise to the solution not allowing the reaction temperature to rise above 10°. The reaction mixture was then allowed to warm to RT. Solid naphthacene (Cambridge Chemical, Inc., 50 g, 0.22 mol) was then added in five portions over 5 min. The reaction mixture was warmed slowly to 80° (the mixture turns from purple to an almost black color). The reaction was stirred at 80° for 12 h, cooled, poured into ice water (2 L) and stirred an additional 12 h at RT. The mixture was then filtered. The organic layer in the filtrate was dried (Na2SO4) and applied to a plug of SiO2 (500 g) and eluted first with PhCH3 followed by CH2Cl2. The appropriate fractions were combined and the solvent removed by rotary evaporation. Recrystallization (CH2Cl2 /EtOAc) gave 17.5 g (31.1% yield) of naphthacene-5-carbaldehyde, mp 163°-164° (Lit. 164°, N. P. Buu-Hoi et al., Recueil 76 674 (1957)), (C, H). The solid from the filtration of the crude reaction mixture was washed with a large volume of CH3OH (5×200 mL), dissolved in THF (4 L) and passed through a plug of SiO2 (500 g) using an additional 2 L of THF as eluting solvent. The solvent was reduced to a volume of 300 mL and then diluted to 800 mL with EtOAc. The solvent volume was reduced to 250 mL. After filtration and drying 10.90 g (17.4% yield) of naphthacene-5,11-dicarbaldehyde, mp 247°-250°, (C, H).

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