反应详情

A solution of glyoxylic acid ethyl ester, polymer form (2.02 g, 8.9 mmol) and (3-methoxy-1-methylene-allyloxy)-trimethyl-silane (1.9 ml, 8.9 mmol, Danishefsky's diene) in benzene (12 ml) was placed under nitrogen. Zinc chloride (0.5N in tetrahydrofuran, 8.9 ml, 4.45 mmol) was added and the reaction stirred at ambient temperature for 72 h. The mixture was concentrated in vacuo, diluted with ethyl acetate (100 ml) and washed with 1 N hydrochloric acid (20 ml), saturated sodium bicarbonate (20 ml), and brine (20 ml). The organic layer was dried (Na2SO4), filtered, and the solvent evaporated in vacuo. The residue was purified by silica gel chromatography using a mixture of ethyl acetate/hexane (1:2) as eluant. Pure fractions were collected and the solvent evaporated in vacuo which afforded 1.2 g (75%) of 4-oxo-3,4-dihydro-2H-pyran-2-carboxylic acid ethyl ester as an oil.

1. concentrationThe mixture was concentrated in vacuo
2. additiondiluted with ethyl acetate (100 ml)
3. washwashed with 1 N hydrochloric acid (20 ml), saturated sodium bicarbonate (20 ml), and brine (20 ml)
4. dry with materialThe organic layer was dried (Na2SO4)
5. filtrationfiltered
6. customthe solvent evaporated in vacuo
7. customThe residue was purified by silica gel chromatography
8. additiona mixture of ethyl acetate/hexane (1:2) as eluant
9. customPure fractions were collected
10. customthe solvent evaporated in vacuo which