4-bromo-3,5-dimethylbenzaldehyde

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 4-bromo-3,5-dimethyl-benzaldehyde (8.15 g, 38.25 mmol), p-toluenesulfonic acid (50 mg) and 1,3-propanediol (9.5 mL) in toluene (100 mL) is heated to 110° C. for 3 h. The reaction flask is equipped with a Dean-Stark apparatus and heating is continued at 110° C. for 16 h. The reaction mixture is cooled to rt, washed with sat. aq. NaHCO3 and the solvent is removed in vacuo. The crude product is purified by CC on silica gel eluting with heptane:EA 9:1 to give 2-(4-bromo-3,5-dimethyl-phenyl)-[1,3]dioxane (5.97 g) as a colourless oil. The reaction flask is equipped with a Dean-Stark apparatus heating washed with sat. aq. NaHCO3 the solvent is removed in vacuo The crude product is purified by CC on silica gel eluting with heptane:EA 9:1

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 4-bromo-3,5-dimethyl-benzaldehyde (8.15 g, 38.25 mmol), p-toluenesulfonic acid (50 mg) and 1,3-propanediol (9.5 mL) in toluene (100 mL) is heated to 110° C. for 3 h. The reaction flask is equipped with a Dean-Stark apparatus and heating is continued at 110° C. for 16 h. The reaction mixture is cooled to rt, washed with sat. aq. NaHCO3 and the solvent is removed in vacuo. The crude product is purified by CC on silica gel eluting with heptane:EA 9:1 to give 2-(4-bromo-3,5-dimethyl-phenyl)-[1,3]dioxane (5.97 g) as a colourless oil. The reaction flask is equipped with a Dean-Stark apparatus heating washed with sat. aq. NaHCO3 the solvent is removed in vacuo The crude product is purified by CC on silica gel eluting with heptane:EA 9:1

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 2,5-dibromoxylene (8.0 g, 30.3 mmol) in diethyl ether (120 mL) is cooled to −78° C. and then treated with n-buthyllithium (20 mL, 1.6 M in hexane). After stirring for 40 min, DMF (6 mL) is slowly added. The mixture is warmed to rt and stirred for 1 h. The mixture is cooled again to −78° C. before another portion of n-butyllithium (5 mL) is added. The reaction mixture is allowed to warm to rt and stirred for another hour. The reaction is quenched by adding 5% aq. HCl. The mixture is extracted with EA, and the extract is concentrated in vacuo. The crude product is purified by CC on silica gel eluting with heptane:EA 5:1 to give 4-bromo-3,5-dimethyl-benzaldehyde (8.2 g) as a white soft solid. stirred for 1 h is added to warm to rt stirred for another hour The reaction is quenched by adding 5% aq. HCl The mixture is extracted with EA the extract is concentrated in vacuo The crude product is purified by CC on silica gel eluting with heptane:EA 5:1

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 2,5-dibromoxylene (8.0 g, 30.3 mmol) in diethyl ether (120 mL) is cooled to −78° C. and then treated with n-buthyllithium (20 mL, 1.6 M in hexane). After stirring for 40 min, DMF (6 mL) is slowly added. The mixture is warmed to rt and stirred for 1 h. The mixture is cooled again to −78° C. before another portion of n-butyllithium (5 mL) is added. The reaction mixture is allowed to warm to rt and stirred for another hour. The reaction is quenched by adding 5% aq. HCl. The mixture is extracted with EA, and the extract is concentrated in vacuo. The crude product is purified by CC on silica gel eluting with heptane:EA 5:1 to give 4-bromo-3,5-dimethyl-benzaldehyde (8.2 g) as a white soft solid. stirred for 1 h is added to warm to rt stirred for another hour The reaction is quenched by adding 5% aq. HCl The mixture is extracted with EA the extract is concentrated in vacuo The crude product is purified by CC on silica gel eluting with heptane:EA 5:1

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 4-bromo-3,5-dimethyl-benzaldehyde (8.15 g, 38.25 mmol), p-toluenesulfonic acid (50 mg) and 1,3-propanediol (9.5 mL) in toluene (100 mL) is heated to 110° C. for 3 h. The reaction flask is equipped with a Dean-Stark apparatus and heating is continued at 110° C. for 16 h. The reaction mixture is cooled to rt, washed with sat. aq. NaHCO3 and the solvent is removed in vacuo. The crude product is purified by CC on silica gel eluting with heptane:EA 9:1 to give 2-(4-bromo-3,5-dimethyl-phenyl)-[1,3]dioxane (5.97 g) as a colourless oil. The reaction flask is equipped with a Dean-Stark apparatus heating washed with sat. aq. NaHCO3 the solvent is removed in vacuo The crude product is purified by CC on silica gel eluting with heptane:EA 9:1

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 2,5-dibromoxylene (8.0 g, 30.3 mmol) in diethyl ether (120 mL) is cooled to −78° C. and then treated with n-buthyllithium (20 mL, 1.6 M in hexane). After stirring for 40 min, DMF (6 mL) is slowly added. The mixture is warmed to it and stirred for 1 h. The mixture is cooled again to −78° C. before another portion of n-butyllithium (5 mL) is added. The reaction mixture is allowed to warm to it and stirred for another hour. The reaction is quenched by adding 5% aq. HCl. The mixture is extracted with EA, and the extract is concentrated in vacuo. The crude product is purified by CC on silica gel eluting with heptane:EA 5:1 to give 4-bromo-3,5-dimethyl-benzaldehyde (8.2 g) as a white soft solid. The mixture is warmed to it stirred for 1 h is added to warm to it stirred for another hour The reaction is quenched by adding 5% aq. HCl The mixture is extracted with EA the extract is concentrated in vacuo The crude product is purified by CC on silica gel eluting with heptane:EA 5:1