1,2,4-trimethoxy-3-methyl-anthraquinone. page 443

N-bromosuccinimide

dibenzoyl peroxide

A mixture of 1,2,4-trimethoxy-3-methyl-anthraquinone (3.029 g, 9.7 mmol), N-bromosuccinimide (1.8 g, 10.1 mmol) and dibenzoyl peroxide (84 mg) was refluxed for 10 h in CCl₄ (200 cm³).   The suspension was filtered with charcoal and Celite through flash silica gel (10 g), washing with CCl₄ (2 x 30 cm³). Evaporation gave a yellow solid (3.53 g, 93% yield).

A larger scale reaction (7.5 g) gave 8.8 g, (93% yield) of product.

2-Bromomethyl-1,3,4-trimethoxy-anthraquinone was recrystallised from chloroform by adding 60/80 petrol to give yellow crystals, mp. 134 ºC, or from acetic acid, mp. 135-136 ºC (lit: Hirose Y, yellow needles, mp. 136-137 ºC (acetic acid). Benzylic bromination of 3-methyl-1,6,8-trimethoxyanthraquinone with N-bromosuccinimide has been described (Falk, Tran, 1996)

δH (CDCl₃) 8.21m (2H), 7.78m (2H), 4.69s (2H), 4.19s (3H), 4.09s (3H), 3.99s (3H)

EI m/z (%),  392 (26), 390 (26), 311 (64), 86 (30), 84 (48), 49 (100)

Hirose Y, Chem Pharm Bull, 1960, 8(5), 417-426

Falk H, Tran TNH, Monatsch Chem 1996, 127(6) 717-723

DOI: 10.1007/BF00817262