2-bromo-3-methylpropiophenone synthesis

Yield:1451-83-8 59%

Reaction Conditions:

Stage #1: 3'-Methylpropiophenonewith bromine in dichloromethane; for 10 h;Inert atmosphere;
Stage #2: in dichloromethane;

Steps:

1.a.2

Step 2. 2-Bromo-3'-methylpropiophenone (1Oe). Ketone 9e (3.5 g, 0.024 mol) and methylene chloride (200 mL) were placed in a 500-mL flask equipped with a magnetic stir bar. The solution was stirred under N2 and bromine (1.21 mL, 23.6 mmol) was syringed into flask. (Note: a small amount of bromine was added to initiate the reaction; the color dissipated as reaction occurs; after reaction mixture was initiated, the remaining bromine was added over 10 min). A needle was placed in the septa to allow the hydrogen bromide gas formed in the reaction mixture to escape from the flask. After stirring for 1O h, the solution was transferred to a separatory funnel. Saturated sodium bicarbonate solution was added to basify the reaction. The mixture was filered, and the aqueous layer was extracted with methylene chloride. The organic layer was dried (Na₂SO₄) and filtered. The solvent was removed under reduced pressure to give 5.38 g of an oil. The dark orange oil was purified by flash chromatography on silica gel (3:1 hexane-methylene chloride) to afford 3.14 g (59%) of 1Oe as a pale yellow oil. ¹H NMR (CDCl₃) δ 7.86-7.79 (m, 2H), 7.42-7.32 (m, 2H), 5.35-5.25 (q, IH), 2.42 (s, 3H), 1.93-1.89 (d, 3H).

References:

WO2010/121022,2010,A1 Location in patent:Page/Page column 65-66