CHEMBRDG-BB 7109536 synthesis

Yield:107057-96-5 86%

Reaction Conditions:

with poly(4-vinylpyridinium) hydrogen sulfate (PVPHS) in neat (no solvent); for 0.2 h;Sonication;Pechmann Condensation;

Steps:

General procedure for the preparation of coumarins

General procedure: In a 25-mL batch reactor equipped with a distillation condenser the mixture of phenols (1.0 mmol), β-keto esters (2.0 mmol) and PVPHS (10 mg, 0.02 mmol) was stirred and irradiated with ultrasonic of low power (with a frequency of 35 kHz and a nominal power 200 W). The temperature of the reaction mixture started to rise. After 2 min of irradiation, the ultrasound source was switched off. Since the Pechmann reaction proved to be exothermic, the reaction mixture continued to rise in temperature. After completion of the reaction (monitored by TLC), ethanol was added to the reaction mixture and the catalyst was recovered by filtration. The filtrate was concentrated in vacuum, and the crude product was washed with water, dried and slowly recrystallized in ethanol or ethanol-water system. The melting point, IR, ¹H NMR and mass spectroscopic techniques were used to analyze the products and compared with the authentic samples. 5-Hydroxy-3,4,7-trimethylcoumarin (Table 3, entry 4) white crystals, mp: 249-251 °C (ethanol) (lit. mp: 249 °C) [57]; IR (KBr): ν = 3216, 3028, 2986, 1675, 1620, 1283, 1120, 1062 cm^-1; ¹H NMR (300 MHz, DMSO-d6) δ = 2.04 (s, 3H, CH₃), 2.27 (s, 3H, CH₃), 2.53 (s, 3H, CH₃), 6.57 (s, 2H, ArH), 10.32 (brs,1H, OH). MS (EI, 70 eV): m/z = 204 [M⁺].

References:

Khaligh, Nader Ghaffari [Ultrasonics Sonochemistry,2013,vol. 20,# 4,p. 1062 - 1068]