Dimethylformamide → 4-Benzyloxy-6-methyl-2H-pyran-2-one

Beteiligte Stoffe

Reaktionsschritte

Sodium hydride (2.2 gm, 50% oil, 0.0458 mol) was added portionwise to a solution of 4-hydroxy-6-methyl-2-pyrone (5 gm, 0.0396 mol) in anhydrous tetrahydrofuran. When the gas evolution ceased, anhydrous DMF (80 ml) was added, along with tetra-n-butylammonium iodide (1 gm). The solution was stirred at room temperature for 30 minutes. A solution of benzyl bromide (5.2 ml, 0.0425 mol) in HMPA (5 ml) was added. After 16 hours at room temperature, the volatile component was removed by evaporation. DMF was removed under high vacuum (1 mm Hg). The residual oil was partitioned between 10% HCl and ethyl acetate. The ethyl acetate layer was dried over magnesium sulphate and evaporated to an oil. This material was purified by flash column chromatography (Whatman LPS-II silica gel, elution gradient: 10-50% ethyl acetate:pet. ether 30-60; product Rf =0.4 at 30% ethyl acetate:pet. ether 30-60). The material was recrystallized from ether to give 4-benzyloxy- 6-methyl-2-pyrone (3.42 gm, 40% yield), m.p. 90°-91° C.; IR (KBr): 1740, 1575, 1650 cm-1, Anal. calcd. for C13H12O3 : C, 72.21, H, 5.59. Found: C, 72.31, H, 5.64.

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