Liquamar ,Organon ,US,1958
8.3 parts by weight of powdered sodium in 300 parts by volume of benzene, 100 parts by weight of diethyl (1'-phenylpropyl)-malonate and 72 parts by weight of acetylsalicylic acid chloride are reacted together to form diethyl 1(o-acetoxybenzoy1)-1-(1'-phenylpropyl)malonate, which boils at 195°198°C/0.03 mm Hg.
10.3 parts of weight of diethyl 1-(o-acetoxybenzoyl)-1-(1'-phenylpropyl)malonate are dissolved in 60 parts by volume of absolute ether and to this solution are added portion. wise at 10°C, while stirring, 2.6 parts by weight of sodium methylate. The reaction mixture is stirred for 4 hours, whereupon it is poured into ice water. The ether solution is washed neutral with ice water. After having distilled off the ether, a thick oil consisting of 3-carbethoxy-3-(1'phenylpropyl)-4-oxo-dihydrocoumarinis obtained. This compound crystallized in butyl oxide and has a MP of 108°-109°C.
The 3-carbethoxy-3-(1'-phenylpropyl)-4-oxo-dihydrocoumarinmay be hydrolyzed and decarboxylated as follows. The crude product is heated to 85°C for 1/2 hour with 100 parts by volume of 5% aqueous sodium hydroxide, while agitating or stirring. To remove traces of undissolved oil, the cooled solution is treated with 1 part by weight of charcoal, whereupon it is filtrated and acidified to Congo reaction with dilute sulfuric acid. The 3-(1'phenylpropyl)-4-hydroxycoumarin formed is separated off and recrystallized in 80% ethanol, whereupon it melts at 178°-179°C according to US Patent 2,701,804.
