Acetic Acid → ethyl 7-tert-butyl-6-chloro-2-(trifluoromethyl)-2H-chromene-3-carboxylate

Participants

Reaction Conditions

Reaction Steps

A one liter three-neck flask equipped with mechanical stirrer and gas inlet tube was charged with the ester (Step 2) (100 g, 0.3 mole) and acetic acid (300 mL). While cooling (water bath) the reaction mixture, chlorine gas (37.6 g, 0.53 mole) was added which caused the temperature to rise to 48° C. After stirring for two hours, the reaction was cooled in an ice-water bath to 15° C. Zinc powder (19.5 g, 0.3 mole) was added in one portion which caused the temperature to rise to 72° C. After cooling to room temperature additional zinc powder (5.0 g, 0.08 mole) was added and the mixture was stirred for 0.5 hour longer. The crude mixture was filtered through diatomaceous earth and was concentrated in vacuo yielding an oil. The oil was dissolved in ethyl acetate (700 mL) washed with brine-water (1:1, 1 L) and brine (0.5 L). The resulting aqueous phase was extracted with ethyl acetate (700 mL). This ethyl acetate phase was washed with brine-water (1:1, 1 L) and brine (0.5 L). The combined organic phases were dried over MgSO4, filtered and concentrated in vacuo yielding the title compound as a yellow oil (116 g, 106%). This material, which contained some entrained ethyl acetate, was of suitable purity to be used in subsequent steps without further purification.

Provenance & Evidence