1,3-Propanediol → 2-(5-Bromo-2-methoxyphenyl)-1,3-dioxane

Participants

Reaction Steps

A mixture of 5-bromo-2-methoxybenzaldehyde (52.3 g, 243 mmol), 1,3-propanediol (30 ml, 31.6 g, 415 mmol), and 4-toluenesulphonic acid (0.3 g) in toluene (350 ml) was heated to reflux in a Dean-Stark apparatus for 20 h. The mixture was cooled to RT, washed with saturated NaHCO3 solution (100 ml), then the organic layer was separated and combined with a CH2Cl2 solution (100 ml). The extract was washed (brine; 50 ml), dried (Na2SO4), and concentrated in vacuo to give a brown oil (66.2 g). The crude product was distilled to afford the title compound (58.2 g) as a colourless viscous oil b.p. 115-120° C., 0.02 mmHg δH (80 MHz; CDCl3) 1.2-1.5 (1H, br m, CH2CHHCH2), 1.9-2.4 (1H, m, CH2CHHCH2), 3.78 (3H, s, OMe), 3.6-4.4 (4H, m, CH2CH2CH2), 5.76 (1H, s, OCH), 6.67 (1H, d, J 8.8 Hz, ArH ortho to OMe), 7.33 (1H, dd, J 8.8, 2.3 Hz, ArH para to acetal), and 7.68 (1H, d, J 2.3 Hz, ArH ortho to acetal); m/z (El) 274 (44%), 273 (31), 272 (45), 271 (27), 216 (34), 215 (47), 214 (35), 213 (44), 193 (34), 135 (22), and 87 (100).

Provenance & Evidence