Allyl bromide → 2'-Allyloxyacetophenone

Participants

Reaction Steps

2′-Hydroxyacetophenone (1I-3) (14.0 g, 0.103 mol), allyl bromide (20.4 g, 0.169 mol) and potassium carbonate (14.2 g, 0.103 mol) in acetone (140 ml) were refluxed for 16 h. The solvent was removed under reduced pressure and water was added. The layers were extracted with ether and the organic extracts were washed with water, dried over magnesium sulfite and concentrated under reduced pressure leaving 17.9 g of 2′-allyloxyacetophenone as a colorless oil. 8.6 g of allyl ether thus obtained was refluxed in 1,2-dichlorobenzene (40 ml) in an oil bath heated at 210° C. for 18 h. The solvent was removed under reduced pressure to give 8.9 g of 3′-allyl-2′-hydroxyacetophenone. Without purification, the product was dissolved in DMF (60 ml) and was added dropwise to a suspension of sodium hydride (60% oil dispersion, 2.4 g, 0.06 mol) in DMF (25 ml) at a rate keeping the reaction temperature between 40 to 45° C. After stirring for additional 20 min, a solution of benzyl bromide (8.6 g, 0.05 mol) in DMF (10 ml) was added dropwise. After 2 h and 4 h, each 0.7 g of additional benzyl bromide was added. After 6 h, the reaction mixture was poured into ice water and extracted with ether. The organic layer was washed with water, dried over magnesium sulfate, and the solvent was removed to give 14.0 g of an orange oil. This was purified by 250 g of silica gel chromatography (ethyl acetate/hexane=1:4) to give compound (II-4) (9.6 g) as a pale yellow oil.

Provenance & Evidence