Preparation by reaction of propionitrile with phlo-roglucinol (Hoesch reaction);
Preparation by reaction of propionic anhydride with phloroglucinol
in the presence of concentrated sulfuric acid (one drop) at 130° for 5 min ? (65%)
in the presence of Amberlite IR-120 (cation exchange resin sulfonic acid ? type) at 160° for 2–3 h (42%). N.B.: Zeokarb 225 was found to be as effective
in the presence of boron trifluoride etherate at 10° (62–65%)
Preparation by reaction of propionyl chloride with phloroglucinol
in the presence of aluminium chloride in nitrobenzene/carbon disulfide ? solution (76%), in nitrobenzene at 60° (55%) or without solvent at 50° (70%)
in the presence of boron trifluoride etherate at 10° (compound ? 3) (62–65%).
General procedure: Anhydrous AlCl3 (4 eq.) was slowly added to a stirred suspension of resorcinol (1 eq.) in CS2. Subsequently, nitrobenzene was added dropwise over 30 minutes. The reaction mixture was refluxed at 55 °C for 30 min. Next, propionyl chloride (1 eq.) dissolved in nitrobenzene was slowly added over 30 min and the reaction mixture continued to be heated for 30 min. Upon completion of the reaction, the mixture was allowed to cool to room temperature with stirring, followed by slow pouring into an ice water bath. 3M HCl was added to quench the reaction. The organic solvent was removed by distillation under reduced pressure and the resulting oily residue was extracted with Et2O. After extraction, Et2O was removed by evaporation and the crude product was purified by fast chromatography (eluent: petroleum ether (boiling point 50-70 °C)/ethyl acetate, ratio tapered from 5:1 to 3:1).
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[2] European Journal of Medicinal Chemistry, 2014, vol. 85, p. 621 - 628
[3] Australian Journal of Chemistry, 2005, vol. 58, # 7, p. 551 - 555
[4] European Journal of Medicinal Chemistry, 2018, vol. 155, p. 255 - 262
[5] Bioorganic and Medicinal Chemistry, 2006, vol. 14, # 13, p. 4402 - 4409
