Pyrrolidine → 3-(3,4-dihydro-7-hydroxy-2-methyl-4-oxo-8-propyl-2H-1-benzopyran-2-yl)propanoic acid

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Reaction Steps

To a mixture of 20.0 g (103 mmole) of 2,4-dihydroxy-3-propylacetophenone and 15.5 g (134 mmole) of methyl levulinate in 100 ml of dry toluene was added by syringe 21.5 ml (ca. 260 mmole) of pyrrolidine. After stirring for one hour the solution was heated on a steam bath for four hours and allowed to cool. The toluene solution was washed with water and 2N NaOH. The basic solution was acidified and extracted with diethyl ether, which in turn was extracted with saturated sodium bicarbonate. The basic aqueous extract was neutralized with dilute hydrochloric acid and again extracted with diethyl ether. After drying, the solution was concentrated at reduced pressure to an oil which crystallized to the title compound, m.p. 152°-153°.

Provenance & Evidence