Hydrochloric Acid → 4,5-Dichloro-9-anthraldehyde

Beteiligte Stoffe

Reaktionsschritte

1,8-Dichloroanthracene prepared by the method of H. O. House et al. (J. Org. Chem. 38 1167 (1973)). A 3 L 3-neck flask fitted with overhead mechanical stirrer, thermometer, condenser, and N2 line was charged with 1,8-dichloroanthracene (17.3 g, 70 mmol) and CH2Cl2 (1500 mL). After further cooling with a salt-ice bath to 5°, SnCl4 (Aldrich, 98%, 36.5 g, 0.14 mol, 16.4 mL), was added in one portion to the reaction. No temperature change occurred. The pot temperature was kept below 5°, and 1,1-dichloromethylmethylether (Aldrich, 16.09 g, 0.14 mol, 12.60 mL) was added dropwise over 1 h. The resulting suspension was warmed slowly to reflux (37°). Considerable HCl gas evolution occurred during the warming and the early part of the reaction at 37°. The reaction mixture was then cooled to 10° and hydrolysed by careful addition of 1 L of cold H2O. After 4 h the layers were separated and the organic layer filtered, dried with anhydrous Na2SO4 (Mallinckrodt, 100 g) and filtered again and the volume reduced to 100 mL. The clear yellow solution was passed through a 1000 g plug of SiO2 using PhCH3 as the eluting solvent with 500 mL fractions. This chromatography separated unreacted 1,8-dichloroanthracene (11 g, 63%) from the aldehyde and a more polar product. Fractions containing the aldehyde were combined and the PhCH3 removed, to give 5.83 g (21%) of 4,5-dichloro-9-anthracenecarbaldehyde mp 218°-220°, (PhCH3 /CH3OH), (C,H,Cl), (lit. 224°-226°, E. L. Stogryn, J. Med. Chem. 17 563 (1974)).

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